UBC_1979_A1 Z58 - cIRcle - University of British Columbia

FACTORS
INFLUENCING THE VERTICAL DISTRIBUTIONS
<J3 TWO
INTEST.IDAL PORCELAIN
CRAB
OF
POPULATIONS
BY
DAVID Z I T T I N
B.A.,. C a l i f o r n i a
H.A. , C a l i f o r n i a
State
State
University,
University,
Humboldt, 1971
Humboldt, 1973
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOB THE DEGREE OF
DOCTOR OF
PHILOSOPHY
in
THE FACULTY OF GRADUATE STUDIES
(Department o f Z o o l o g y )
Je a c c e p t
the t h e s i s
required
as c o n f o r m i n g
standard
to the
THE UNIVERSITY OF BRITISH COLUMBIA
O c t o b e r , 1979
<§)
David
Zittia,
1979
•6
In p r e s e n t i n g t h i s
thesis
an advanced degree at
the L i b r a r y s h a l l
I
f u r t h e r agree
in p a r t i a l
f u l f i l m e n t o f the requirements f o r
the U n i v e r s i t y of B r i t i s h Columbia,
make i t
freely available
that permission
for
I agree
r e f e r e n c e and
f o r e x t e n s i v e copying o f
this
that
study.
thesis
f o r s c h o l a r l y purposes may be granted by the Head of my Department or
by h i s
of
this
representatives.
thesis
It
is understood that copying or p u b l i c a t i o n
f o r f i n a n c i a l gain s h a l l
written permission.
Department of
The U n i v e r s i t y o f B r i t i s h
2075 Wesbrook Place
Vancouver, Canada
V6T 1W5
Date
Columbia
not be allowed without my
ABSTRACT
Overlapping
on
populations
of p o r c e l a i n crabs
s e v e r a l beaches i n B a r k l e y
lower
and
limit
of the higher
t h e upper l i m i t
of
eriomerus)
were o b s e r v e d
for
years.
three
population
the
lower
What p r e v e n t e d
levels
observed
Columbia.
The
(Petrplisthes cinctipes)
population
t o be t e m p o r a l l y
from i n h a b i t i n g i n t e r t i d a l
population
Sound, B r i t i s h
were
(Petrolisthes
and s p a t i a l l y
the higher
zoned
below t h e l o w e r
and what f a c t o r s s e t t h e u p p e r l i m i t
stable
population
limit
of
of i t s
the
lower
population?
When P. e r i o m e r u s were t r a n s p l a n t e d above t h e upper
of
their
controls
This
distribution,
w h i c h were
species
population
range.
within
as l i t t l e
The c a u s e
In
contrast,
the
physical
distributional
laboratory
factors
limit
Observations
arena
lower
levels
do
of
not
of the higher
made on i n t r a s p e c i f i c
showed t h a t b o t h
similar
however, d e m o n s t r a t e d
not
demonstrated
low
i n c l u d i n g those
which
i t s population
band.
determine
lower
spacing
of
species.
a
were
the
patterns i n
s p e c i e s tended t o
which
f o r both
band.
population.
p a t t e r n s by v a r i o u s t y p e s
species,
mortalities
P. c i n c t i p e s
limit
population
than
a s 0.3 m above i t s n o r m a l
even s p a c i n g
were
moratality rates
their
of these
r a t e s at a l l i n t e r t i d a l
were w e l l below
Thus,
had h i g h e r
located
cannot l i v e
determined.
mortality
they
limit
greater
agonistic
The l o w e r
mean
a
maintain
behavior
intertidal
distance
to
i i i
nearest
that
neighbor
the
than
lower
d i d the
I
higher species.
s p e c i e s was
a superior competitor
If I f a i l e d to reject this hypothesis,
i t would
P-
t h e low
cinctipes
because
R-
of
unable
exclusion
eripmerus.
support
R'
is
Results
t h i s hypothesis
cinctipes
to
inhabit
by
agonistic
of
and
the
i n fact
consistently
were
tested
enclosures
that
intertidal
experiments
suggested
acquired
and
the
zone
with
did
not
contrary;
maintained
a favorable
i n t e r s p e c i f i c e f f e c t s on v e r t i c a l
a
habitat
in
that
P.
(runs).
By
eriomerus
comparing the d i s t r i b u t i o n s of t h e
preference
the
slightly
upwards.
experimental
zonation
of the run
I n c o n t r a s t , P. c i n c t i p e s
f o r v e r t i c a l range
mixed,
was
enclosures,
demonstrated a strong preference
p o r t i o n s of the runs.
that
P.
in
the
However, t h e r e
was
upper
range.
by b i o t i c
of i t s v e r t i c a l
from the p r e v a i l i n g
are
demonstrated
clear
When
shifted
indication
Results
reduced
p o p u l a t i o n near
This i s unusual
i d e a t h a t upper
the
in that
distributional
c a u s e d by p h y s i c a l f a c t o r s ( C o n n e l l 1972)
factors.
lower
P. c i n c t i p e s
P. e r i o m e r u s
limits
for
occurring w i t h i n the enclosures.
d e n s i t i e s of the e x p e r i m e n t a l
differs
found
population
no
two
I
enclosures.
cinctipes
e x p e r i m e n t s a l s o showed t h a t
limit
distribution
f o r i n an e x p e r i m e n t w h i c h e m p l o y e d l o n g , n a r r o w
species i n their single species control
it
suggest
arena.
I n t r a - and
no
f o r space.
interactions
arena
d i s p r o p o r t i o n a t e amount o f s p a c e o v e r
the
hypothesized
and
not
Other
cause
of
stresses
1972,
or
z o n a t i o n s t u d i e s have suggested t h a t
upper
from
1974).
v e r y slow
distribution
harsh
is
the
probably
of
density
also
The
lower
o f t h e P.
species
band.
space
£«
from
I
is
was
species
population.
were c o n d u c t e d on
sessile
cause
lower
In
contrast,
of
the
s p e c i e s t o an
limit
with
the
of
limit
higher
determine
remain
stresses
a
height.
n e a r i t s upper
population
physical
is
increasingly
intertidal
which
my
vertical
population
competition
below t h e l o w e r
unable to obtain
with the lower
cinctipes
that
lethal
1961b,
the f a c t o r ( s )
cinctipes
are
1961a,
population
by
of
unlikely
(Connell
with i n c r e a s i n g
of t h i s
nature
living
the
proximate
population
species.
the lower
lowered
species.
i t
for
environment
the
However,
studies
proximate
limitation
response
limit
environment
These
that
physical
However,
intertidal
moving i n v e r t e b r a t e
show
behavioral
o f an
the p h y s i c a l
Paine
results
limits
the
the
unresolved.
prevent
its
this
population
evidence that competition f o r
determined the lower
limit
of
the
TABLE OF CONTENTS
L I S T OF TABLES
. ...
L I S T OF FIGURES
viii
«
ix
ACKNOWLEDGEMENTS
xi
GENERAL INTRODUCTION
I.
FIELD
...
........i
OBSERVATIONS
,
7
Methods
7
The F i e l d
Survey
Sites
7
Methods
Vertical
7
Distributions
Transect
Patio
10
S u r v e y s ................................
Herring-roe
and M i l k - b a s k e t T r a p s
13
Predators
The O r g a n i s m s and t h e i r
14
Distributions
14
Zoogeography
Vertical
14
Distributions
Transect
...........
15
S u r v e y s ................................
16
Herring-roe
Vertical
10
11
Blocks
Intertidal
i n Barkley
and M i l k - b a s k e t
Distribution
Intertidal
Predators
Sound
T r a p s ..............
18
o f Megalopa and J u v e n i l e s
19
...........................
24
Discussion
II.
1
25
TRANSPLANT EXPERIMENTS
,
27
Introduction
27
Methods
27
Transplant
The
Cages
and E x p e r i m e n t a l A n i m a l s
1976 E x p e r i m e n t s
27
28
vi
The
1977 E x p e r i m e n t s
........
Developmental Stages
29
Results
30
Survival
of Transplanted
Embryonic
Survival
Development
Development
P. c i n c t i p e s
.
39
Introduction
39
...
40
The A r e n a and S e a w a t e r System
40
E x p e r i m e n t a l Animals and H o l d i n g
Data C o l l e c t i o n and S t a t i s t i c a l
Single
Procedure
A n a l y s e s ............
Species Experiments
Mixed S p e c i e s
43
44
46
Experiments
46
Behavioral Observations
47
Results
48
Single
Species
Experiments
48
Some B e h a v i o r a l O b s e r v a t i o n s
48
Interspecific
51
Differences
......................
Mixed S p e c i e s E x p e r i m e n t s
Discussion
IV.
35
37
EXPERIMENTS
Methods . . . .
33
. . . . . . . . . . . . . . 34
o f T r a n s p l a n t e d P. c i n c t i p e s
Discussion
ARENA
P. e r i o m e r u s . . . . . . . . . . . . . . 30
o f T r a n s p l a n t e d P. e r i o m e r u s
of Transplanted
Embryonic
III.
29
59
68
RUN EXPERIMENTS
............
70
Introduction
70
Materials
71
1976
and. Methods
E x p e r i m e n t s ...................................
72
vii
Run
Construction
Intertidal
Position
72
of the E n c l o s u r e s
72
Experimental Animals
73
i
Experimental Procedure
73
Counting
1977
..
74
E x p e r i m e n t s ...................................
74
Run
Construction
Intertidal
Position
74
of the Enclosures
74
Experimental Procedure
75
Counting
75
Statistical
Tidal
A n a l y s e s ................................
Experiments
R e s u l t s ......
Effects
Preference
Effects
Tidal
-.
on g. c i n c t i p e s
for Vertical
of Mixing
Preference
76
...
of Mixing
Location
-
80
....................
by P . . c i n c t i p e s
...
on P. e r i o m e r u s ...................
for Vertical
Location
by P. e r i o m e r u s ..
Experiments........
and
85
86
91
95
DISCUSSION
Density
80
91
Discussion
GENERAL
75
97
Vertical
Distribution
of the
P. e r i o m e r u s
Population
The Lower L i m i t
REFERENCES CITED
97
o f t h e P. c i n c t i p e s
Population
.......
103
105
viii
L I S T OF TABLES
Table
I. R e s u l t s o f the t r a n s e c t
Table
II.
Number
o f c r a b s which
surveys
17
entered
the h e r r i n g - r o e
traps. .
Table
18
I I I . Developmental stages
transplanted
Table IV.
stages
of
by
embryos
carried
by
P. c i n c t i p e s . .
neighbor
36
V. N e a r e s t
Table
VI. Nearest
neighbor
Table
V I I . Forced
and p a s s i v e e x i t s
the
carried
33
Table
during
embryos
P. e r i o m e r u s .
Developmental
transplanted
of
first
s t a t i s t i c s f o r P. c i n c t i p e s . . . .
49
s t a t i s t i c s f o r P. e r i o m e r u s . . .
50
from
under t h e
hour o f i n t r a s p e c i f i c arena
block
exper-
iments....
66
Table
V I I I . Observed
Table
I X . Mean
respective
Table
k v a l u e s and t h e i r
percentages
test
X. Some t i d a l
of
and c o n t r o l
statistics
each
ratios...
species
in
67
their
r u n s . . . . . . . . . . . . . . . . . . . . . . . 85
94
ix
L I S T OF
Figure
1.
Map
Figure
2.
Size
FIGURES
of southeastern
class
Barkley
Sound.,
distributions
of
the
8
1975
trap
entries...............
Figure
the
3.
20
Number o f c r a b s
patio
less
t h a n 2.0
mm
found
under
blocks......................
Figure
4.
Survival
rates of.transplanted
Figure
5.
The
Figure
6.
Distance
Figure
7.
Distances
22
Petrolisthes...
arena...
41
to nearest
moved by
neighbor.............
crabs
during
52
intraspecific
encounters.
54
Figure
8.
Effects
Figure
9.
Fight rates
Figure
10.
Mixed s p e c i e s
Figure
11.
Large
of i n i t i a l
vs.
density
on
k....,
.....57
60
arena
small
experiments...............
crabs
in
mixed
Figure
12.
Diagram
Figure
13.
Vertical
Figure
runs i n
Figure
64
o f one
of
the
distribution
tanks...
o f P.
cinctipes
78
in
the
15.
Vertical
81
distribution
16.
of
P.
cinctipes
in
the
1977...
Vertical
83
distribution
r u n s i n 1976..
Figure
tidal
i n 1976
14.
Vertical
r u n s i n 1977
62
species
encounters.
runs
31
of
P.
eriomerus i n
the
...............
distribution
of
P.
eriomerus
87
in
the
89
X
F i g u r e 17-.Crabs i n the
Figure
18.
traps
Summary
and
of
runs....
upper h a l f
of the t i d a l
the d i s t r i b u t i o n s
tank.,-..
92
of c r a b s i n t h e
98
ACKNOWLEDGEMENTS
I wish t o thank
my
advisor,
Dr* P.A. D e h n e l
for his
advice,
support
and e n c o u r a g e m e n t d u r i n g t h e c o u r s e o f t h i s
s t u d y . My c o m m i t t e e members, D r s . T.H. C a r e f o o t , R.E. Foreman,
W.S. H o a r , C . J . K r e b s a n d G.G.E. S c u d d e r o f f e r e d many v a l u a b l e
comments.
Many p e o p l e f r o m t h e town o f B a m f i e l d , B r i t i s h
Columbia,
gave
assistance
and companionship.
J o h n Boom, Wendy C r a i k ,
D o m i n i q u e G a s c o n , C l i f f H a y l o c k , Myriam H a y l o c k a n d Tom Herman
gave h e l p and a d v i c e above and beyond t h e c a l l
o f duty.
I
also
w i s h t o t h a n k Dr. John M c l n e r n y who p r o v i d e d h o u s i n g a n d
shop
facilities
at the Bamfield
Marine
Station.
Geoff
Lindsey
and Rob S a u n d e r s of C a n a d i a n B e n t h i c L t d . g e n e r o u s l y
made a v a i l a b l e f l o o r s p a c e i n t h e i r d e l u x l a b o r a t o r y
complex.
Canadian
Packers
L t d .provided
their
stately
mansion i n
B a m f i e l d s o t h a t many o f us h a d a p l a c e
to live
during the
summer
o f 1975.
Tidal
strip
chart
recordings
from t h e
B a m f i e l d t i d e gauge s t a t i o n were o b t a i n e d from
the Institute
of Ocean S c i e n c e s , Sydney, B r i t i s h C o l u m b i a .
The
U n i v e r s i t y o f B r i t i s h C o l u m b i a Computer C e n t e r s t a f f
were most h e l p f u l d u r i n g t h e c o u r s e
of the data
analysis.
T h e i r c o n s i d e r a t e s e r v i c e and p r o f e s s i o n a l a d v i c e s h o u l d s t a n d
as
a shining
example
f o r any campus
organization
which
p r o v i d e s s e r v i c e s t o s t u d e n t s and r e s e a r c h e r s .
The s t a f f
of
the
B i o l o g y D a t a C e n t e r were a l s o e x t r e m e l y h e l p f u l .
I will
a l w a y s be g r a t e f u l t o B i l l
Webb
f o r giving
me
help
with
v a r i o u s computer programming p r o b l e m s .
Most
importantly
my
warmest
thanks
t o my w i f e F l o y .
Without her help i n the f i e l d
and h e r encouragement,
this
study
would
n o t have
been
possible.
I am
a l s o deeply
g r a t e f u l f o r t h e time she spent drawing t h e f i g u r e s
f o r this
thesis.
the
T h i s r e s e a r c h was s u p p o r t e d by a g r a n t t o D r . D e h n e l
N a t i o n a l Research C o u n c i l o f Canada.
from
1
GENERAL
One o f t h e more a b r u p t
the
interface
between
Within
t h e rocky
often
demonstrate
term
zonation
INTRODUCTION
e c o l o g i c a l t r a n s i t i o n s on e a r t h
aquatic
intertidal
or
environment,
clearly
banding
demarcated
has
conspicuous
distributions
populations.
A considerable
patterns
has
Southward
and t e r r e s t r i a l
been
of
vertical
to
populations
ranges.
(for
these
and
describing
reviews
The
describe
invertebrate
literature
accumulated
environments.
benthic
used
is
see
plant
zonation
Doty 1957,
1958, L e w i s 1964, R i c k e t t s and C a l v i n 1968,
Hedgpeth
1976) .
Many
attempts
zonation
patterns.
various
tidal
explain
have
Some r e s e a r c h e r s
phenomena,
zonation
but,
reviews
see
1977) .
Because steep
the
show
Doty
intertidal
that
individual
intertidal
relative
(Foster
studies
such
have
gradients
to
organisms l i m i t
been
and
to species
which
(for
1976, C a r e f o o t
have
over
attempted
to
d e m o n s t r a t e d by
distributions
laboratory
frequently
demonstrate
of i n t e r t i d a l
determined
that
higher
tolerances to physical stresses
i n h a b i t lower
1969,1971a,1971b,
use
levels, to
unsuccessful
stresses
between
s p e c i e s have g r e a t e r
to
i n p h y s i c a l f a c t o r s occur
vertical
zonation
tide
1972, Hedgpeth
physical
Relationships
attempted
critical
largely
1957, C o n n e l l
tolerances
provide
as
have
zone, s e v e r a l i n v e s t i g a t o r s
populations.
tolerances
been made t o d e t e r m i n e t h e c a u s e s o f
Wolcott
contrasts i n relative
p o s i t i o n s on t h e
1973).
