August, 1979 the Thesis of John Grenfell Is Approved

California State University, Northridge

Ecological Aspects of Feeding Behavior of Some Tellinaceans \l (Mollusca: Bivalvia)

A thesis submitted in partial satisfaction of the requirements for the degree of ~~ster of Science in

Biology

John Kemp Grenfell

August, 1979 The Thesis of John Grenfell is approved:

Earl Segal

committee chairman

California State University, Northridge

ii ACKNOWLEDGEMENTS

I would like to thank Ross Pohlo, the chairman of my

oommi ttee, for his help and valuable criticisms of the ini tlal

thesis drafts.

I am also indebted to Earl Segal and Tony Gaudin for

their helpful criticism and advice.

I would also like to thank my wife, Carol, without whose help tr~s project would not have been completed.

iii TABLE OF CONTENTS

Page

ACKNOWLEDGEHENTS • • • • • • • • • • • • • • • • • • • • • • • iii

LIST OF TA.BLJ

INTRODUCTION • • • • • • • • • • • • • • • • • • • • • • • 1 JifA. T.ERIALS AND METHODS • • • • • • • • • • • • • • • • • • • • • 4

Areas of Study • • • • • • • • • • • • • • • • • • • o • 4 Sampling Technique • • • • • • • • • • • • • • • • • • • • 16 Substrate Analyses • • • • • • • • • • • • • • • • • • • • 16 Shell Measurement • • • • • • • • • • • • • • • • • • • • • 19 Mantle Cavity and Stomach Contents • • • • • • • • • • • • 19 Feeding Behavior • • • • • • • • • • • • • • • • • • • • • 19 Statistical Analyses • • • • • • • • • • • • • • • • • • • 19

RESULTS • • • • • • • • • • • • • • • • • • • • • • • 21 Mantle Cavity and Stomach Contents •••••••••••• 21 Behavior of the Inhalent Siphon • • • • • • • • • • • • • • 21 Population Density •••••••••••••••••••• 25 Shell Size • • • • • • • • • • • • • • • • • • • • • • • 29 Substrate Analyses • • • • • • • • • • • • • • • • • • • • 31

DISCUSSION • • • • • • • • • • • • • • • • • • • • • • • 34 Feeding Behavi.or • • • • • • • • • • • • • • • • • • • • • 34 Population Density • • • • • • • • • • • • • • • • • • • • 37 Substrate Analyses • • • • • • • . -· • • • • • • • • • • • 38 Shell Size • • • • • • • • • • • • • • • • • • • • • • • 38 LITERA1URE CITED • • • • • • • • • • • • • • • • • • • • • • • 40 APPENDICES Appendix 1 Dimensions for ~~coma nasuta collected from Mugu Lagoon • • • • • • • • • • • • • • 42

Appendix 2 Dimensions for ~anguinolaria nuttallii collected from Mugu Lagoon • • • • • • • • • 42

iv TABLE OF CONTEN'lli cont. Page Appendix 3 Dimensions for Tagelus californianus and Macoma nasuta collected from Edison Canal • • 43 Appendix 4 Dimensions for Tagelus californianus collected at Back-Bay Newport • • • • • • • • 44 Appendix 5 Dimensions for Macoma secta and Sanguinolaria nuttallii collected from Lower Newport Bay • • • • • • • • • • • 0 • • 45

Appendix 6 Dimensions for ~~coma nasuta, Macoma secta and Florimetis obes~ollected at NewPort Bay-:-. • • • • • • • • • • • • • • • 46

Appendix 7 Regression analyses for Tagelu~ californianus • • • • • • • • • • • • • • • • 47

Appendix 8 Regression analyses for Sa~nol~~ nuttallii • • • • • • • • • • • • • • • • • • 48 Appendix 9 Regression analyses for Macoma nasuta • • • • 49

Appendix 10 Regression analyses for Florimetis obesa • • 50

Appendix 11 Regression analyses for Macoma ~ • • • • 51

v LIST OF TABLES

Table Page

1 Stomach contents, siphonal behavior, and feeding type • • • • • • • • • • • • • • 0 • • • • • • • • 22

2 Mean number and t-values for species collected allopatrically and sympatrically per 0.5 m2 ••••••• 26

3 Mean number and t-values for allopatric populations and total number of tellinaceans in sympatric communities per 0.5 m2 •••••••••••••••••• 28