Although
adaptation,
they
shore
these
cannot
2
in
themselves
explain
reason f o r t h i s
are
compared
what
i s that
with
when l a b o r a t o r y
physical
these tolerances
o f t e n exceed
1973).
lower
Also,
physiologically
organisms
when
(Connell
able
demonstrate
1972).
to live,
observed
1953,
to
increased
limits
of
interactive)
niches.
within
the
ranges
species
can l i v e
Vandermeer
by
of
growth
submergence
when t r a n s p l a n t e d , a r e
intertidal
population
1974).
levels
below
( B a r n e s and P o w e l l
Apparently
distributions.
provoked
much t h o u g h t
of the
slower
mechanisms
environments
Hutchinson's
several
An i m p o r t a n t i d e a
of
the
why do s p e c i e s
and r e a l i z e d
fundamental
(post-
niche
lies
a l l e n v i r o n m e n t a l g r a d i e n t s i n which
and r e p r o d u c e
occurred.
fundamental
and
The
niche
before
realized
to
which
competitive interactions
1972, C o n n e l l
and
p r e s e n t e d i n h i s model
(preinteractive)
Briefly,
(1958)
investigations
concerning the question:
o f t h e fundamental
constrained
the
or
and b i o t i c
o c c u r where t h e y do?
portion
intertidal
from b o t h t h e p h y s i c a l
has
has
Some
1968). .
niche
competitors
represent
(denHartog
species'
concept
always
periods
at
(Wolcott
factors are involved
seem t o d e t e r m i n e
that
high
1961b,1972, P a i n e
Constraints
is
not
mortalities
abnormally
tolerances
conditions
limitations.
grow and r e p r o d u c e
other than a b i o t i c
stimulated
field
do
One
encountered i n nature,
However, many s p e c i e s ,
lower
Connell
extreme
zonation.
determined
stresses
limits
imposed
subjected
causes i n t e r t i d a l
1975, H u t c h i n s o n
interactions
a
with
niche i s a smaller
the
species
i s
( c o n c e p t s r e v i e w e d by
1978)..
In
addition
3
to
competition,
interaction
predation
can
which c o n s t r a i n s
fundamental niches
Some o f
the
Hutchinson's
(Paine
be
species
1974,
concept
to
a
Connell
most c o n v i n c i n g
niche
another
portion
f o r the
a model e x p l a i n i n g p a t t e r n s
in
rocky
intertidal
Connell
conducted
(1961a,b,
(1974) h a v e shown t h a t i n t e r t i d a l
species l i v e
ranges
smaller
are
physiologically
others
capable
(reviewed
limits
occur
at
t o l e r a n c e t o an
of
barnacles
portion
warm
Hodgkin
1960,
Foster
trophic
After
Connell'
1972)
the
extremes
of
limpets
by
balanpides,
population
environment.
these
a
within
those
These
species'
the
Paine
vertical
they
studies
and
physiological
environment.
1973).
study
not
of
Species
upper
live
in
against
one
within
of the
concluded
the
other
(Lewis
seem
or
with
long
1954,
Sutherland
predation,
populations
(1970)
unusually
limits
either
and
I n t e r a c t i o n with
population
1965,
Lower
interactions
to
stresses
Frank
(competition
Connell
animals
are
upper
m o r t a l i t i e s at the
desiccation
1961a,
Wolcott
biotic
does
and
have s u g g e s t e d t h a t
demonstrated
and
Connell
levels
in
r a n g e s a t t i m e s when neap t i d e s c o i n c i d e d
thermal
a thorough
adult
by
1970)
than
inhabiting.
subjecting
1971a,
determined
the
and
weather,
of
of
increasingly terrestrial
of t h e i r
periods
considerably
their
of
comes f r o m e c o l o g i c a l i n v e s t i g a t i o n s
which
of
usefulness
nature
zone.
biotic
1975) .
evidence
as
important
1970,
to
be
between
respectively).
barnacle
Balanus
"...the
breeding
that
optimum
physiological
species...in effect
push
margin o f i t s h a b i t a t , f o r c i n g
4
it
to l i v e
i n less
Unlike
adjust
barnacles
their
Upper
ultimately
set
physiological conditions.
and m u s s e l s ,
vertical
stresses.
vertical
favorable
species
of
some
physical
p o s i t i o n s of these
gastropod
factors.
limits
In
some
shore
in
t o s t r e s s e s which
summer months, r e t u r n i n g t o t h e s e
weather
inhabitable
1976).
of
and i n c r e a s e d
(Lewis
Branch
seasonal
to
alleviating
ranges
which
favorable
Hayes
that
shore
physical
1926,
Bock
motile
conditions
not
are
i t
alter
Johnson
favorable
during
the
or
maintain
dry
when
regions
1975,
importance
allows
foraging
these
ranges,
basis.
maintain
both
1967).
for
winter
on a t e m p o r a l
the
hot,
Branch
probably
their
Some
on
made t h e s e
either favorable
conditions
and
levels
1972,
spj>.) a p p a r e n t l y
and m u s s e l s , p e r i w i n k l e s
vertical
food
sources,
(Gowanloch
and
These s t u d i e s i n d i c a t e
vertical
their
adjust
p o s i t i o n s on t h e
survival.
their
Unlike
upper l i m i t s
as
warrant.
Factors
are
that
them w i t h
species actively
which
barnacles
present
cases, the
that the adaptive
competition
(Littorina
in
1965, B r e e n
periodically
intraspecific
Periwinkles
levels
(1975) s u g g e s t e d
is
occurred
wave a c t i v i t y
1954, F r a n k
migration
populations
to
are
fluctuate seasonally.
s p e c i e s h a v e been shown t o move f r o m h i g h
cooler
able
populations
limpet
response
are
p o s i t i o n s i n response t o p h y s i o l o g i c a l
limits
by
motile
1 1
which i n f l u e n c e t h e l o w e r
w e l l known.
Periwinkles
limits
of m o t i l e
and some l i m p e t s
species
migrate to
5
higher
they
p o s i t i o n s when a r t i f i c i a l l y
normally
Castenholtz
occur
1961,
Bock and
Populations
Petrolisthes
observed
zone
The
of
limit
these
porcelain
Wicksten
slightly
Both
crabs,
1973,
by
a
This
and
The
was
limit
of t h e
reviews
acquire
P.
of t h e
the
conducted
their
the
and
P.
its
survive
section
observed
lower
than
i s concerned
filter
intertidal
feeding
similar
The
literature
for
like
other
(Nicol
1932,
barnacles
purpose of
this
interspecific
had
and
on
setting
the
limit
observed
of
The
these
distributions
intertidal
with
eriomerus
to
roles
a
upper
population.
vertical
its
Columbia.
P.
and,
composed o f f o u r p a r t s .
upper
were
demonstrated
of the
cinctipes- population
crabs,
Stimpson
the
habitat preference
e x p e r i m e n t s t o d e t e r m i n e whether P.
than
in
cinctipes,
what
1954,
1972)..
eriomerus
ranges
which
North
porcelain
basket).
section presents r e s u l t s
in
P.
manner
determine
zoogeographical
describes
second
is
by
in a
eriomerus
thesis
of
highly motile
filtering
to
Connell
upper l i m i t
food
1975)
interactions
lower
limit
s p e c i e s , P.
species are
Caine
1926,
below
of Vancouver I s l a n d , B r i t i s h
below t h e
setose
investigation
agonistic
two
1967,
and
vertical
at l e v e l s
Hayes
species
(Randall)
west c o a s t
population.
the
two
cinctipes
the
higher
(i.e.,
of
and
Johnson
t o have d i f f e r e n t
on
lower
(Gowanloch
placed
I
whether P*
lower
l a b o r a t o r y arena
limit.
part
species
Sound.
experiments
conducted
e r i o m e r u s - can
and
two
i n Barkley
transplant
zone.
first
live
these
higher
cinctijoes
The
can
third
e x p e r i m e n t s which
I
6
conducted t o determine whether b e h a v i o r a l
between
these
two
species.
Specifically,
whether t h e r e
were a n y
requirements
and w h e t h e r i n t e r s p e c i f i c
if
present,
preferred
field
interspecific
habitat.
the
upper l i m i t
role,
species
in
which
agonistic interactions,
conducted
by i t s r e s p e c t i v e
i f any, p r e f e r e n c e
h a d on t h e s e
I
spatial
from
limits.
a
r e s u l t s from
to
determine
o f P. e r i o m e r u s o r t h e . l o w e r l i m i t
P« c i n c t i p e s were i n f l u e n c e d
what
differences
The f o u r t h s e c t i o n p r e s e n t s
experiments
existed
I w i s h e d t o know
w o u l d l e a d t o t h e e x c l u s i o n o f one s p e c i e s
enclosure
whether
differences
congenitor
of
and
f o r v e r t i c a l l o c a t i o n by e i t h e r
7
I.
FIELD
OBSERVATIONS
Methods
The
Field
All
site
a
Sites
field
(Fig. 1).
boulder
both
This
field
Diana I s l a n d
of
experiments
site
site
was a g e n t l y
was c h o s e n
s p e c i e s , i t was
populations
because
protected
were
The f i r s t
p o p u l a t i o n s o f both s p e c i e s .
made
at
Islets
the
Taylor
sites
had
Islet
intertidal
c o n t i n u o u s t o a depth of about
and
Taylor
during
Islet
received
had
The
populations
and
Observations
Island,
Diana
Ross
sites
Only s u b t i d a l
site.
which
wave a c t i v i t y
sites:
four
Island
( 0 . 0 m).
dense
f r o m heavy
Haines
Diana
beach
datum
i t had
made a t f i v e
(Fig.1).
Islet
sloping
most o f t h e y e a r .
Dodger C h a n n e l , G r a p p l e r I n l e t ,
Taylor
at the
e x t e n d i n g down t o a b o u t
was a c c e s s i b l e t h r o u g h o u t
natural
were c o n d u c t e d
Island i n
Islets
had
and
intertidal
observations
The H a i n e s
of
Island
were
and Ross
boulder
beaches
which
were
5 m below
datum.
Haines
Island
considerable
storms, while the other s i t e s
pounding
were w e l l
from
waves
protected.
S u r v e y Methods
Vertical
and
a
nearest
h e i g h t s were d e t e r m i n e d
with a
r o d t o t h e n e a r e s t 0 . 0 1 f t and w i l l
0.1
m.
Datum
is
that
adopted
surveyor's
level
be e x p r e s s e d t o t h e
by
the
Canadian
3
Figure
1. Map
Island
of southeastern
site;
floatshed;
D,
Barkley
Sound. A, t h e
B, t h e G r a p p l e r I n l e t
boulder
beach n e a r
site;
Cape
C, t h e
Beale.
Diana
9
10
Hydrographic
S e r v i c e : the
Vertical
p o s i t i o n s were
cemented
i n t o bedrock.
a staff
gauge at
plane
of
measured
The
Bamfield,
the
lowest
relative
bench
British
to
mark was
Columbia
normal
a
tides,.
bench
mark
calibrated against
( F i g . 1).
Vertical Distributions
Vertical
distributions
Petrolisthes
were d e t e r m i n e d
were: t r a n s e c t s u r v e y s ,
milk-basket
Transect
to
Island
Transects
that
traps)
cement
vertical
site
during
at
populations
methods.
of
patio
traps
of
These methods
(herring-roe
and
blocks.
least
low
two
sand
along
the
lowest
P.
vertical
p o s i t i o n s of these
12
and
a high
aid
This
transect
surveys
markers,
which
did
the
were
and
length
not
was
of
the
P.
painted
the
of
the
so
transect
distributions.
of
the
eriomerus.
bench
The
mark
series
were
limits
with
the
same methods as
above e x c e p t
white,
I) .
were s e l e c t e d
p o s i t i o n s of these
done u s i n g
the
Table
over i n search
a neap t i d e
described
in
limit
highest
1977
tide
which are
(dates
i n d i v i d u a l s below
September
were marked d u r i n g
SCUBA.
over the
t r a n s e c t were t u r n e d
cinctipes
On
tides
meters apart
barriers
Boulders
measured.
t r a n s e c t s were e s t a b l i s h e d a t
were c o n t i g u o u s
i.e.,
of
three
types
eight
were
boulders
line,
and
two
by
natural
Surveys
Five
Diana
of
were p l a c e d
that
at the
the
cement
upper
11
limit
o f P. e r i o m e r u s
placed
at
the
a n d m a r k e r s which were p a i n t e d
lower
p o s i t i o n s o f these
water o f t h e next
limit
of
P. c i n c t i p e s .
m a r k e r s were d e t e r m i n e d
spring
tide
red
were
The v e r t i c a l
d u r i n g t h e l o w e r low
series.
H e r r i n g - r o e a n d M i l k - b a s k e t Trap_s-
In o r d e r t o d e t e r m i n e
(<5.0
mm
baskets
These
(Columbia
baskets
initial
In
maximum
baskets
by
crabs
enter
relative
carapace
than
Size
to
width
ends.
end
sides
up
were
in
stage).
crabs i n the
14 mm.
this
the
size
abundance
classes,
measured
I
later
be made
could
with
of
not
smaller
occurred over t h e
3.0 mm
max-
a millimeter
rule.
w i t h an o c u l a r
micrometer
t o t h e n e a r e s t 0.04
flared
44 x 31 cm
used.
f r e q u e n c i e s were compared t o
mm.
outward t o w a r d s t h e i r
The i n s i d e b o t t o m d i m e n s i o n s
dimensions
to
than
3.0 mm were measured
of the baskets
were
e n t r i e s could e a s i l y
class
microscope
herring-roe
larval
equal t o or g r e a t e r than
were
mounted i n a d i s s e c t i n g
The
(the post
a l l other s i z e
Crabs
juveniles
l e v e l s i n May 1975 w i t h an
of
that
differences
levels.
Those l e s s
widths
Crabs l a r g e r
traps.
B.C.)
by s m a l l c r a b s , I f o u n d
i n the laboratory
whether
trap
imum
carapace
perforated
L t d . , Vancouver,
entries
o f <13 mm.
determine
four
to
these
crabs,
Plastics
positions of
width),
o f t r a p p i n g megalopa
with
determined
carapace
were s e t o u t a t f o u r
intent
addition
the v e r t i c a l
and
open
were 41 x 28 cm, t h e open
the
depth
was
9.5 cm.
12
Baskets
were
intertidal
enclosed
filled
zone
by
at
with
the
lashing
rocks
Diana
plastic
Island
four different
measured
from
selected
on t h e
(no
P.
vertical
t h e bottom
eriomerus)
observed
only).
and
m
at
a t each
October
1975
plastic
by
quickly
garbage
the
adult
datum
bag.
bags
In t h e
and
i n May
were
(the upper
one
were
+0.3
0. 6 m above
limit
of
present
were
were r e t r i e v e d
one
into
m
datum
meter a p a r t ,
Baskets
each
1975
heights
(P. c i n c t i p e s
approximately
were
These h e i g h t s
level),
the
They
distributions:
m above datum
placing
in
open e n d s .
Island site
basket.
of the f o u r l e v e l s .
high
Baskets
Vertical
this
above
Three r e p l i c a t e s ,
placed
from
1.2
Diana
o f each
( b o t h s p e c i e s p r e s e n t ) , 0.9
P.
site.
levels.
b a s i s of adjacent
cinct ipes
from
screen to t h e i r
were p l a c e d among b o u l d e r s a t t h e
at
collected
a
in
separate
l a b o r a t o r y , c r a b s were removed
preserved
for
later
counting
and
identification.
On
site,
4 May
using
baskets.
all
size
width
of the
shaped h o l e s .
both
x 31
site
mm.
with
milk-baskets
baskets
classes.
dimensions
along
t r a p s were a g a i n
plastic
These
t h e bottom
54
1977
The
of
baskets
axes,
on
those
I have n o t
carapace
and
instead
openings
milk-basket
33 cm
Holes
had
placed at the
cm
were'perforated
the
on
bottom
the
observed
widths
had
had
with
greater
than
The
of
lengthsides
and
s e v e r a l diamond-
axial
the
20
entry
equal
dimensions
at
Island
herring-roe
high.
s i d e s had
crabs
of
which a l l o w e d
traps
were 24
Diana
of
24
mm
dimensions
of
Diana
mm,
Island
making
i t
13
unlikely
that hole
class.
1975
Rocks
traps.
basket
size
were
limited
e n t r i e s by
collected
i n the
C r a b s were removed by
trap
into
a
large
R o c k s were removed s i n g l y
presence
of
Petrolisthes,
some s e a w a t e r .
Species
the
the
and
in
basket
returned to i t s
original
traps
were
Diana
t h e same
laboratory.
s e t a t the
vertical
replicates
The
(three
per
were t o be e x a m i n e d on
levels
were
inclusive.
This
attempt
Following
several
l o s s e s from
data
collected
which a r e
Patio
the
complete except
with
recorded
The
early
the
i n July
same
every
low
tide
in
1977
serial
and
f o r the
loss
o f one
traps.
13 O c t o b e r
1977
was
not
there
were
have
trap observation
of
all
observation
I
at
which
sampling
unknown c a u s e s .
1977
number
basket
June
the
milk-basket
1975
second
first
were
used
(29 J u l y
the
1977)
basket.