4 Mean length and height and t-values for allopatric and sympatric species •••• • • • • • • ••• 30 5 Slopes of regression lines and t-values comparing the slopes of those lines • • • • • • • • • • • • • • •• 32 6 Sediment size distribution and organic carbon content from the areas of study, percent by weight •••••••• 33

vi LIST OF FIGURES

Figures Page

1 Locations of tellinaceans and nature of occurrence • • • 7

2 Morro Bay • • • • • • • • • • • • • • • • • • • • • • • 9

3 Edison Canal • • • • • • • • • • • • •••••••••• 11

4 Mugu Lagoon • • • • • • • • • • • • • • • • • • • • • • 13

5 Newport Bay . . ~ . . . . ·- . . . . • • • • • • • • • • 15 6 Types of inhalent siphonal behavior • • • • • • • • • • 24 ~

vii LIST OF PLATES

Plate Page

1 Species studied. • • • • • • • • • • • • • • • • • • • • 6

A. Macoma nasuta B. Tagelus californianus c. Macoma secta D. Flarimetis obesa E. Sanguinolari~ nuttallii

2 The quadrat sampler and sieve • • • • • • • • • • • • • 18

viii ABS'ffiACT Ecological Aspects of Feeding Behavior of Some Tellinaceans

(Mollusca: Bivalvia)

John Kemp Grenfell

Master of Science in Biology

August, 1979

The feeding behavior of five species of tellinaceans was studied in four locations in California, USA. The organisms were studied in areas where they occurred sympatrically with other tellinaceans and in other areas where no other tellinaceans ¥tere present., Random samples v1ere taken to determine population densities.

Shell sizes were measured to determine if there was any difference due to competition. Each population was examined to ascertain the type of feeding behavior. Feeding behavior was determined from the stomach contents and from the behavior of the inhalent siphon.

It was observed that when closely related species occur in the same location they exploit different microhabitats. Some organisms use suspended material as their primary food source, while others ingest deposits. Macoma nasuta is a deposit feeder when not in competition with other tellinaceans, but fed on both deposits and

ix - ~ ------

suspended material when coexisting with other deposit feeding

Tellinacea. There is not any significant change in the population denslty or shell size which can be attributed to differences in feeding behavior. Growth of tellinacean species was the same in different geographical locations.

X INTRODUC'llJ:ON

The superfamily Tellinacea is a gToup of burrowing bivalves found on the Pacific Coast of North America from Alaska to Panama.

Five species within this superfamily were studied. Macoma nasuta (Conrad, 1837) is usually found in quiet waters with muddy substratum about 15 em below the surface, rangi-ng from Alaska to Baja California, Mexico (Abbott, 1954). Macoma secta (Conrad, 1837) is found in bays 15 to 20 em below the surface from Vancouver Island to the Gulf of California (Abbott, 1954). Sanguinolaria nuttallii Conrad, 1837 can be located in estuaries 15 to 25 em oelow the surface from Monterey, California to Baja California (Abbott, 1954). Tagelus californianus (Conrad, 1837) is found on muddy sand flats 15 to 30 em below the surface, from Humboldt Bay, California to Panama (Abbott,

1954). Floriroetis obesa (Deshayes, 1855) is found in clean sand about 15 to 25 em below the surface, from Point Conception, California to Magdalena Bay, Baja California (McLean, 1969). According to Yonge (1949) all Tellinacea are deposit feeders. More recently Bradfield and Newell (1961), Holme (1961), Purchon (1963), Wade (1965), Pohlo (1966, 1967, 1969, 1972, 1973), Mauer (1967), .and Reid and Reid (1969) showed some members of the Tellinacea are suspension feeders. Both Macoma nasuta and Macoma secta are considered to be deposit feeders, while Taeelus califorruanus and

Sanguinolaria nuttallii are considered to be suspension feeders

(Pohlo, 1969, 1972, 1973). However Florimetis obesa may function as both a suspension and deposit feeder (Pohlo, 1973).

1 ,.., .::.