Blocks
The
third
to determine
widths
30.5
from
the
a j a r with
the
at
the
for
as
between 29
successful.
basket
position.
level)
escapes.
examined
widths
milk-
r o c k s were r e p l a c e d and
and
Baskets
exposed
and
Island site
positions
size
a
to catch
were p l a c e d i n t o
carapace
later
any
placing
dishpan
basket
which
of
same manner a s f o r t h e
quickly
plastic
from
crabs
of
x 30.5
vertical
method e m p l o y e d cement p a t i o b l o c k s and
vertical
<2.0
x 5.1
mm.
cm.
distributions
The
Blocks
l e v e l s at the Diana
of
juveniles
dimension
were p l a c e d
I s l a n d and
of
at
Grappler
with
a
was
used
carapace
block
four
Inlet
was
different
sites
in
14
August
1974.
These l e v e l s
herring-roe
and m i l k - b a s k e t
replicates
about
examined
spring
to
a r e t h e same as t h o s e
t r a p s were s e t .
series
5 October
on t h e i r
(approximately
1975.
undersurfaces
monthly) f r o m
Carapace
widths
present
t o determine
in
the
s p e c i e s was b r o u g h t
aquarium.
After
porcelain
into
crabs
the
placing
Blocks
were
during
each
16 August
1974
an
microscope..
Predators
I attempted
were
three
were measured w i t h
o c u l a r m i c r o m e t e r mounted on a d i s s e c t i n g
Intertidal
T h e r e were
one meter a p a r t a t e a c h l e v e l .
f o r small juveniles
tide
a t which t h e
crabs
the
three
(>10 mm
under
chiton Placiphorella
The
intertidal
to
aquarium.
whether p o r c e l a i n
zone.
five
and
days
the
one
case
anterior
placed
two
maximum c a r a p a c e
In
predators
A suspected
laboratory
to
crab
or
width)
encounters
girdle
of
predator
into
an
three adult
were
dropped
were s t a g e d
the
by
predacious
yellata.
O r g a n i s m s and t h e i r
Distributions -
Zoogeography
Based
Abele
on
geographical
1976) i t i s r e a s o n a b l e
underwent
tropical
the
seas.
major
distribution
to
assume
part of their
Petrolisthes
(Haig
that
1960, Gore and
porcelain
crabs
evolutionary divergence i n
cinctipes
and
P. e r i o m e r u s
are,
15
however,
abundant
Pacific
i n cooler
Ocean.
distributions,
Alaska
Both
namely,
( H a i g 1960,
vertical
are
filter-feeding
In
addition
abundant
(Hewatt
Vertical
(Haig
Haines
the
low
under
Calvin
southern
different
zone.
Both s p e c i e s
l i v e - under
b o u l d e r s , P.
threads
t o about
demonstrate
i n the i n t e r t i d a l
byssal
of
boulders.
cinctipes i s also
Mytilus
californianus
1968).
c i n c t i p e s i s almost e x c l u s i v e l y
1960).
Island
over a
below
datum
population
zone.
4 yr period,
tide
was
P. c i n c t i p e s ,
A t the
datum)
actual
lower
occasionally
Sebastes
as
limit
o f P.
found
this
which
datum.
an
adult,
several
unable
upper
intertidal
was
of
at a l l s i t e s
nebulosus
below
The
eriomerus,
down t o t h e maximum d e p t h
below
I was
and
an
the
the e a s t e r n shore
dives
to find
at
eriomerus
boulder
In
contrast
under
fields
even
s p e c i e s i n t h e gut
at
nebulosus
occurs
five
l i m i t o f t h e P.
e r i o m e r u s - m a y be
rarely
the
in
cinctipes
commonly f o u n d
were c a u g h t
limit
P.
zone.
any
except the Diana I s l a n d
Sebastes
intertidal
c i n c t i p e s - h a s i t s lower
During
level.
i n t h e low
P.
Ross I s l e t s
( F i g . . 1) , P.
intertidal
sites
which
but
latitudinal
D i s t r i b u t i o n s i n Barkley-Sound -
of
10 m
California
R i c k e t t s and
Petrolisthes
species
southern
196 8 ) ,
similar
anomuran c r a b s w h i c h
among t h e
of the northeastern
have
to occurring
1935,
waters
species
Hart
distributions
marine
in
to
boulders
(about
5 m
site.
The
lower.
I
have
contents of
adult
depths
greater
i s a demersal
intertidal
than
fish,
regions
16
( p e r s o n a l communication
£•
t r a n s e c t survey
positions
o f the upper
limit
of
little
change.
( T a b l e I)
(i.e.
any
data
limit
P. c i n c t i p e s
suggest
highest
of
the
1977
was
represents
the
Therefore,
i t
cinctipes
searched
at
population
the high
the
at
for
2.4 m
that
was c a u s e d
the
horizontally
was
observed
above
limit
o f P. e r i o m e r u s change l i t t l e ,
other
in
upper
datum.
limit
above
On
of
the
The h i g h e s t
datum
which
also
this
site.
boulders
at
upper
limit
of
(Table I) e s t i m a t e d
water o f a neap t i d e s e r i e s and
three
means
the
by h a b i t a t d i s c o n t i n u i t y .
limit
1977, I n o t e d
the
1977 t r a n s e c t s
lower
summer
0,6 m
the
neither
Also, during
varied l i t t l e
of
that
tide.
errors of
was 0.9 m above datum, and t h e
limit
likely
lower
demonstrated
a t t h e Diana I s l a n d s i t e .
upper
12 September
during
found
found
is
the
edge).
surveys
was
I
limits
and
site
a t which P. e r i o m e r u s
population
P. c i n c t i p e s
limits
level
transect
cinctipes
the Diana I s l a n d
t h a t these
P. c i n c t i p e s
August
P. e r i o m e r u s
Also, the small standard
The
The
1960).
( T a b l e I) show t h a t t h e v e r t i c a l
of
at
p a r a l l e l t o water's
lowest
a t -86 m (Haig
In C a l i f o r n i a ,
Surveys
The
£-
N.J. W i l i m o v s k y ) . .
e r i o m e r u s h a s been o b s e r v e d
Transect
29
from
o f P. c i n c t i p e s
i f
dives
at
a l l , during
limits
suggest
nor t h e upper
made a t h i g h
p o s i t i o n s of these
these
high
tide
during
relative
to the
17
Table I . Results of the t r a n s e c t . s u r v e y s .
Means and s t a n d a r d e r r o r s a r e i n m e t e r s above
datum.
Lower L i m i t
of
P. c i n c t i p e s
n
mean
7
0. 7
0.04
0.8
0.04
1975
10
8
6
0. 6
0. 7
0. 6
0.07
0.06
0.04
0.7
0.8
0.8
0.06
0.04
0.07
1 1 J u n e 1976
25 Aug
25 S e p t
6
8
7
0. 6
0. 6
0. 6
0.05
0.04
0.06
0.8
0.8
0.03
0.03
16
29
12
6
5
7
0. 6
0. 6
0. 7
0.03
0.03
0.05
0.8
0. 8
0. 7
0.03
0.04
0.03
16
Oct
1974
10 J u l y
4 Nov
3 Dec
June
Aug
Sept
1977
cement p a t i o b l o c k s
rocks
in
Upper L i m i t
of
P. e r i o m e r u s
and p l a s t i c
se
markers
I
a t +0.3, +0.6 and +0.9 m.
the
location
of
the
mean
lower
which
limit
of
f r o m +0.6 m o r t h e upper l i m i t
+0.9 m.
This
l i m i t s a r e t h e same d u r i n g
exposure.
my
earlier
periods
were
wired
to
d i d not observe d i f f e r e n c e s
population
supports
se
of
the
P.
cinctipes
o f P. e r i o m e r u s -
observation
tidal
that
submergence
from
these
and
18
Herring-roe
Data
transect
and M i l k - b a s k e t
presented
survey
in
data
Traps
T a b l e s I I and I I I f u r t h e r
( T a b l e I)
in
that
support
there
were
the
no
T a b l e I I . Number o f c r a b e n t r i e s i n t o t h e h e r r i n g r o e b a s k e t t r a p s i n 1975 and i n t o t h e m i l k - b a s k e t
t r a p s i n 1977.
P. c i n c t i p e s
replicate : 1
2
1975
1.2 m
0.9
0.6
0.3
393
366
89
24
4 16
2 52
250
• 0
1977
1.2 m
0.9
0.6
0.3
26
34
2
0
12
4
2
0
P- e r i o m e r u s
entries
none a t t h e +0.9
were
43
at
m level
P. e r i o m e r u s
the
i n 1975
entries
P.
3
n. a.
267
249
0
1.2
at
the
1977,
only
level
0
0
79
172
0
0
48
226
(Table I I ) .
t h e r e were no P. c i n c t i p e s
this
2
'
3
n. a.
0
166
290
0
25
18
14
0
11
n. a.
19
m levels i n either
Conversely,
and
1
0
7
7
35
23
15
n. a.
0
eriomerus
y e a r and
However,
+0.9
m level
entries
at
there
i n 1977.
+0.3 ra i n
24 i n d i v i d u a l s had e n t e r e d one o f t h e t r a p s a t
i n 1975
( T a b l e II) .
This suggests
that
the
lower
19
limit
of
P.
that
there
c i n c t i p e s was
is
limit
Vertical
of
P.
M e g a l o p a and
to.
proportions
each
that
of
level
the
to the
m and
those
of
crabs
<5.0
vertical
s u r v i v a l of
0.47
at
+1.2
four
P.
cinctipes
0.54
at
II).
+0.9
(n=68).
large
late
patio
block
also
small
juveniles
( F i g . 2).
levels
at
(<5.0
at
proportion
of
high
m,
the
at
those of
mm)
0.43
entries
a t +0.3
at
at
+0.6
P.
+0.6
m
but
clearly
populations
( F i g . 3).
which p o p u l a t i o n s
(n=25) and
This
of
mm
conspecifics
were
There
were
at
+0.3
juveniles
0.76
at
+0.3
m
juveniles
during
supported
by
were f o u n d
only
occurred.
m
were
constitute
both s p e c i e s
i s also
the
1977
eriomerus
juveniles
C r a b s <2.0
of
P.
of
proportion
in
none
eriomerus
of
favorable
The
(n=53) .
and
at
suggests
Results
1975.
m
m
of
are
each l e v e l
+0.9
proportions
e a r l y autumn.
data
were s i m i l a r
adults
(n=61), and
proportion
relative
by
(n=43) , 0,36
summer and
of e i t h e r s p e c i e s
The
inhabited
Relatively
were o b s e r v e d
adults.
ranges
The
m
vertical distributions
which
cinctipes juveniles
the
Juveniles
conspecific
were s i m i l a r t o
species
m above datum.
occurred),
of
(Table
+0.9
conspecifics
trap
m
around
least
that
which
1977
P.
m above datum) , and
Megalopa-and
mm
(or a t
abundance o f t h i s
j u v e n i l e s demonstrated
(at
sets
+0.3
e r i o m e r u s was
D i s t r i b u t i o n of
similar
m above datum
a sharp break i n the
somewhere between +0.6
upper
a b o u t +0.6
a
the
the
at
20
Figure
2. S i z e
There
d i s t r i b u t i o n s o f t h e 1975 t r a p
were no P. e r i o m e r u s
levels.
in
class
entries
The number o f e n t r i e s
T a b l e 2.
into
entries.
a t t h e 0.9 and 1.2 m
each
basket
a r e shown
P. cinctipes
Carapace Width
P. eriomerus
(mm)
ure
3. Number o f c r a b s l e s s
patio
blocks.
ranges. C i r c l e s
site
2.0 mm
found under t h
The c u r v e s are. drawn t h r o u g h
three r e p l i c a t e s
P. e r i o m e r u s ;
than
at each
level. Vertical
a r e f o r P. c i n c t i p e s ;
closed
and open s y m b o l s
t h e mean o
l i n e s are
triangles,
symbols a r e f o r t h e Diana
for the Grappler Inlet
Island
site.
23
20
I
I
8
1.2 m /t
4r
co
_ct>
0
I
1 CrJ
l-A-L-Oji-Q-d-A-
"-O-J-
C
1
0.9 m
>
~)
«+—
o
L.
(D
8
0'
0.6 m
L—A-l
i-M-^-do-m-d—^— A
L
1
0.3 m
0
LO-*1-
A
S O N.D J
1974
F
M A M J
J A
1975
0
1
S
_J#.
1
O N
24
Intertidal
Predators
I was
effective
£*
unable
to find
p o p u l a t i o n band
Rhacqchilus
vacca)
high t i d e .
However, t h e
prevented
i t
was
from
often
from
Petrolisthes.
but
predator
enough t o e x p l a i n t h e w e l l
cinctipes
sculpin
a
individuals
large
species
adults of either
Petrolisthes
consumed
amphipods
beaches
near
P.
cinctipes
I
found
site
Trinidad,
at the
chiton,
P.
However, d e n s i t i e s
very
low
Therefore,
£-
cinctipes
survival
low
will
kill
seems
r a t e s o f P.
intertidal
not
of
inhabited
and
chiton
observe
at the
were
mussel.
inhabiting
areas
zone.
to eat
readily
On
boulder
which
do
Diana
the
closer
species.
site
than
vellata
below
+0.6
not r e s t r i c t
were
2m).
prevents
m..
were t r a n s p l a n t e d
II) , suggest
Island
carnivorous
Diana I s l a n d
P.
of
octopods.
Petrolisthes
rarely
that
microbes
large
they
occurred at the
unlikely
and
tide,
I have o b s e r v e d r e m n a n t s
e a t both
by
tide-pool
6.0-6.9 cm)
that
at
species
at high
although
observed
cinctipes
to the high i n t e r t i d a l
site
of t h e
site
this
small
length
bits
zone . ( s e e C h a p t e r
predators,i parasites
a
did
species,
I
of t h i s
from
I
octopods
(individuals
i t
Island
of
Island
(total
and
study.
velata,
size
or
(probably
e n t r a n c e s of s m a l l i n t e r t i d a l
no e v i d e n c e t h a t
during t h i s
Diana
California,
den
Large perch
maculosus,
encounters
this
limit
boulder i n t e r s t i c e s
abundant o v e r t h e
small
body
abundant
lower
f o r a g e d over t h e Diana
Oligocottus
of
was
defined
(Table I ) .
entering
laboratory
which
High
to
the
that
vermiform
P.
cinctipes
25
Discussion
It
my
i s clear
data, that
ranges
in
from
o b s e r v a t i o n s made by H a i g
b o t h P e t r o l i s t h e s - s p e c i e s have d i f f e r e n t
the
intertidal
zone.
p o s i t i o n s o f the l o w e r l i m i t
limit
Juveniles
nearly
zone
appear
to that
total
and
absence
that
high
narrow
1978),
o f P.
absence
but i n f a c t
the
reason f o r
interactions
lower l i m i t
these
were
In
in
subtidally,
(+0.6
2 and
wide v e r t i c a l
m)
which
are
3),
The
intertidal
zone,
r e p r e s e n t s an
abundance.
r a n g e s from
below datum
contrast
upper
subtidal
r a t h e r than
occur
the
within
(Paine
a
the
1974,
relatively
to the
lower l i m i t
of
o f t h e m u s s e l band
represents
an
breaks
Suchanek
severe,
the
i n the lower
limit
abundance
sharp
and
the shallow
meters
most
band.
( P a i n e 1974,
reproduce
from
vertical
show t h a t
ranges
(Figs.
cinstipes
several
discontinuity
predation
adults
from
( T a b l e I) .
vertical
of d i s t r i b u t i o n
to
intertidal
cinctipes,
abrupt
inhabit
are able to inhabit
intertidal
Suchanek
The
data also
P. c i n c t i p e s
i t s observed lower
abrupt d i s c o n t i n u i t y
Mussels
to
of c o n s p e c i f i c
i t s complete
suggests
R*
of
My
o f P. e r i o m e r u s a r e t e m p o r a l l y s t a b l e
identical
(1960) and
rather
were
1978).
mussels
providing that
than
distribution.
competition
Although these
were
able
r e f u g e from
to
and/or
biotic
grow
predators
and
was
available.
The
total
absence
o f P. c i n c t i p e s
subtidally
suggests
that
26
either
extremely
conditions
habitat
tidal
below
selection
survive,
this
+0.6
I
in
will
an
show
later
survive
or both of
that
this
below
species or
lower
the
inter-
first
two
s p e c i e s can not o n l y
+0.6
m,
factors
refuting
the
i s the cause of
o f P. e r i o m e r u s r e p r e s e n t s a
show t h a t
probably
at l e v e l s
d a t a below t o s u p p o r t
of t h i s
neither
were o b s e r v e d h i g h e r
distribution
to this
physical
break.
the v e r t i c a l distribution
chapter
occur,
and i s used t o a v o i d
intolerance to physical
distributional
this
intolerable
but i s able t o reproduce
that
species
to
are
interactions
areas f o r e i t h e r
The.upper l i m i t
in
m
biotic
has evolved
and s u b t i d a l
reasons,
idea
effective
adults
t h a n +0.9
represents
species.
m.
This
an i n a b i l i t y
hypothesis.
Data
break
presented
nor j u v e n i l e s
above 0. 9 m a b o v e datum.
this
sharp
of
this
sharp break i n
of this
species
I will
present
27
II,.
TRANSPLANT
EXPERIMENTS
Intro-duct i o n
Individuals
distance
to
of
above t h e
determine
p o s i t i o n s on
P.
upper l i m i t
the
beach.
and
limit
i t s population
was
yes,
the
rarity
absence
of
were
the
At
reproduce
then b i o t i c
of
this
the
at
transplanted
P.
w h e t h e r t h i s s p e c i e s can
survive
of
eriomerus-
live
I f the
s p e c i e s i n the
low
population
P.
the
this
lower
question
most l i k e l y
i n t e r t i d a l : . and
high
cinctijoes
l e v e l s below t h e
answer t o
f a c t o r s would be
short
at abnormally
same t i m e , c o u l d
intertidal
band?
eriomerus
a
cause
its
of
total
subtidally.
M e t hod-s -
Transplant
Cages and
Crabs
stainless
10.2
cm
percent
same
were
Experimental-Animals
transplanted
s t e e l wire.
and
had
of the
material.
same manner a s
These
s u r f a c e was
cages
open.
for
the
collected
within the
vertical
both
m i d d l e and
distributions
x 0.6
Cage l i d s
with
herring-roe
of
which
measured
0.6
Cages were f i l l e d
animals
respective
cages
mesh o p e n i n g s o f
Experimental
from
in
30.5
cm..
made o f
x
30.5
of
collected
milk-basket
Petrolisthes- species
lowest
in
the
portions
x
Seventy-six
were made
rocks
and
were
the
in
the
traps.
were
of
their
intertidal
zone.
28
N i n e males
crabs
by
and n i n e f e m a l e s were p l a c e d
collected
caliper
to
the
at the transplant
nearest
site
t h e c a g e s and were r a n d o m l y
grabbing
individuals
from
J.976
the
day
following
cages'
sides.
at
above datum.
each
One
P. c i n c t i p e s .
lowest
( 0 . 3 m)
all
1976.
spring
inclusive.
of f o u r
were
cages
were
A
which
contained
of
at
final
the
to their
observation
counts
embryos
were
of
and 1.6 m
the
( 1 . 6 m) and a t t h e
on
lower
1976.
12 May
low
The
1976.
water
on
a t l o w e r low w a t e r o f
until
26 September
1976
was made on 15 A p r i l 1 9 7 7 .
survivors
made.
one
P. e r i o m e r u s ,
on 15 A p r i l
established
followed
line
about
0 . 3 , 0 . 9 , 1.3
levels:
A l l c a g e s were examined
tides
fishing
two c a g e s
Cages a t t h e h i g h e s t
levels
observations,
returned
blindly
was a g a i n c h e c k e d on t h e
I placed
a t 0.3 and 1.6 m were examined
stages
placed
site.
them w i t h woven
l e v e l s were e s t a b l i s h e d
intermediate
During
by
were
Transplant cages
Island
Cage c l o s u r e
of the
other
12 May
30 min o f b e i n g
a dishpan.
data c o l l e c t i o n .
apart
Those
(measured
Experiments
to
two
These
Crabs
a s s i g n e d t o a cage
L i d s were s e c u r e d by l a s h i n g
meter
0.1 mm).
within
p l a c e d among b o u l d e r s a t t h e D i a n a
The
cage.
h a d maximum c a r a p a c e w i d t h s of 1 1 . 5 t o 14.9 mm
vernier
into
i n each
and
developmental
C r a b s were i m m e d i a t e l y
c a g e and t h e l i d s e c u r e d .
29
The
1977
Experiments
The
steel
following
stove bolts
lashing.
No
experiments
changed
R'
m o d i f i c a t i o n s were made i n 1977.
s e c u r e d the l i d s
lids
(see
t o 0.3,
eriomerus
of
the
r e s u l t s below).
0.6,
were
contained
P.
0.9
and
placed
1.2
The
were
examined
at
29 A u g u s t
1977
and
two
low
on
water
scale.
s t a g e s were
The
features.
features
first
three-quarters
about
half
about
y o l k and
yolk.
the
two
m
P.
of
datum.
levels.
cinctipes.
collected.
These
and
cages
were
spring
tide
series
until
beat.
Also,
on
a
five
embryos had
moved
category four
were
scored
about
eggs
which
signs
distinct
and t h e i r
Embryos i n t h e t h i r d
Embryos
category
were no c l e a r
ommatidia
ommatidia
o n e - q u a r t e r y o l k and
prodded.
cages
1977
measured
i s , there
with u n d i f f e r e n t i a t e d
heart
1.2
c a t e g o r y i n c l u d e d eggs
Category
about
obvious
of each
were
m above
contained
6 April
levels
Stages
homogeneous t h r o u g h o u t , t h a t
larval
one
1977
inclusive-
Developmental
nominal
and
and
of
the
Two
a t 0.9
the only information
started
lower
Deyelopmental
instead
transplant
m above datum.
a t 0.6
eriomerus
Number o f s u r v i v o r s was
experiments
cages
were f o u n d t o have come open d u r i n g
T h e r e were t h r e e c a g e s a t each o f t h e 0.3
Two
Stainless
of
larval
volumes
were
c a t e g o r y were
distinct
as
was
i n category four
within
were
the
hatched i n the
eggs
an
were
i f
laboratory
30
w i t h i n about
one
weeJc.
of nongravid
females-
Finally,
the f i f t h
category
consisted
Results
Survival
o f T r a n s p l a n t e d P.
Results
presented
transplanted
t o 1.3
and
survival
rates
below
m a b o v e datum
0.9
replicates
at
which
1.6
eriomerus
in
1.6
Fig. 4
m xn
1976
in either
and
1.3
m
relatively
survival
r a t e s o f P.
( F i g . .4)
by
four
0.6
between
between
eriomerus
m
survival
data
observed
by
suggest
conditions
upper
and
24
August
because
which
of
1976
eriomerus
29
July
placed
and
August,
exist
the
eriomerusas
little
The
survivor
was
t o be
clearly
curve
accounted f o r
had
become
The
1977
lower than
greater
P. e r i o m e r u s r e p l i c a t e s
P.
show
( F i g . 4).
1976.
m appear
and
I
again
of a l i d which
m rates are
t h e two
that
limit
and
0.9
In
1976
had
than those at
eriomerus
P.
eriomerus
m i n 1977
replicates
m
r a t e s a t 0.9
( F i g - 4 ) , but the
physical
site.
escaped
these
0.3
28 J u l y
those demonstrated
These
the
28 J u l y
c r a b s which
untied
P.
of
lower
P.
above datum i n May
from
deflection
that
t o 1.2
year.
Results
sharp
and
were c o n s i d e r a b l y
respectively.
low
show
at
at
than
1.2
m-
cannot
tolerate
the
as
m
the
0.3
above
p o p u l a t i o n a t t h e Diana
Island
31
Figure
4.
Survival
rates
l i n e s with closed
lines
are indicated
1976
data
triangles
the
circles refer
w i t h open c i r c l e s t o P.
levels
the
of t r a n s p l a n t e d
1977
squares
Vertical
(1.3 m)
(1.2 m)
(P. c i n c t i p e s
arrows
tidal
ranges
solid
arrow
e r i o m e r u s . Two
graph
and
P.
eriomerus
P. e r i o m e r u s
species.
eriomerus.
solid
from t h e
top:
and
open
respectively),
i s represented with c l o s e d
and
Dashed
different
i s r e p r e s e n t e d by c l o s e d
on t h e r i g h t i n d i c a t e
of both
P.
t o P. c i n c t i p e s ,
i n the second
(P. c i n c t i p e s
data
Petrolisthes»
and
open
respectively) .
approximate
Dashed a r r o w ,
P.
inter-
cinctipes;
32
20
10
5
1*6 m Above
-1
1
L
Datum
1 1 1-1I1 I l i i ' •
I
20
10
5
1.2 m (•,.)
1.3 •m ( A , A )
1
<l»
>
— J
1-
I
L_
J I -1
1_ 1 I 1 I 1_
20
0.9 m
10
5
cz
0.9 m
1
-J
1
1
1
1
L_
1
I
I
I
I
I
i
I
I
I
I
20
1015
0.6 m
11—i—_i_ i_ i_
—i—,_i 1 i i i ' '
2 0 r ^
0.5 m
10
0.3 m
A M
-j—i—i—1_
i i i ' 'M A M i J i J i A i
J J A S O N D J F J—i—i
1976
1977
33
Embryonic
Data
Development
of T r a n s p l a n t e d P.
eriomerus
p r e s e n t e d i n T a b l e I I I show t h a t
d e p o s i t e d and
levels.
h a t c h e d eggs a t
When
the
0.3
m
the
0-3
P.
eriomerus
and
transplant
0.9
cages
females
m
transplant
were
established
Table I I I . Developmental s t a g e s of the eggs h e l d
Y R- e r i o m e r u s f e m a l e s a t t h e 0.3 and 0.9 m t r a n s plant levels.
The a b b r e v i a t i o n ng s t a n d s f o r n o t g r a v i d .
D
n
category:
15 A p r i l
12 May
29 May
2
3
4
n
1977
(15 A p r i l
1976),
category
one
first
developmental
were
either
3
4
4
0
1
2
0
4
9
9
8
1
0
0
8
2
2
0
3
0
0
3
0
0
1
6
5
5
5
2
1
2
3
2
1
0
0
1
0
1
0
0
1
1
7
6
6
1
0
2
5
3
2
0
1
1
1
2
0
0
0
1
5
5
4
0
0
5
0
0
0
0
1
0
6
6
3
0
1
5
1
0
1
0
0
1
On
(0.3 m)
2
4
2
eggs.
females
1
0
0
most o f t h e f e m a l e s
these
ng
9
8
1976
30 J u n e
29 J u l y
26 Aug
26 S e p t
5 April
ng
12
May
b o r e embryos
c a t e g o r y , and
nongravid
or
bore
(8/9)
at t h i s
level
bore
( T a b l e I I I ) more t h a n h a l f
which
on 30
matured
beyond
June the m a j o r i t y
category
one
eggs.
of
the
(6/7)
This
34
suggests
that
a hatch
(Table I I I )
beginning
six
eggs.
session
second
(0.3
females
The
26
September
(Table I I I ) .
(1964)
this
who
category
strong
occurred
26
heart
beats,
was
following
but
between
this
are
two
12
Sound,
species
further
(5 A p r i l
or
similar
1977,
and
i s able t o reproduce
III)
was
four
the
of
category
to
0.9
m
above
September
of
1976
Knudsen
season f o r
observed
appeared
the
third
reproductive
those
I
a
investigated
reproductive
supporting
Table
activity
not
26
Washington.
Females
July
suggest
was
to
29
bore
separate
May
b r o o d s i n one
successful.
year
August
(Table III)
least
These r e s u l t s
i n Puget
and. by
data
On
reproductive
f o u r embryos f r o m b o t h l e v e l s
hatching
this
at
o b s e r v e d two
species
June.
eriomerus transplanted
datum a l s o d e m o n s t r a t e d
which
m)
activity,
Petrolisthes
sessions
of
t o 30
were e i t h e r n o n g r a v i d
of reproductive
further.
prior
mode
at t h i s l e v e l
remaining
one
a
occurred
that
n o r m a l and
conclusion
became
again
had
that
ovigerous
the
suggesting
within i t s entire
that
intertidal
range.
Survival
of T r a n s p l a n t e d
Petrolisthes
all
l e v e l s to
suggesting
lower
30
P.
c i n c t i p e s demonstrated
which t h i s
that
limit.
Inlet
species
was
high
Furthermore,
results
transplanted
( F i g . 1), suggest
to
survival
transplanted
i t i s p h y s i o l o g i c a l l y able
c i n c t i p e s were
Bamfield
P. c i n t i p e s
to
2.8
that this
m
below i t s
study
below
species
at
(Fig. 4),
survive
of a p i l o t
rates
in
which
datum
in
i s able
to
35
survive
of
a t depths
which
populations
transplanted
healthy.
that
of
this
species.
P. c i n c t i p e s
were
Embryonic
Development
at the
conditions
highest
and
intertidal
levels
below which
onset
of
these
experiments
levels
bore c a t e g o r y
May
had
1976
On
a t 0.3
one
surfaces
of
suggesting
Also,
on
t h e 0.3
otherwise
these
appeared
eggs
eggs
transplanted
1.6
at
normally
were
suggesting
occurs.
(15 A p r i l
1976,
half
Table
of the females
females
were
(easily
two
gravid,
and
27
observable
effect
On
at
28
either
eggs o b s e r v e d
on
27
both
On
at
both
m and
on
one
hatching
the
posterior
no
at
ovaries
through
and
had
1.6
were
ventral
thorax),
oogenesis.
f o u r embryos o f f e m a l e s
These embryos a p p e a r e d
beats.
nongravid
Their
the
category
suggesting that
June.
abdomen
at
At
IV).
there
m levels.
that
and
n e a r l y a l l of t h e f e m a l e s
transplantation
heart
(0.3
cinctipes
s p e c i e s i s able t o reproduce
27 June I e x a m i n e d c a t e g o r y
and
levels
P.
matured b e y o n d
membranous
that
cintipes
m.
about
May
suggest
1.6
i t
m which were n o t
the
strong
females
days,
embryos which had
o c c u r r e d between 28
with
of
this
( T a b l e IV)
27 J u n e
filled
had
that
were c a r r y i n g
female
194
grew.
lowest
suggest
one.
and
of T r a n s p l a n t e d - P .
T a b l e IV)
levels
alive
some o f t h e i n d i v i d u a l s
Reproductive
28
After
limit
A l s o , r e m n a n t s of e x u v i a p r e s e n t i n t h e c a g e
at l e a s t
females
a r e c o n s i d e r a b l y below t h e l o w e r
July
more t h a n
level
normal
and
half
the
(Table I V ) ,
June had
at
hatched
of
again
prior
to
36
T a b l e I V . D e v e l o p m e n t a l s t a g e s o f t h e e g g s h e l d by
P. c i n c t i p e s f e m a l e s a t t h e h i g h e s t and l o w e s t t r a n s plant levels.
The a b b r e v i a t i o n ng s t a n d s f o r n o t g r a v i d .
1.6
m
0. 3 m
n
n
nq
1
2-
3
4
9
9
9
1
2
0
8
7
5
0
0
3
0
0
1
0
0
0
9
9
9
0
0
0
8
7
7
2
5
6
2
1
0
0
0
0
2
1
1
2
0
0
9
9
9
7
7
7
0
0
7
0
0
0
0
0
0
9
8
category:
15 A p r i l
12 May
28 May
1976
27 J u n e
28 J u l y
24 Aug
26 S e p t
5 April
this
time.
remaining
hatched
26
1977
At
the
females
since
m
level
collected
four
on
females
bore
a l l
September.
0.3
1.6
m
level
category
females
on
26
24
August
September
had
at
this
bore
that
observation
at l e a s t
beginning
on
one
date.
s e s s i o n of
15 A p r i l
1976
3
4
9
9
4
0
0
4
0
0
1
0
0
0
1
6
5
0
3
4
1
0
0
4
0
0
3
0
0
7
1
0
7
0
0
1
0
1
0
August-
level
category
hatches.
two
one
that
reached
seven
presumedly
at
eqqs.
two
I t i s not
Data p r e s e n t e d
and
of
females
females
reproductive
one
had
were n o n g r a v i d
of n i n e
(0.3"m) s u q q e s t
successful
2
t h r e e e g g s which
became o f embryos w h i c h t h e o t h e r
previous
24
In c o n t r a s t , f o u r out
on
net
on
the
Data
of
these
known what
carried
on
the
i n Table
IV
show
activity
occurred,
completion
around
37
24
August
at both
levels.
Discussion
I
that
have p r o v i d e d
P.
eriomerus
upper l i m i t
upper
related
(Haig
of
to the
from t h e
1960)
and
limits
of
1961b,
1970,
low
settlers
some
the
and
sufficient
Suchanek
not
band.
found
but
the
may
be
stresses
mortalities
of
P.
eriomerus
records
above i t s
adapted
to
life
are
known
to
set the
populations
(e.g.
predators
1974).
These
the
in
the
reproduction
limits
and
these
would
Because t h i s
observed
s p e c i e s was
total
growth-
that
conspecific
to
e l i m i n a t i o n of
were u s u a l l y
Furthermore, i f
i n d i v i d u a l s t o grow t o
occur
(Paine
o f any
lower l i m i t
not
1961a,
f a c t o r s found
since there
Petrolisthes cinctipes
the
of
were b i o t i c
i m m e d i a t e and
for survival
Connell
lower
i n v e s t i g a t o r s found
lower
case
adequate to allow
below
the
set
f e e d i n g time and/or
within short time periods
1978).
which
distributional
as t o c a u s e t h e
size,
m above
on
However, i n no
was
0.3
Based
below
opportunities
refuge
as
suggests
subtidal regions.
occurred
severe
little
Factors
s p e c i e s seems t o be
Paine
populations.
so
high
some i n t e r t i d a l
settlement
be
the
which s t r o n g l y
remain unresolved,
of reduced
environment.
and
Competitors
band.
t h i s population
this
intertidal
( F i g . 4)
s u r v i v e as
population
effects
abiotic
upper l i m i t ,
low
cannot
of the
limit
evidence
found
of
1974,
size
the
below
a
1976,
class
were
population
+0.6
m
and
38
because
and
and
and
+0.6
the transplant
experiments
r e p r o d u c e d below t h e l o w e r
Table IV),
i s used
m.
inhabit
nature.
conclude that
by t h i s
Clearly
a
I
much
limit
survived
of the p o p u l a t i o n
(Fig. 4
habitat
species t o avoid
t h e n , P. c i n c t i p e s
wider v e r t i c a l
showed t h a t a d u l t s
selection
intertidal
has e v o l v e d
regions
i s physiologically
range
than i t a c t u a l l y
below
able to
does i n
39
III.
ARENA
EXPERIMENTS
Introduction
Interspecific
vertebrates
from
can
preferred
(e.g.
lead
habitats
Jaeger
Similar
encounters
1971,
biotic
in
the
to
field
1971,
that
one
and
by
studied
the
that
dominant
stream
was
environment
conditions
evidence
unable
of
when t h e pond d r i e d .
that
exclusion
intertidal
by
species
species
was
excluded
hand,
the
stream
rigorous
t o burrow and e s c a p e
To my knowledge t h e r e
sets
either
was
i n t e r a c t i o n s with
i n the r e l a t i v e l y
interspecific
of
agonistic
upper
pond
lethal
is
no
behavior
or
lower
populations.
Molenock
Petrolisthes
(1976)
species
aggressive
between
to survive
On t h e o t h e r
species
adapted t o l i v i n g
t h e pond s p e c i e s
because o f i t s i n a b i l t y
among m o t i l e
limits
species.
1972).
freshwater
two
two
studies
Grant
among
ponds even t h o u g h i t was a l s o
He s u g g e s t e d
competitors
laboratory
review
of
terrestrial
of i n f e r i o r
occur
(1970)
small
i n h a b i t i n g streams because o f a g o n i s t i c
species
of
Heller
observed
streams.
from
i n both
Bovbjerg
and
restricted
t o the e x c l u s i o n
interactions
invertebrates.
crayfish
between
studied
and f o u n d
contact
individuals.
interspecific
intraspecific
that
s e v e r a l d i s p l a y s and
were used t o m a i n t a i n
She
interactions.
e n c o u n t e r s o f both
did
The
not,
spacing
however,
potential
for
types
distances
study
species
no
exclusion
by
nondestructive agonistic
c r a b s has n o t been
Random
individual
(Elliot
whether
patterns.
Mixed
for
preferred
of
the
the
s p e c i e s demonstrated
exclusion
o f P.
chose
to
outcome under
c o n d i t i o n s where t h e
potentially
saturate
by
the
extreme
conditions,
i t i s unlikely
density
combinations
of t h e two
a
P.
lower
that
i t would
to
from
combinations
the c o m p e t i t i v e
species
If
be
to
spatial
eriomerus
zoned
not
an
neighbor
designed
various
examine
of
a l l o w e d me
were
habitat.
P. e r i o m e r u s c o u l d
of
nonrandom
c i n c t i p e s by
Instead of t e s t i n g
I
presence
experiments
s p e c i e s arena experiments
densities,
P..cinctipes
the
position
s p e c i e s arena
each
habitats.
species
suggest that
influence
Single
determine
test
patterns
not
1971).
porcelain
studied-
spatial
does
b e h a v i o r among
could
exclusion
shown
of
under
these
occur at
lower
species.
Methods •
The
Arena
The
a
30.5
each
of
bottom
the
Seawater
a r e n a was
x
the tank
and
30.5
x
a 91.4
x 20-3
5.1
patio
( F i g . 5).
four
cm
depth
x 15.2
cm
elevated
A central
a t about
p l e x i g l a s s tank
block placed
Small diameter rubber
corners,
of the arena.
seawater
System
near
pillars
the b l o c k about
drain
5 cm.
with
The
one
a
corner of
placed
2 cm
from
standpipe
a r e n a was
with
located
at
the
kept
in a
41
Figure
5. The arena.
Seawater Line
Plexiglass Tank
43
floatshed
seawater
at the
was
mouth o f B a m f i e l d
pumped
from
brine-acid
pump
about
8 1/min.
Within
beach
over
which
undersurface
favorable
both
tossed
pile
i n t o the
have
enough
about
room
similar
Experimental
Diana
by
a
i n t o the
an
Little
arena
at
intertidal
occurred.
I have
to t h a t a v a i l a b l e
continuous
t o two
was
probably
since crabs
tank;
pf
their
on
the
the
to
traction
on t h e
third
on
most
plexiglass
and
These c r a b s would
those
themselves
were
usually
bottom d i d
m a x i l l i p e d s and
vertical
not
feed.
sides
of
the
Dodger
Channel
t h e emerged u p p e r s u r f a c e .
and
Holding - Procedure
animals
Island site
( F i g . 1).
plastic
on
Animals
Experimental
appeared
block
currents.
t o extend
never
Beale
the
c o r n e r s of the
block, but
up
was
move f o r l a c k
by
positioned
the
of
readily
Some c r a b s
or
flowed
species
s u b s t r a t e i n the arena,
bottom c o u l d not
near
level
Unfiltered
populations.
The
often
and
sea
10 m o f t h e f l o a t s h e d was
assumed t h a t s e a w a t e r q u a l i t y
natural
(Fig. 1).
2 m below
about
(model 3-MD)
Giant
boulder
Inlet
were
and
collected
i n the
from
channel
north
of
These c r a b s were h e l d i n h e r r i n g - r o e
dishpans
with
screen
flow of u n f i l t e r e d
h e a l t h y and
vigorous
covers
seawater
throughout
was
through
Cape
baskets
which
maintained.
Crabs
the h o l d i n g p e r i o d
months b e f o r e s u b j e c t i n g them t o t h e
arena.
a
of
44
Data C o l l e c t i o n
Arena
and
for
on
the
them
the
first
intervals
(k)
was
at
the
began by
undersurface
of the
h,
every
the
replicates
4.0
s t a b l e number
grand
the
were n o t
60
to
12.0
hour.
Counts
h
and
To compare
of c r a b s
under
the
at
of
0.5
h
12.0
h
equilibrium
block
calculated.
number of c r a b s
k was
h.
block
b l o c k were made e v e r y
observation times
made t h e n
c r a b s under t h e
least
v a l u e k was
mean o f t h e
three
h up
twelfth
fluctuations,
last
placing
for at
beyond
the
Analyses-
undisturbed
2.0
values i . e . the
initial
Statistical
experiments
leaving
crabs
and
under
after
This
value
the
block
for a l l replicates.
t h e mean o f t h e
last
If
three
observations.
Positions
of
crabs
b l o c k were mapped a t 72
the
to
sheet
at a p o i n t corresponding
outline
with
for
the
with
of the
the
later
block
tank
and
to the
was
drawn on
of the
block.
the
of
clear
placing
center
of
Prior
plastic
the
plastic
a dot
on
each
crab's
the
t o mapping,
s h e e t and
This outline
of
was
an
aligned
a reference
analysis.
Spacing
patterns
method
of
a random
of t h e a r e n a
I n d i a i n k m a r k i n g pen.
perimeter
the c a l c u l a t i o n
of
an
t o the undersurface
h by t a p i n g a s h e e t
tarp
carapace
bottom
clinging
C l a r k and
Evans
of a t h e o r e t i c a l
distribution
the sample.
(from t h e
This
plastic
maps) were a n a l y z e d
(1954).
T h e i r method
nearest neighbour
of p o i n t s having
theoretical
employs
distance for
t h e same d e n s i t y a s
nearest
by
neighbor
mean
that
is
45
compared
with
the
sample mean a s
the
ratio
Observed Mean/Theoretical
When
R =
1,
the
sample
points
Mean =
are
R.
spaced
randomly.
a p p r o a c h e s z e r o , sample p o i n t s a p p r o a c h a clumped
When R a p p r o a c h e s
1954)
sample
theoretical
with
the
allows
2.1419
points
standard
to
unity.
Evans
(1954) d i d n o t
of
An
expect
as
points
(i.e.
one
on
Therefore,
sample
aspect
order
the
To
of
variances.
make t h i s
were
measuring
nearest
and
a
be
degree
occurred,
smaller
I have
variance
one
one
on
presented
distribution
equal
be
different
and
When t h e
perfectly
This
that Clark
of
will
zero,
clumped
zero
when
manner
variance.
would e x p e c t
the
both
A
points
calculated.
patterns
also
Evans
of
significantly
variance
will
spacing
average
variances
that
than
in
comparison.
r e d u c e edge e f f e c t s ,
perimeter
Clark
distribution.
be
unity.
in
there
would
the
from
uniform,
other)
is
spacing
distributed
variances
to
sample c a n
discuss i s
i f nonrandom
theoretical
as t h e
R departs
are
uniform
R
distribution.
e r r o r f o r a random d i s t r i b u t i o n
points i s perfectly
the
a
d e t e r m i n e whether R
from
should
approach
same d e n s i t y
one
(=perfectly uniform,
As
not
used
neighbor
as
p o i n t s w i t h i n 3 cm
centers
distances.
were, however, used as n e a r e s t
of
of the
measurement
block's
when
These p e r i p h e r a l p o i n t s
neighbors.
46
Single
Species Experiments
These
size,
e x p e r i m e n t s were c o n d u c t e d t o d e t e r m i n e what
s e x and
equilibrium
controls
their
density
densities
of
f o r mixed
maximum
caliper
as
initial
assigned
limits
9.0,
and
12.0
were used
total)
species experiments.
carapace
class
w i d t h s which
Each
were t e s t e d
mm.
Mixed
Species Experiments
Also,
were s i m i l a r
experiments
single
and
and
as
128
of the
controls.
under
12.0
mm
P.
mm) ,
eriomerus
small
vernier
will
be e x p r e s s e d
was
arbitrarily
of
were
either
tested:
species
32 c r a b s o f e a c h s e x
the s p a t i a l
patterns
size
under
respectively).
(50, 60
(64
of
o r 64
crabs,
one
Either
the
block
Appropriate
respectively)
s p e c i e s e x p e r i m e n t s were r u n
class,
species)
the arena block.
were p l a c e d
crabs,
Mixed
32 f e m a l e s o f e a c h
large
12.8
120
species experiments
served
males
100,
by
by
were d e s i g n e d t o d e t e r m i n e whether
60 o r 64 c r a b s o f e a c h s p e c i e s
(totals:
s e r v e d as
t o t h o s e o f males a l o n e .
s p e c i e s e x c l u d e d t h e o t h e r from
50,
males
t o d e t e r m i n e whether
sex
These
class
and
sized
were measured
Three s i z e c l a s s e s
class.
mixed
also
C r a b s were
size
Forty-eight
size
patterns
They
Size classes
o f ±0.8 mm.
f o r each
groups
mm.
marks.
15.0
on t h e s p a c i n g
both s p e c i e s .
t o t h e n e a r e s t 0.1
their
had
effect
on
males
of the
(14.0-15.4 mm)
and
12.0
mm
females
size
(32
P. e r i o m e r u s -
(11.3-12.8 mm)
males
class,
v s . s m a l l P. c i n c t i p e s
vs.
on
on
(11.3large
47
R'
cinctipes
to
17.0
(14-0-15.4 mm)
mm.
slightly
These
different
c r a b s of each
block,
two
were
on
experimental
placed
to the
males which r a n g e d
14.0-17.0 mm
species, sixty
perpendicular
Behavioral
and
seawater
were
conditions.
were
side
males
used,
by
and
side
inflow
0,
experiments.
4,
I
describing
and
Instead of
64
with t h e i r
of
one
long
axis
( F i g . 5).
48 h a f t e r
during
recorded
encounters
aggressive
I
noted
or i n t e r s p e c i f i c ;
have
used
the
the various types of behavior
experiments.
by
min
during
winning
encounters
and
mixed
were
which s p e c i e s
o f Molenock
observed
kept
30
For the
i f interspecific,
terminology
the
by c r a b s
encounters.
whether
of a l l arena
during
moved
intervals
r e c o r d s were
of b e h a v i o r used
distance
min
the s t a r t
species experiments,
as t h e t y p e s
experiments
intraspecific
24
aggressive
I also
crabs
species
won.
of
as w e l l
encounters.
losing
1,
In s i n g l e
number
interval
to
Observations
began
on t h e
14.0
subjected
instead
B e h a v i o r a l o b s e r v a t i o n s were made d u r i n g 30
which
from
(1976)
during
when
these
48
Results
Single Species
Tables
Experiments
V
and
VI
show
range t e s t e d ) , or sex
tested.
Table
randomness
direction
is
o f even
nonrandom
consistently
and
both
out
spacing.
lower
tended
f o r both
size
alone
to
than
sample
were
not
(p<0.05)
species)
from
were i n
that
variances
theoretical
the
have nonrandom
A d d i t i o n a l evidence
from
(over
spacing
which
variances
the
were
(Tables
V
VI).
The
Observations
mechanism
causing
maintenance o f n e a r e s t
observed
that
species to
four
maintain
others).
Two
Chelae shove
2.
females
w h i c h were d i f f e r e n t
of t w e l v e
comes
Some B e h a v i o r a l
with
species
A l l cases
(eight
r e g a r d l e s s of
(P. e r i o m e r u s
VI),
distributions.
that
neighbor
types
these
of
involved
towards
the
contact.
3.
behavior
crab
the
(display):
i n t r u d i n g crab
e i t h e r b a c k s o f f or t a k e s
Cheliped
distance
contact
(contact):one
probe
nonrandom
distances
i t s c h e l i p e d , pushing
Cheliped
this
grasp
i s active
individuals.
I
were o f t e n used by
both
two
delivers
Molenock
1976
for
involved display:
rapid,
powerful
1.
jabs
retreating
crab
from i t s space.
chelipeds
are
fully
at f u l l
the
by
(see
and
spacing
gape.
challenge
and
( c o n t a c t ) : one
extended
The:receiving
makes
or
both
crab
aggressive
chelipeds
49
T a b l e V.
Nearest neighbor s t a t i s t i c s f o r
c i n c t i p e s . A s t e r i s k s mean t h a t p<0.05.
R-
of
n
obs.
mean
(mm)
obs,.
S2
(mm )
theor.
S2
(mm )
48
48
26
27
28. 2
25. 1
36.7
30.5
157.7
151. 9
1. 17 ns
1.07 ns
12.0
12.0
12.0
12.0
12.0
12.0
48
48
64
64
84
84
30
20
36
26
40
28
31.2
31. 1
27.8
34.0
27.0
28.3
92.4
80.6
42.3
64.3
28.6
51. 1
136. 7
205.0
113. 9
157.7
10 2. 5
146. 5
1. 40 *
1. 29 ns
1.36 *
1.42 *
1. 44 *
1-23 *
m
m
15.0
15. 0
48
48
20
22
32.8
35.7
34.9
44.5
205.0
185.6
1. 20 ns
1,41 *
f
m+f
12. 0
12.0
29
29
31.6
28. 5
41.9
6 0.4
141. 4
14 1. 4
1. 39
1. 25
sex
size
class
initial
density
m
m
9.0
9.0
m
m
m
m
m
m
the
receiving
respectively
held
for
held
either
it.
4.
this
48
32+32
of the other
are
clenched
crab.
s e v e r a l seconds.
Cheliped
rock
The
with
the
oscillated
crab
of vibrating
about t h e middle
cheliped(s)
is
Molenock
(1976)
My o b s e r v a t i o n s
This axis intersected
usually
holding
describes
differ
the c h e l i p e d s , the e n t i r e
of the carapace.
*
w h i c h was
w h i c h was
a r o u n d an a x i s p e r p e n d i c u l a r
which i t was s t a n d i n g .
#
by t h e c h e l a o r c h e l a e
the crab
(display):
a s c h e l i p e d movement o n l y .
Instead
R
2
Once r e l e a s e d , t h e c r a b
r e t r e a t s or f i g h t s
hers.
on
crab
2
from
body o f
to the surface
a
point
at
The c h e l i p e d s a r e r e t r a c t e d
50
Table VI. Nearest neighbor s t a t i s t i c s f o r
P. e r i o m e r u s . A s t e r i s k s mean t h a t p<0.05.
n
(mm )
theor.
s
(mm )
48
48
16
15
38.7
39. 1
82.5
42.8
256. 3
273. 4
1. 26 ns
1. 24 ns
12.0
12. 0
12.0
12.0
12.0
12.0
48
48
64
64
84
84
10
13
13
11
16
12
55. 1
45.3
45.8
4 4. 3
43.3
45.6
85.4
212.0
132.7
236.9
94.0
50.3
410.0
315.0
315.0
372. 8
256. 3
341.7
1. 42 *
1. 33 *
1. 34 *
1. 20 ns
1.41 *
1. 29 ns
15. 0
15.0
48
48
13
15
53.5
43.9
315. 4
27 3. 4
1.57
1.39
*
*
1. 37
*
sex
initial
density
m
m
9.0
9.0
m
m
m
m
m
m
m
m
short
Sometimes
2
184.9
132.5
32 + 32
12
48. 6
341.7
232.3
retreated
autotomize
oscillations
Both
presence
antennae.
or
the
ceased
fought.
during i n t r a -
sight
and
o f an i n t r u d e r .
Each antenna
both
are
while
important
crab
species readily
the f i e l d ,
or i n t e r s p e c i f i c
touch
quivering.
The " r e c e i v i n g
Although
from
of
momentarily
receiver.
c h e l i p e d s when c o l l e c t e d
this
Oscillations are
and g i v e t h e c r a b and a p p e a r a n c e
these
R
—
advancement was made on
observe
2
2
a g a i n s t t h e body w h i l e o s c i l l a t i n g .
and r a p i d
either
s2
—
n.a.
f
f+ m 12.0
tightly
obs.
obs.
mean
(mm)
size
class
spacing
I
d i d not
encounters.
i n determining the
C o n t a c t i s made by t h e l o n g
s c a n s an a r c s l i g h t l y
flexible
g r e a t e r than
180
51
d e g r e e s and i s l o n g enough
from
the
usually
rear.
turned
(antennal
markedly
sensory
device
noted
on
contact
rear
the
approach
species
From
was
the crab
Antennal
activity
1976) i n c r e a s e d
t h e importance
territorial
of
territoriality
observations
the exoskeleton
were
in
and d e f e n d e d a f i x e d
were
never
the
area
of
this
crabs.
s e n s e t h a t an
(violating
g i v e n by Brown
the
and O r i a n s
which were made a t 12 h i n t e r v a l s
t h a t n a t u r a l l y marked c r a b s
Molenock
was f e l t ,
t a p , Molenock
indicating
approaching
i n d e t e c t i n g t h e presence o f nearby
acguired
markings)
intruders
intruder.
antennal
encounters,
condition
1970).
a
faced
and
during
individual
first
and
lash
Neither
When
to
the
in
most
the
(1976) who o b s e r v e d
(barnacles
common
a n d / o r worm
types
same p l a c e .
of
I
tubes
natural
T h i s agrees
with
incessant exploratory behavior
by
Petrolisthes.
Interspecific
Tables
tained
R-
V
and
a greater
cinctipes.
intervals
P.
Differences
VI show t h a t i n d i v i d u a l
mean d i s t a n c e
The
only
to
nearest
overlap
( F i g . 6) i s between
of
P. e r i o m e r u s
neighbor
the
95%
15.0 mm P. c i n c t i p e s
main-
than
did
confidence
and
9.0 mm
losers
during
eriomerus.
Distances
intraspecific
possible
traversed
fights
mechanism
between
by
12 mm
f o r the
winners
males
differences
and
( F i g . 7)
suggest
i n spacing
a
patterns
ure
6.
single
at
Distance
species replicates
initial
lines:
to nearest
densities
o f 48
neighbor.
per
size
crabs.
means; v e r t i c a l l i n e s : 95%
R e s u l t s are from
class.
Data from
two
male
Horizontal
confidence
intervals.
53
(UJUJ)
SDUE^SIQ
JoqgSiaN
issjeaN
54
Figure
7.
D i s t a n c e s moved by
crabs during
encounters.
Data
collected
experiments
from
the
12.0
from
mm
single
size
intraspecific
species
class.
arena
ADVANCES
80
RETREATS
n=4l
n = 32
P. cinctipes
401
u
c
OJ
ZD
cr
<U
801
40 i
n = 28
n = 20
x
x
P. eriomerus
0
20 40 60*
0
20
40 60•
Distance Moved (mm)
56
observed
2*
between
cinctipes
those
of
P.
these
winners
two
advanced
eriomerus
during
that
average d i s t a n c e
greater
t h a n t h a t f o r P.
p<0.001) .
three
Losers
times
conspecific
that
intraspecific
greater
winners
w i n n e r s do
losers
after
necessary
spacing
not
the
patterns
the
even
by
P.
factors:
relatively
during
enforcement
relatively
spacing
to
P.
on
P.
test,
7 also
shows
eriomerus l o s e r s
was
both
about
species
traversed
pursuit
was
for
effect
motile
spacing
greater
of
point
species
in
patterns.
by
origin
as
of
of
which
are
spacing
P.
suggest
distances
to
by
two
winners
distances
eriomerus
a
agonistic
due
traversed
seem
non-random
neighbor
distances
individual
is
These data
( F i g - 6)
by
behavior
T h i s would
maintenance
nearest
eriomerus
travelled
of t h i s
completed.
the
distances
distances
The
greater
8 shows t h a t
the
starting
equilibrium values
c i n c t i p e s at the
values
approached
when t h e
most
Figure
than
test,
r e t r e a t s made
saturation
The
were l e s s
which
and
lose
disputes.
Figure
effect
greater
average,
Kruskal-Wallis
move a s f a r from t h e i r
relatively
maintained
which
encounters..
( F i g . 7) .
f o r any
the
c i n c t i p e s - l o s e r s (Kruskal-Wallis
interaction
causes
( F i g . 7,
r e t r e a t e d by
than
prereguisite
behavior
that
of
On
distances
winners
p<0.01)
the
species..
o f P.
density
(k)
same s t a r t i n g
has
f o r P.
p l a u s i b l e reason
density
for these
eriomerus
little
compared
d e n s i t i e s , suggesting
eriomerus-under the
starting
relatively
block
was'greater
were
than
d i f f e r e n c e s i s the
that
probably
48
crabs.
greater
57
Figure
8.
E f f e c t s of
were 48,
64
replicates;
and
initial
84
crabs.
vertical
density
Points:
lines:
on
k.
Initial
means o f
ranges.
two
densit
59
spacing
was
distance
not
the
increased
The
to
be
case
with
A
distance
by
fight
case
much
P.
cinctipes.
rates
the
fight
higher
the
first
Species
Results
are
and
eriomerus
those
P.
the
nearest
greater
spacing
be
expected
t o have a
to
be
eriomerus
had
c o n s p e c i f i c s than
did
P.
f o u r hours; at
and
In
P.
eriomerus
f o r P.
dropped
beyond f o u r
hours,
a d d i t i o n , the
eriomerus l e d to a greater
under
neighbor
the
block
higher
number
during
c i n c t i p e s (Table
of
the
VII).
Experiments
of
the
11)
had
p r e d i c t e d by
interspecific
that
in
the
arena
experiments
presence
of
P.
d i s p r o p o r t i o n a t e l y lower k v a l u e s
the
summarized
single species
in
k c i n c t i p e s / k eriomerus
mixed compared
c i n c t i p e s seem
a
r a t e of
case
values
This appears
r a t e with
of c o n s p e c i f i c s from
Mixed
P-
smaller
would
f o r both s p e c i e s .
r a t e of
P.
shown i n F i g . 9:
fight
This
equilibrium
maintains
fight
The
h o u r t h a n was
10
results
( F i g . 6).
density.
relatively
behavior
initial
first
(Figs.
since
r a t e i n crowded c o n d i t i o n s .
were s i m i l a r
exclusions
eriomerus
d e m o n s t r a t e d by
which
agonistic
during
initial
their
species
higher
sharply
P.
cinctipes
k values
to
b a s e d on
a
P.
by
increasing starting
much h i g h e r
distance.
the
for
related
higher
maintained
t o the
Table
VIII
increased
same r a t i o
controls.
where
when
of s i n g l e
the
cinctipes,
compared
These
species
to
results
the
two
show
ratio
species
k.
were
values.
60
Figure
9.
Fight
rates.
iments. P o i n t s :
l i n e s : r a n ges.
Data
from
means of two
single species
arena
replicates; vertical
exper-
200
Single Species
Arena Experiments
r
c
E
o
TO
150
o P. cinctipes
A P. eriomerus
100
CO
L
5.0±
O
u
4
24
Time at Start of Observation
48
Interval (h)
CD
52
Figure
10.
12.0
Mixed
mm
males o n l y
males and
single
species
females.
species
otherwise
arena
and
experiments. Results
a fifty-fifty
Data f r o m two
c o n t r o l s and
indicated)
f o r the
replicates
indicated);
lines:
vertical
for
replicates
mixed
P o i n t s : means o f two
mixture of
replicates
three
species
(unless
ranges.
are
from
12.0
the
(unless
test.
otherwise
mm
63
males and females
' males
single species control
A
mixed species test
A
O-
-O
60
ko46.2
k*453
30
B cipciipes'
0
1
1
'
-J—^-L-
E eriomerus
k=27.7
k=23.5
k»8w5
2
4
12
24
48
T i m e (h)
72
96
120
64
Figure
1 1 . Large
Points:
v s . s m a l l c r a b s i n mixed s p e c i e s e n c o u n t e r s .
means o f two
indicated);
vertical
replicates
lines:
(unless
ranges.
otherwise
B.
L a r g e P. c i n c t i p e s
Alone
••••••Mixed w i t h S m a l l
J
1
J.
'—/r—I
1
-J
I
P. e r i o m e r u s
:
.
'
D.
S m a l l P. c i n c t i p e s
Alone
Mixed with Large
01—i—i—i
2
i
4
i-
j
24
48
T i m e (h)
72
•
2
'
i—/f
4
i
i
24
\
i_
P. e r i o m e r u s
i
48
T i m e (h)
'
1
72
66
T a b l e V I I . F o r c e d and p a s s i v e e x i t s from u n d e r t h e b l o c k
d u r i n g t h e f i r s t hour o f i n t r a s p e c i f i c a r e n a e x p e r i m e n t s .
These d a t a a r e from males and f e m a l e s o f t h e 14-17 mm s i z e
c l a s s . I n i t i a l d e n s i t i e s u n d e r t h e b l o c k were 60 c r a b s .
Replicate i n parentheses.
time
interval
(min)
forced
cinctipes
0-15
15-30
30-45
45-60
0(0)
0 (0)
1 (0)
1 (0)
totals
Results
Table
of
experiment
of
this
in favor
P.
that
sex
was
o f P.
60
3(2)
2 (4)
2(1)
2(0)
0(1)
1 (0)
0 (0)
0 (0)
9(7)
1(1)
experiment
( F i g . 10
and
outcome:
the
Furthermore,
biasing
the
mixing
individuals
does n o t a f f e c t
eriomerus
(Table V I I I ) ,
a
mixture
almost doubled.
eriomerus
cinctipes
P.
sex
s p e c i e s with s m a l l e r
allowing
there
23(21)
fifty-fifty
(Table VIII)
passive exits
cinctipes
eriomerus
7(10)
3(1)
4(3)
9 (7)
2(1)
VIII) sugggest
k ratio
exits
eriomerus
by
P. c i n c t i p e s
this
large
( F i g . 11),
h to reach equilibrium
did
disproportionate
not
alter
reduction
the
in
and
by
before
adding
outcome
since
the
number
of
eriomerus.
The
space
mechanism by w h i c h
under
P.
cinctipes
the block i n r e l a t i v e l y
a c q u i r e s and
maintains
higher proportions
is
due
67
Table VIII.
O b s e r v e d k v a l u e s and t h e i r . r a t i o s .
With t h e e x c e p t i o n o f t h e d a t a f o r 14. 0-17. 0 mm m a l e s ,
these
r a t i o s have been
t a k e n from F i g s . . 1 0 and 11.
E x p e r i m e n t s i n w h i c h 14.0-17.0 ram males were u s e d ,
s h a r e d a common c o n t r o l . The a b b r e v i a t i o n s sm and l g s t a n d
f o r s m a l l (11.3-12.8 mm)
and l a r g e c r a b s (14.0-15.4
mm),
respectively.
(
P.
12 mm males
control
mixed
cinctipes
eriomerus
23.5
8.5
2.23
4. 44
27. 7
15.0
1. 88
3.02
31.0
11.0
1.73
3.70
13.7
2.5 3
e r i o m e r u s ; sm c i n c t i p e s
control
43.2
mixed
37.1
21.8
14.0
1.98
2.65
eriomerus; l g cinctipes
control
35.7
mixed
32.8
28.5
11.1
1.25
2.78
52.5
46.2
12 mm males & f e m a l e s
control
52.0
mixed
45.3
14-17 mm m a l e s
control
53.5
mixed
40.3
(both s p e c i e s
a d d e d a t t=0 h)
mixed
34.7
( c i n c t i p e s added
a t t=60 h)
lg
sm
to
k cinctipes^
k eriomerus
the
superior
defend
a spacing
during
30
ability
radius.
of
Of
individuals
104
min i n t e r v a l s b e g i n n i n g
of t h i s species to
i n t e r s p e c i f i c f i g h t s observed
a t 24,
48 and 72 h , e i g h t y
of
68
these
(77%) were won
greater
than
50%
by P. c i n c t i p e s .
(chi-square
This
is
significantly
t e s t ; p < 0 . 05) .
Discussion
Both
spacing
Petrolisthes
patterns
maintains
R-
a
(Table
greater
cinctipes (Fig.
differences
greater
is
winners
and
tend
V and V I ) .
distance
6).
that
distances
species
The
nearest
most
(Fig. 7).
Since
that
the
subsequent
even
spacing
defense
species.
The a d a p t i v e
behavior
were n o t s t u d i e d
require
a
to
are
of
an
here.
spacing
when p i l i n g
possible
radius
(Nicol
1932,
occurred
that
ensures
radius
and
the
the
s e a water c u r r e n t s
interstices.
This
could
from
porcelain
long
Wicksten
piles
adequate
through
especially
d e n s i t i e s of P e t r o l i s t h e s occur.
were
maintenance
this
crabs
setose
1972).
i n the corners
of these
laden
be
of
1957), i t
might a c c r u e
i n t o which t h e i r
oxygen and f o o d
where h i g h
these
maintenance
(Tinbergen
Certainly,
a n d i n d i v i d u a l s on the bottom
individual
for
does
b e n e f i c i a l t o both P e t r o l i s t h e s
feeding radius
It i s also
reason
individual
a d v a n t a g e s which
m a x i l l i p e d s a r e extended
feed.
than
the
likely
arena
eriomerus
e n c o u n t e r s t h a n P. c i n c t i p e s
is
T h i s became a p p a r e n t
P.
P. e r i o m e r u s - w i n n e r s a n d l o s e r s t r a v e r s e
space r e q u i r e s t i m e and energy
third
nonrandom
neighbor
likely
individual
minimum
maintain
In c o n t r a s t ,
to
in intraspecific
losers
to
of the
unable
of
an
passage of
the
important
boulder
i n areas
69
Both
species
behavior.
as
an
demonstrate
T h i s type
interspecific
of behavior
P.
zone.
would
interspecfic
arena
arena
be
P.
procuring
cinctipes
and
seems v e r y
unlikely
c a u s e d by
demonstrated
arena
a
a
eriomerus.
which
lower
inter-
for
space i n
opposite;
without
superior
ability
at
amount
of
In
conclusion, i t
d e l i n e a t e d lower
P.
that
species
disproportionate
sharply
species,
1967)
mixed
(Table V I I I ) .
e x c l u s i o n from a g g r e s s i v e
P.
the
the
eriomerus
expected
contestant
show
spacing
P.
(Miller
i t would be
However,
VIII)
t h a t the
intertidal
zoned c o n g e n i t o r ,
u s e d by
c i n c t i p . e s from the
dominant
maintaining
space i n the
higher
a
(Table
underblock
the
P.
experiments.
experiments
exception
c o u l d be
I f t h i s were t h e c a s e
eriomerus
ritualized
i n t e r f e r e n c e mechanism
might e x p l a i n the absence of
tidal
similar,
cinctipes
encounters
limit
(Table I ) ,
with
its
of
is
lower
70
IV.
RUN
EXPERIMENTS
Introduction
Laboratory
competition
the
between c l o s e l y
physical
the contest
experiments
environment
takes place
an e n v i r o n m e n t
cur over r e l a t i v e l y
One
purpose
of
competitive
related
species
1962).
The
steep g r a d i e n t s
short
distances
o f t h e r u n e x p e r i m e n t s was
interactions
on
in
offered
natural
environment
The
second purpose
whether
the
Petrolisthes
For
of the
observed
example,
when
a
an
run
were
and
species
vertical
Dawson
physical
1973).
of i n t e r t i d a l
ranges,
mid-intertidal
and
removing
middle
the
in
the
dominant
that
larval
recruitment
factors
oc-
by
high
to
of
both
selection.
i s provided
over a
according
to
gradient(s)
observed t h a t s i x
three
intertidal,
intertidal
neither
occurred
which
determine
habitat
vertical
of
of the a r e n a .
segregate
species,
effects
setting
was
(1975)
1968).
distributions
inhabited
t h r e e i n t h e low
is
and C a l v i n
l o c a t i o n s along the
Nyblade
i n which
zone
distributions
may
t h e l o w e r p o p u l a t i o n s expanded t h e i r
observed
by
than that
f a c t o r (s)
hermit crabs
two
influenced
t o determine the
caused
preferences for different
(King
of
in physical
experiments
continuous range, m o t i l e s p e c i e s
their
outcome
intertidal
experimental
vertical
populations
is
the v e r t i c a l
species
more
the
(Ricketts
both P e t r o l i s t h e s
a
that
(e.g. temperature, moisture)
(Park
i n which
indicate
different
one
zone.
After
the h i g h e r nor
ranges.
over
i n the
the
He
also
vertical
71
ranges
this
of
the
conspecific adult
recruitment
selection.
these
He
pattern
speculated
species
toward
resource' p a r t i t i o n i n g
to coexistence
A
would
be
reason
extremely
The
agile
three
Island
site
(Eicketts
dimensional
and
of
difficult.
imental
case)
one
led
and
that
has
led
Nyblade d i d ,
studied.
under r o c k s
The
and
Molenock
boulders
d i s t r i b u t i o n s of experimental
1975) .
a t the
sampling
are
Diana
of
I chose to
populations
both
examine
in
long
(runs) .
Because
of
Methods -
during the
differences
a p p a r a t u s between t h e
separately.
the
I
1968,
Instead
e x p e r i m e n t s were c o n d u c t e d
1977.
the
species
M a t e r i a l s and
Run
in this
like
Calvin
aspect
p a s t has
specialization
would have made t h e r e m o v a l and
vertical
enclosures
two
and
habitat
species.
experiment
the
fixed
i n the
i s t h a t P e t r o l i s t h e s occur
s p e c i e s d e s t r u c t i v e and
the
niche
intertidal
impractical for
for this
that competition
(habitat selection
removal
Nyblade i n t e r p r e t e d
genetically
greater
of these
species
as
zones.
two
years,
i n the
I will
summers o f
design
of
describe
1976
experthem
72
19 76
Run
Experiments
Construction
These
and
the
r u n s had
overall
were c o n s t r u c t e d
bottoms
C h a p t e r I)
of
by f a s t e n i n g
plastic
which
steel
measured
o f 1.50
together
herring
with s t a i n l e s s
perforations
dimensions
row
sections
baskets
bolts.
7.0
x 0.29
x 8.0
x 0.11
cut
m
from
(described i n
Walls of the runs
had
mm
30%
and
were a b o u t
opening.
A single
were
site
layer
collected
from
o f r o c k s was
from
a vertical
placed
the i n t e r t i d a l
range
which
was
into
zone
the
each
run.
Rocks
near t h e Diana
same as t h a t
Island
occupied
by t h e r u n s .
ISiSiiidal
Three
distance
the
was
runs
of the Enclosures-
were
positioned
o f a p p r o x i m a t e l y one
shore.
highest
Position
The
lowest
ends were a t 0.7
a mixed
controls.
species
test,
parallel
meter a p a r t
and
e n d s were a t 0.4
m above datum.
the other
two
t o each
other at a
perpendicular
to
m a b o v e datum, t h e
One
were
of the t h r e e runs
single
species
73
Experimental
Crabs
vertical
runs.
not
Animals
were c o l l e c t e d , w i t h o u t
range
Crabs
used
s m a l l e r than
in
perforations
species.
The
mixed
that
o f the s i n g l e
varied
from
Replicates
tides
were
by
dishpan.
on
Figs.
the
next
completion
of
of
reassiqnment)
from
spring
13 and 1 5 ) .
summer
their
through
the
1976.
a
in
unkown r e a s o n s
either
r u n c o n t a i n e d e g u a l numbers o f
sum
started
was e q u a l t o
the
The number
crabs
number
in
of experimental
the
into
lower
plastic
low w a t e r o f
dishpans
grabbing
and
individals
were p l a c e d i n t o a r u n a t i t s c e n t e r .
and t h e r u n s
tide
left
Crabs
next
undisturbed,
usually
( d u r a t i o n between r e p l i c a t e s
Eight replicates
replicate
the
during
t o a r u n by b l i n d l y
Crabs
c o v e r s were s e c u r e d
the
species
placing
from
until
were
60 t o 72 c r a b s p e r r u n .
a s s i g n i n g each
The
width
the chance of escape
species runs.
randomly
a
carapace
by t h e
s p e c i e s r u n s c o n t a i n e d e g u a l numbers o f
s p e c i e s , such
spring
maximum
occupied
Procedure
single
animals
10 mm
order to reduce
The
either
t h e same a s t h a t
within a
i n the run walls.
Experimental
both
approximately
r e g a r d t o s e x , from
were
remaining
were
replicate.
obtained
in
reused
Losses
were made up by c o l l e c t i n q
shown
during
the runs
at the
(after
random
which
occurred
additional
crabs
in
from
the f i e l d .
lost
during
No b i a s i n t h e p r o p o r t i o n s o f e i t h e r
either
y e a r was a p p a r e n t
(sign test,
species
p>0.2).
Counting
Counting
tion,
was
one s e c t i o n
r u n and w o r k i n g
section
1977
Run
a t a time, s t a r t i n g
towards
were i d e n t i f i e d
r o c k s from
each
from t h e l o w e s t end
the h i g h e s t .
C r a b s o b t a i n e d from
t o s p e c i e s and
counted.
Experiments
Construction
Run
frame,
dimensions
most
supported
of
a floor
basket bottoms.
net stapled
Intertidal
These
ned
a c c o m p l i s h e d by r e m o v i n g
were
which
was
3-66
x 0.135
constructed
made f r o m s e c t i o n s
of
x 0.105
m.
A
o f 19 x 13 mm
plastic
wood
stock,
herring
The s i d e s and t h e c o v e r were 10 mm
nylon
roe
fish
t o t h e frame.
Position
of the Enclosures
r u n s were p l a c e d
an i n t e r t i d a l
range
from
a t t h e Diana
Island
+0.1
m.
t o +0.9
site
and
span-
75
Experimental
Procedure
T h e r e were 72 c r a b s i n e a c h r u n i n e a c h r e p l i c a t e .
replicates
(Figs.
were o b t a i n e d .
14,A-E,G
contiguous
were 4-5
(Figs.
rocks
16,A-E, G)
over
the
entire
a
section.
14,F,H,I
and
1 6 , F H , I ) had two r o c k s
I determined
which was
rock
to
occurred
which
pairs
replicates
varied
from
single
three
on
crabs
the
by t h e c r a b s -
bottom
2
2 t o 56 d a y s
There
Counts
were
(Figs.
time
cm
2
of
similar
o f the arena
The
sec-
300
maximum c a r a p a c e
cm ).
of
replicates
had a p p r o x i m a t e l y
12.0 mm
per
row
per counting
showed t h a t d e n s i t i e s
2
0.00-0.04
pair
utilizable
(arena:0.02-0.04 c r a b s p e r c m ,
pairs:
other
r
c r a b s under t h e s e
those
The
that a rock
replicates
length of the run.
per
surface area
rock
contained
rocks
tion.
of
and
Euns i n s i x o f t h e n i n e
Nine
block
width;
between
14 and 16).
Counting
Counting
except
procedure
was
similar
t h a t t h e r e were n i n e e q u a l
Statistical
Analyses
Single
species
percentage
t o t h e 1976
experiments
length sections.
distributions
are
expressed
as
the
76
number
Mixed
s p e c i e s d i s t r i b u t i o n s a r e e x p r e s s e d as the percentage
number
To
o f c r a b s i n t h e i t h s e c t i o n X 100.
Number o f s p e c i e s A i n t h e r u n
detect
of species_A i n - t h e i t h s e c t i o n X
Number o f s p e c i e s A i n t h e r u n
differences
p r o p o r t i o n s i n each
transformation
(randomized
species
section
were
were
b l o c k s were a c o u n t
by
the
treatment
section taken
(eight:1976,
(Siegel
Tidal
the
1956),
to
arcsine
comparison
and
test
single
f o r a s p e c i e s and
the
total
number
of
nine:1977).
Spearman
which
the
Mixed
effects
'over
species runs,
will
rank
f o r e a c h s p e c i e s were
correlation
coefficient
tested
method
be d e s i g n a t e d a s r .
Experiments
During
apparent
portions
strip
subjected
treatments).
Depth-abundance r e l a t i o n s h i p s
for
and mixed
and t h e n a n a l y z e d by t h e p a i r e d
b l o c k s w i t h two
runs
replicates
between s i n g l e
100.
the
that
course
P. e r i o m e r u s -
of t h e runs
chart
of
the
from
experiments
i t
became
had a s t r o n g p r e f e r e n c e f o r l o w e r
(discussed
recordings
run
below).
Analysis
the Bamfield t i d e
of
gauge
tidal
station
77
( T a b l e X) s u g g e s t e d
one
of the t i d a l
results).
used
I
a sharp i n c r e a s e
parameters
movements
towards
what m a i n t a i n s
portions
test
vertical
to
laboratory
(Fig.
12)
tarp.
populations
were
in
front
o f each
each
tank
randomly
fifteen
14 mm.
which
tank.
one
of
were l e f t
starting
one
Maximum
A coin
flip
explaining
the
lowest
duration
exposure
on
Two
tidal
tanks
black
plastic
two h o l e s c u t
Onfiltered
seawater
through
species
carapace
at t h e s t a r t
in
t h e two s e c t i o n s
of
widths
of
Crabs
were f i f t e e n
each
were
m a l e s and
the
ranged
each
the
pumped from
3.0 1 / m / s e c t i o n .
There
into
two
from
replicate
tank
12 t o
decided
t h e two t a n k s was t o s e r v e a s t e s t
and c o n t r o l .
undisturbed i n the tanks a t l e a s t
24 h
before
the experiments.
Experimental
procedure
c r a b s i n t h e upper
half
with
pencil
wax
divided
in
behind a s c r e e n o f heavy
assigned t o the tanks.
compartments.
species
be
compensatory
possibly
experiments.
flowed c o n t i n u a l l y
of
make
might
(Table I ) .
a t a r a t e o f about
females
to
see
o f P. e r i o m e r u s , c r a b s were s u b j e c t e d
tank
placed
2 m below s e a l e v e l
Crabs
this
frequency;
sharp i n c r e a s e
levels,
O b s e r v a t i o n s were made t h r o u g h
tarp
of
zone
this
of frequent short
distribution
tidal
of
(exposure
when
lower i n t e r t i d a l
the effect
the
that
to determine
of the i n t e r t i d a l
To
studied
hypothesized
by P. e r i o m e r u s
between +0.6 and +0.9 m i n
grease
them
consisted
of each
into halves.
on
of
first
compartment.
the
outer
A few m i n u t e s
counting the
A
line
drawn
surface of the tanks
later
the
test
tank
78
Figure
in
12.
Diagram
o f one o f t h e t i d a l
centimeters.
tanks. Dimensions
are
79
Drain H o s e
80
was
drained.
observations
scurry.
Draining
showed t h a t
s t a r t e d a t 0900 h on e a c h
draining too f a s t
By d r a i n i n g t h e t a n k
detect
no
responses
Water l e v e l
draining,
was k e p t
at
period.
which
of
over a
crabs
at
the
time
the
5 min
to
half
caused
the
way
day.
some c r a b s
period,
receding
mark
could
line.
1 h
after
for
t a n k was r e f i l l e d
I
to
water
o v e r a 5 min
T h r e e r e p l i c a t e s were c o n d u c t e d , e a c h w i t h
of four
Prior
a
duration
days.
Results
Effects
of Mixing
Results
of
on P. c i n t i p . e s
the
P. c i n c t i p e s o c c u r r e d
species
IX).
run
1976
i n the lowest
trend
occurred
replicates
are considered
significant
differences
species
However,
the
(Table
section
show
(four)
in
(p>0.05)
percentages
for
into thirds,
there
any
the
i n s u c h a way
i s an o v e r a l l
third
Table
a l l
I X ) , there
mixed
o f P. c i n c t i p e s i n t h e h i g h e s t
fewer
o f t h e mixed
When
between
of
that
F i g . 13 and
1977.
( F i g . 14 and T a b l e
when s e c t i o n s a r e p o o l e d
run length
(p<0.05)
experiments
(mean d i f f e r e n c e = 14%, p<0.05;
A similar
single
run
nine
a r e no
species
nine
as
sections.
to
divide
increase
of the
and
o f 9%
test
run
IX) .
Reducing
apparent
t h e number
differences
in
of rocks
t o two per s e c t i o n c a u s e d
distributions
between
no
replicates.
ure
in
13.
Vertical
distribution
1976
the
highest
end
section
one
and
lowest
represent
the
distributions
l i n e s represent
each r e p l i c a t e
single
(days)
of
o f the
by
i n the
species
P.
run
cinctipes
i n the
i s represented
section
runs
by
f o u r . Dotted
lines
mixed s p e c i e s r u n s ,
solid
distributions.
i s shown on
the
Duration
individual
of
graphs.
83
Figure
in
14.
Vertical
distribution
1977
the
highest
end
section
one
and
lowest
represent
lines
the
distributions
represent
each r e p l i c a t e
single
(days)
of
o f the
by
i n the
species
P.
run
cinctipes
i n the
i s represented
section
nine.
runs
by
Dotted
lines
mixed s p e c i e s r u n s ,
solid
distributions.
i s shown on
the
Duration
individual
of
graphs.
Frequency (%)
85
T a b l e IX. P o o l e d mean p e r c e n t a g e s
(unblocked data)
o f c r a b s i n e a c h s e c t i o n o f s i n g l e and mixed s p e c i e s r u n s .
T h e r e were e i g h t r e p l i c a t e s i n 1976 and n i n e r e p l i c a t e s i n 1977
P. c i n c t i p e s
alone
mixed
P. e r i o m e r u s
alone
mixed
sectxon
+0.7 m
1976
+0.4
+ 0.9
1977
+ 0. 1
1
2
3
4
22
24
16
37
15
31
30
23
9
18
33
41
4
15
31
50
1
2
3
4
5
6
7
8
9
19
7
8
12
12
10
6
8
17
20
11
12
14
7
5
6
10
15
2
5
6
9
10
14
10
16
27
0
2
8
9
10
13
11
15
33
This
is
rocks
per s e c t i o n
(4-5
rocks
Preference
apparent
F i g . 14,F,H,I which had two
cinctipes
forintertidal
three
of a l l
other
replicates
F i g . 14,A-E,G).
f o r V e r t i c a l L o c a t i o n by_ P.
rank c o r r e l a t i o n
runs),
comparing
a g a i n s t the r e s u l t s
per s e c t i o n ,
Petrolisthes
preference
when
demonstrated
depth.
coefficients
cinctipes
From a t o t a l
(8+9 s i n g l e
were s i g n i f i c a n t .
little
o f 34
and 8+9 mixed
One o f t h e t h r e e
or
no
Spearman
species
coefficients
86
was
calculated
for a single
dle of the
t o p row;
from
1977
the
r
=
r
= -0.661).
different
of these
the
other
zero
preference
the
(Figs.
P.
15
f e w e r P.
in
and
16).
s e c t i o n s one
c o m p a r i s o n s were n o t
Reducing
apparent
the
of
the
( F i g . 16
rocks
per
14,E;
(Fig.
14,H;
results
provide
no
s p e c i e s has
a
The
abundance-
cinctipes
had
a
runs.
1976
i n 1977
in
1976
and
number o f P,.
mixed
species
t h e r e were, on
(p<0.05), and
(p<0.05. T a b l e
the
2%
in
eriomerus
replicates
average,
and
IX).
3%
5%
fewer
A l l other
significant.
number o f r o c k s
t o two
d i f f e r e n c e between mixed and
tions
that t h i s
i n the
i n s e c t i o n one
two
(Fig.
significantly
IX)
showed t h a t
decreases
In
and
calculated
Clearly,
show t h a t P.
mid-
eriomerus
portions
eriomerus
not
positions.
p a i r e d comparisons t e s t
t h e r e were s l i g h t
(Figs.
hypothesis
l e n g t h s of the
of
highest
run
Table
the
Effects
on
and
14)
over
the
was
and
distribution
in
species
r
14
were
s p e c i e s run
13
uniform
1977
i n a mixed
( F i g . 13,
( F i g . 13,
o t h e r two
a single
f o r higher i n t e r t i d a l
Mixing
i n 1976
in a l l other r e p l i c a t e s .
support
curves
The
was
The
coefficient
experiments
to
one
The
from
evidence
depth
r = +1.00).
data,
+0.630) and
s p e c i e s run
F,H,I) compared
to
s e c t i o n , F i g . 16A-E,G).
a l l
per
single
other
s e c t i o n caused
species
no
distribu-
replicates
(4-5
87
Figure
in
15-
Vertical distribution
1976
the
highest
end
section
one
and
lowest
represent
the
distributions
l i n e s represent
each r e p l i c a t e
single
(days)
of
o f the
by
i n the
species
P.
run
eriomerus i n the
i s represented
runs
by
s e c t i o n f o u r . Dotted
lines
mixed s p e c i e s r u n s ,
solid
distributions.
i s shown on
the
Duration
individual
of
graphs.
89
Figure
in
16.
Vertical
1977.
section
The
one
represent
lines
distribution
highest
and
the
end
represent
each r e p l i c a t e
single
(days)
P.
of the
lowest
distributions
of
by
i n the
eriomerus- i n the
run
i s represented
section
nine.
runs
by
Dotted
lines
mixed s p e c i e s r u n s ,
solid
species distributions.
i s shown on
the
Duration
individual
of
graphs.
90
o
ao
o
'q-
o
o
co
(°/ )
0
o
"T • .
•
o
/fouanb'sjj
o
oo
o
T
o
91
Preference
In
for Vertical location
contrast
strong
t o P.
preference
species
runs.
Spearman
1976:three
single
1977:seven s i n g l e
Tidal
lower
15 and
16
as
and
eriomerus-demonstrated
of
mixed
and
from t h e J " - s h a p e d
n
well
five
as
by
mixed
species
a
single
abundance
twenty-three
coefficients
e i g h t mixed
sig-
(all
positive;
runs,
p<0.05;
s p e c i e s r u n s , p<0.05).
Experiments
R e s u l t s o f the t i d a l
exposure
half
eriomerus
portions
correlation
and
P.
cinctipesP.
T h i s i s apparent
curves i n F i g s .
nificant
for
by
per
o f the
similar
day
experiment
caused
tidal
P.
tank.
increases
( F i g . 17)
e r i o m e r u s t o move i n t o
Control
d u r i n g the f i r s t
and
day.
the
P. e r i o m e r u s t e s t c u r v e s s t e a d i l y
the
fourth
day t h e r e was
suggest that
no o v e r l a p
the
lower
test
curves
After
the f i r s t
dropped
1 h
showed
( F i g . 17).
day,
By
of the ranges f o r the t h r e e
replicates.
These
exposure
results
frequency
compensatory
height.
Table X
+0.9,
Other
+0.6
suggest that
is
and
a
to
summary
o c c u r r e d between
tidal
P. e r i o m e r u s
as an e n v i r o n m e n t a l c l u e
movement i s r e q u i r e d
f r e g u e n c i e s which
1977.
( F i g . 17)
parameters
+0.3
m
levels
1 June
were
to d e t e r m i n e
decrease
of t i d a l
its
exposure
1977
examined
(e.g. t o t a l
utilizes
and
30
for
when
intertidal
ranges
and
September
the
proportion
+1.2,
of
time
ure
1 7 . C r a b s i n t h e upper
were a t o t a l
of t h i r t y
of the t i d a l
tank.
c r a b s i n each treatment.
bars are ranges of three
means.
half
There
Vertical
r e p l i c a t e s , points are the
20 R cinctipes
cu
1
5
t
X
10
<D
Q.
CL
o
o'
control
/ —-
T i m e (d)
94
T a b l e X.
Some t i d a l s t a t i s t i c s , t h e s e were o b t a i n e d f r o m
s t r i p c h a r t r e c o r d i n g s made a t t h e B a m f i e l d t i d e gauge s t a t i o n
between 1 June 1977 and 30 September 1977 (122 d ) . The number
of e x p o s u r e s p e r day r a n g e d f r o m z e r o t o two.
m above
datum
exposure
r a n g e (h)
1.2
0.9
0.6
0.3
exposed
and maximum
parameters
showed
5.8
4.9
4.0
3.2
-
t o t a l number
of exposures
0.5
0.5
0.5
1.2
131
106
42
14
number o f d a i l y
examined,
exposure
exposures) .
the sharpest increase.
sharp
levels
the
is
tidal
tank
environmental
compensatory
In
in
and t h e r e d u c t i o n
test
an
increase
Over
exposure
a 122 d p e r i o d t h e r e
response t o d a i l y
+0.9 m
were
(Table X ) .
f r e g u e n c y between t h e s e two
o f P. e r i o m e r u s i n t h e u p p e r
half
of
( F i g . 17) s u g g e s t t h a t e x p o s u r e f r e g u e n c y
clue
used
movements t o w a r d s
contrast
a l lthe
f r e g u e n c y between +0.6 and +0.9 m
42 e x p o s u r e s a t +0.6 m a n d 106 e x p o s u r e s a t
This
Of
by
this
species
make
lower i n t e r t i d a l l e v e l s .
t o P. e r i o m e r u s , P. c i n c t i p e s
exposure
to
(Fig.
17).
d e m o n s t r a t e d no
95
Discussion
The
run
inhabit
experiments
higher
P. e r i o m e r u s
portions
lowest
data
mixed
lower
for
interactions
magnitude
o f t h e P. c i n c t i p e s
of
of
the
1977
enclosures.
demonstrated
mixed
with
the
P. e r i o m e r u s
population.
P. c i n c t i p e s
enclosures suggests that
this
in
of t h i s
shift
was l e s s
highest
in
lowest,
sections
P. c i n c t i p e s ,
intertidal
P. e r i o m e r u s
of
uses
(Figs
fewer
tidal
demonstrated
15
single
and
mixed
shifted to
runs.
to i t s
The m a g n i t u d e
significant
P. e r i o m e r u s
(p<0.05)
in
frequency
It
the
In contrast to
a preference f o r
and 1 6 ) .
exposure
the
In a d d i t i o n , the
t h e 1976 and 1977 r u n s . .
P. e r i o m e r u s
regions
5%
It i s
determine
P. e r i o m e r u s
species control
or egual to
where
zone.
was s m a l l , b u t s t a t i s t i c a l l y
than
of
s p e c i e s h a s no p r e f e r e n c e
P. c i n c t i p e s ,
single
an
section
p o r t i o n s o f t h e mixed s p e c i e s e n c l o s u r e s compared
distributions
of
(p<0.05)
i t shighest densities.
with
with
(p<0.05) P. c i n c t i p e s i n
including
higher areas i n the i n t e r t i d a l
lower
the
P. c i n c t i p e s -
enclosures,
to
when mixed
e g u a l c h a n c e o f o c c u r r i n g i n any one
distribution
When
and
that
always demonstrated
limit
species
show
species
that
uniform
However,
tended
o f t h e 1976 e n c l o s u r e s and 9% more
also
P. e r i o m e r u s
unlikely
enclosures
i n t h e upper o n e - t h i r d
approximately
the
the
P. c i n c t i p e s
was s m a l l : 1455 f e w e r
section
£• c i n c t i p e s
These
of
that
( F i g s . . 1 3 and 1 4 ) .
t h i s displacement
the
show
is
likely
t o determine
lower
that
when t o
96
move downward
In
but
(Fig,.
c o n c l u s i o n , t h e p r e s e n c e o f P. e r i o m e r u s - h a d
statistically
distribution
fewer
significant
of the higher
P. c i n c t i p e s
species run, there
£•
17 and T a b l e X ) .
eriomerus
spatial
sets
mixed
for
higher
species
intertidal
lower
but s t a t i s t i c a l l y
vertical
distribution
reduced
the proportion
mixed
species
P- e r i o m e r u s
P. c i n c t i p e s ,
the
lowest
data
vertical
Although
which
suggest
by
P. c i n c t i p e s
no p r e f e r e n c e
Also,
in
by t h i s
single
species
I n c o m p a r i s o n , P, c i n c t i p e s - h a d
significant
(p<0.05) e f f e c t
mixing
with
relative
to
the
distribution.
single
In
P. e r i o m e r u s d e m o n s t r a t e d a s t r o n g
portions of the i n t e r t i d a l
zone.
on
the
P. c i n c t i p e s
o f P. e r i o m e r u s i n t h e h i g h e s t
runs
that
o f P. c i n c t i p e s .
o f P. e r i o m e r u s ;
control
the
P. c i n c t i p e s .
limit
runs suggest
a small,
the
in
demonstrated
levels.
on
small,
i n t h e l o w e r p o r t i o n o f t h e mixed
a r e no t r e n d s
distributions
and
species,
occurred
the
effect
a
parts of
species
contrast
to
preference f o r
97
GENERAL DISCUSSION
Density and V e r t i c a l D i s t r i b u t i o n of the-P. eriomerus
PQ£JJ l a t i on
The run experiments
behavior
determines
(summarized
the
position
in
of
F i g . 18)
that
the upper l i m i t of the
P. eriomerus p o p u l a t i o n i n the i n t e r t i d a l zone.
eriomerus
show
Petrolisthes
has a strong preference f o r the low i n t e r t i d a l
zone.
Furthermore, the v e r t i c a l d i s t r i b u t i o n of the experimental popu l a t i o n i n the runs i n 1977 i s s i m i l a r t o that o f
the
natural
p o p u l a t i o n estimated from t r a p data ( F i g . 18).
The
a d a p t i v e importance of a v o i d i n g the higher i n t e r t i d a l
zone i s t h a t i t maintains P. eriomerus below i n t e r t i d a l
which
were
(Fig.
4) .
varied
found
The upper
little
position
to
be
s t r e s s f u l or l e t h a l to t h i s
limit
during
the
of
course
i n d i v i d u a l s ranging up t o +0.9
at
the
m.
(Fig. 4).
as
has
population
t h i s study.
The mean
m (Table I ) , with
the
as 0.3
transplant
m above the +0.9
I t seems u n l i k e l y t h a t the upper
m o r t a l i t i e s when warm
(Connell
of
R e s u l t s of
P. eriomerus p o p u l a t i o n would
coincide
P. eriomerus
species
show that t h i s s p e c i e s i s unable t o s u r v i v e
i n t e r t i d a l h e i g h t s as l i t t l e
level
the
of t h i s l i m i t was approximately +0.8
experiments c l e a r l y
levels
weather,
been
1961a, F o s t e r
1971a).
portion
of
be s u b j e c t e d t o c a t a s t r o p h i c
calm
suggested
m tide
seas
for
Unlike
and
spring
barnacle
tides
populations
barnacles,
however,
98
Figure
18. Summary
and
runs.
each
of the d i s t r i b u t i o n s
of crabs i n the traps
P o i n t s r e p r e s e n t t h e mean f r e q u e n c y
level
for a l l replicates.
mean f r e q u e n c y
o f P. c i n c t i p e s
Dotted
lines
of crabs at
represent the
which e n t e r e d a t e a c h o f
t h e f o u r t r a p l e v e l s i n 1975 and 1977. Dashed
represent
entered
Solid
in
and
t h e mean f r e q u e n c y
a t each
lines
of the four trap l e v e l s
r e p r e s e n t t h e mean f r e g u e n c y
t h e t h e combined
single
aproximately
and 10% r e s p e c t i v e l y
i n 1975 a n d 1977.
o f P.
eriomerus
i n 1976
o f P. c i n c t i p e s - a r e n o t
b u t t h e 1975 and 1977 c u r v e s
horizontal
which
and mixed s p e c i e s r u n s
1977. The r u n d i s t r i b u t i o n s
shown h e r e ,
25%
o f P. e r i o m e r u s
lines
would be
and h a v e Y - i n t e r c e p t s a t a b o u t
(see T a b l e I X ) .
Position of Run S e c t i o n s
Depth (Meters above
Datum)
CD
100
porcelain
crabs
advanced
sensory
demonstrated
personal
that
incessant
substrata
eriomerus
(especially
occurs
during
s e l e c t i o n f o r an
Vertical
position
exposure
the
upper
Results
of
respond
into
limit
tidal
to
areas
upper
limit
dynamic
P.
not
the
P.
equilibrium
only
one
levels.
effect
levels,
The
and
run
when
intertidal
to
height.
clue,
that
by
ability
below
(Table
P.
X).
eriomerus
moving
I
down
did
not
exposure
I believe that
i s the
of
to p o t e n t i a l l y
result
e q u i l i b r i u m was
of
the
a
i n d i v i d u a l s to
stressful
movinq t o l o w e r
16 and
a
tidal
i n frequency
(Fig,. .17).
( F i g s . 15,
exposed
reasonable
exposures
involved.
the
of compensation a f t e r the
that
i t i s possible that
t o compensate by
experiments
assume
population
eriomerus population
between
that
i n d i v i d u a l s of
such
suggest
exposed
d e t e r m i n e when t h e y have wandered
lethal
One
duration
newly
individual detecting
eriomerus
p a r a m e t e r s and
not
of the
clue.
short
were
tidal
is
the
The
suggests
we
lethal
to assess
experiments
frequent,
examine o t h e r
frequency
the
tank
which
If
are
by
1972,
adaptive
invade
II) ,
showed a marked i n c r e a s e
of
The
i t would seem
i s determined
frequency,
(Molenock
submergence p l a c e s
ability
environmental
Petrolisthes
readily
Table
which
relatively
however, i s unknown.
nature.
spring tides),
postulate
nonstressful
in
levels
behavior
species
and
of
possess
experiments).
both
periods
at
and
importantly,
behavior,
( F i g . .2
behavior
exploration during
More
from a r e n a
i n d i v i d u a l s of
exploratory
motile
exploratory
of exploratory
available
P.
highly
systems.
observation
importance
fact
are
18)
or
intertidal
showed
perturbed.
the
101
Some
factors
limpet
which
P. e r i o m e r u s .
species
demonstrate
are
similar
For
example,
to
permitted,
summer months
However,
limpets
to
desiccation.
strongly
this
are
excursions
populations
is
filter
conditions
(Table
by d e a t h
my
explanation
observations
I
conclude
means
forthis
the
intertidal
higher
that
both
u n n e c e s s a r y a s compared t o a
scavenging
permit
of
(Frank
productus)
or
1965, B r a n c h
P. e r i o m e r u s
they
settle
o f t h e upper l i m i t
reason
that
foraging
t o use s i t e - s p e c i f i c
The
from
that
(e.g. Cancer
that
of
o f t h e P. e r i o m e r u s
I).
which
p o r t i o n s o f the i n t e r t i d a l
difficult
within
was c a u s e d
shift
i n large part, to the fact
feeders,
juveniles
+0.6 m, s u g g e s t i n g
is
stable
due,
population
limit
hot dry
1972, B r a n c h 1975,
populations,
upper
winter
during
some
w h i c h move i n t o more f a v o r a b l e g r a z i n g
Small
lowest
the
summer
areas
limpet
that
crab
the
intertidal
are probably
brachyuran
seasonal
of
i s temporally
stability
species
1965, Breen
Unlike
suggest
population
1954, F r a n k
by
of limpets
r a n g e s when c o o l , m o i s t
t o lower l e v e l s
part
lower
demonstrated
retreating
(Lewis
1976).
those
to physical
numerous p o p u l a t i o n s
have been shown t o expand t h e i r
weather
responses
from
zone
were
the
areas
when
1975, 1976).
found only
plankton
(Fig, 3).
settlement
limpet
as
below
i n the
However, i t
an
sufficient
o f t h e P. e r i o m e r u s
population.
i s t h a t megalopa may e i t h e r be s p e c i f i c f o r
r a n g e i n t o which t h e y
intertidal
settle,
or they
may
settle
r a n g e s and move t o l o w e r l e v e l s
within
102
a short
time p e r i o d ,
factors
in
or
higher
possibilities
£*
is
dominant
l o w e r d e n s i t i e s of
the
mixed
out
this
shift
with
P.
i n the
was
P.
compared
sessile
are
caused
largely
been
invertebrate
extent,
limit
t o an
intertidal
of t h e
higher
limits
the
However,
as
magnitude
of
that
competition
distribution
marine
studies
P.
By
the
this
environment
process
and,
is a
with
of h a b i t a t
upper
on
to
cinctipes,
proximate
eriomerus population
(Connell
conducted
factors
with
regions.
intertidal
physical factors
Physical
But,
abundance
intertidal
of
of
i n t e r f e r e n c e from
f a c t o r s which determine the
P.
suggesting
portion
16).
f o r low
interactions
i n c r e a s i n g l y harsh
height.
that
i t s vertical
from
eriomerus population.
response
ultimate
over
derived
of the
upper
showed
i n i n f l u e n c i n g the
by
the
the
VIII)
f o r space,
and
directly
species.
biotic
site-specific
adult
suggesting
upper
probably
P.
15
preference
prevaling idea that
has
lesser
Figs.
minor r o l e
species
intervals
mobile
were c a u s e d by
(Table I X ) ,
a
two
highly
(Table
eriomerus i n the
eriomerus population
populations
1972)
small
to t h i s
The
and
latter
2 wk
Also,
d i s c u s s i o n o f C h a p t e r IV,
c i n c t i p e s has
the
w i t h i n the
competitor
enclosures
c i n c t i p e s ( T a b l e IX
pointed
of
species
P.
the
physical
datum.
arena experiments
a
harsh
event
( F i g . 3).
m above
that
P,
to occur
i n 1975
0.9
of the
cinctipes
any
by
t o e x p l a i n what k e e p s t h e
P . . e r i o m e r u s below
Results
killed
In
would have had
fails
are
areas.
between o b s e r v a t i o n s
settlement
they
a
are
limit
cause
of
behavioral
increasing
selection,
103
P.
its
eriomerus
The
survive
site
agree
with
physical
below
and
reproduce
f a c t o r s do
Since
the
early
evidence
has
c a u s e d by
biotic
Petrolisthes
intertidal
show t h a t
that
this
P.
studies
not
prevent i n t e r t i d a l
Paine
1974,
1960s
(Connell
shift
very
eriomerus i s
range of the
however,
to
explanantion
(Table
I)..
settlement
settled
P.
use
o f the
The
fails
lower l i m i t
reason
to explain
for
shown
from
able
m
and
are
population.
the
low
However,
the
seems
exclude
only
within
the
is
difficult,
a
sufficient
cinctipes
population
i s that
what l i m i t s
predation.
I).
It
settlement
this
or
competitively
P.
1953,
lower l i m i t s
i t , therefore,
(Table
the
living
of
c i n c t i p e s from
to
that
Powell
Table IX).
small
of
data
deal
competition
and
site-specific
These
1978).
c i n c t i p e s - were f o u n d
conspecific adult
Diana
have
species
able
the
1961a,b), a g r e a t
some P.
14
of
IV).
which s u g g e s t s t h a t
13,
was
cinctipes i s
( B a r n e s and
Suchanek
stresses, typically
(Figs
P.
which
limit
c i n c t i p e s f r o m l e v e l s below +0.6
Recently
at
Population
Table
other
eriomerus displaced
magnitude of
factors
lower l i m i t
of
accumulated
zone
physical
cinctipes
below t h e
lower d i s t r i b u t i o n a l
1961b, 1972,
unlikely
P.
d i s t r i b u t i o n ( F i g . 4 and
the
Connell
of t h e
data c l e a r l y
those
by
limit.
Lower L i m i t
transplant
Island
P.
direct limitation
upper i n t e r t i d a l
The
to
avoids
the
as
that
highly
site-specific
mobile
adult
104
R-
cinctipes to levels
are
able
In
R-
to l i v e
w e l l below t h i s h e i g h t
c i n c t i p e s from
Some
i n h a b i t i n g the
competition
c i n c t i p e s from the
of
this
that
low
displacement
i t caused
preference
though
population
the
of t h e
factors
R-
P.
were
of
this
was
seem
areas
of
and
zone, b u t ,
there
for
higher
density
was
population
for
they
the
prevent
intertidal
displace a
the
P.
intertidal
few
magnitude
cinctipes
has
regions,
even
g r e a t e s t above t h e
upper
( F i g . 18).
setting
were
to
were no i n d i c a t i o n s
I t i s u n l i k e l y that
responsible
study.
not
P-. e r i o m e r u s may
small
they
(Fig.. . 4 ) .
lowest
intertidal
eriomerus
cinctipes population,
course
with
zonation.
a behavioral
limit
m a b o v e datum e v e n t h o u g h
c o n c l u s i o n , p h y s i c a l f a c t o r s do
zone.
P.
above 0.6
not
lower
If
limit
apparent
biotic
of
the
during
the
105
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