In suspension feeders, the animal holds the inhalent siphon at or near the surface often in a conical depression and at times extends it several centimeters above the substratum. At no time, however, is the siphon seen actively inhaling the deposits. The stomach contents reflect the siphonal behavior. Sand grains and nutrient particles in the stomach are small, averaging 50 fl• Nutrients are composed of bacteria, flagellates, small dinoflagellates, diatoms and debris (Reid and Reid, 1969). In deposit feeders, the inhalent siphon rests on the substratum, moving aro1tnd continuously, periodically pressing its aperture down on the sand inhaling small amounts of the surface matter (Yonge, 1949, and Reid and Reid, 1969). Stomach contents consist of surface diatoms, debris, and bacterial colonies living on large sand grains (Reid and

Reid, 1969). In this study allopatric refers to the presence of only one tellinacean species, while sympatric refers to the coexistence of two or more tellinaceans. 'l'ellinacean species have been observed coexisting (Pohle, personal communication). If the sympatric species are all deposit or all suspension feeders, does this constitute niche overlap? Pianka (1978) maintains that, "niche overlap occurs when two organismic units use the same resources or other environmental variables.". If resources are not in short supply it is possible that two species may coexist, using the same resource. Hutchinson (1957) proposed that a species population could be described or characterized by its position along several dimensions, such as temperature, prey size and food source. He treated niche overlap in a simple way: he 3

made the assumption that the environment was saturated and that

competition and exclusion must occur. The Gause (1934) principle

states that species cannot coexist for long if they use the same resources. If the resources available are in short supply and niche

overlap does occur there must be competition. It may cause character

displacement, referring to morphological differences between indivi-

duals of· an allopatric species and individuals of that same species occurring sympatrically. Coexisting organisms may pa.rti tion resources in different ways; the time and place of resource utilization as well as the size of the resource would be important in the segregation of habitat.

The purpose of this study is to answer the following questions:

1. What is the food source of the allopatric species? 2. Is the food source changed when these species occur sympatrically? 3. Do allopatric species change feeding behavior \vhen coexisting with other tellinaceans? 4. Is there a density difference when comparing two populations of the same species, one or which is sympatric and the other allopatric? 5. Is there any character displacement as inter- preted by shell size differences? 6. Do sympatric and allopatric populations have different sediment preferences? {' '

MATERIALS AND METHODS

J\..reas of Stud,;r

Collections were made at four locations on the California coast, USA. All species used in the study are shown in Plate 1 and their distribution is shown in Figure 1.

Morro Bay is adjacent to the city of Morro Bay in San Luis

Obispo County. Collections were made in the upper reaches of the bay about 1.5 km from the entrance channel on sand-mud flats (Fig. 2).

Edison Canal, in Ventura County, is a hot water effluent channel connecting the Southern California Edison generating facility at

Mandalay Bay with the Channel Islands Harina near Oxnard Beach.

Collections were made along the c~l which is 50 m wide and 2 km long. The banks of the canal are steep and consist of black sand-mud with plant detritus present (Fig. 3). Mugu Lagoon is si tu.ated on Point I>1ugu Naval Base in Ventura County (Fig. 4). The Lagoon is divided into three parts, the western arm, main basin, and the eastern arm. Collections were made along the barnes of subtidal channels and on intertidal sand and mud flats in the eastern arm approximately 1 km from the entrance channel.

Newport Bay is located south of the City of Newport Beach in Orange County (Fig. 5). The bay is divided into Upper or Back-Bay Newport and Lower Newport Bay with the dividing point being the

Pacific Coast Highway. Back-Bay Newport has topographic character istics similar to Mugu Lagoon. Collections were made on mud flats approximately 4 km from the entrance channel& In Lower Newport Bay collect~ons were made at a small protected sand beach 400 m north of

4 5

Plate 1: Species studied

A. Macoma nasuta B. 'I'a&elus californianus C. Macoma secta D. Florimetis obesa E. p~ngu.inolaria nuttallii

Figure 1

Locations of tellinaceans and nature of occurrence

nature of location tellinaceans occurrence

allopatric Mugu Lagoon ...... Macoma -· nasuta Sanguinolari~ nuttallii allopatric

Edison Canal Macoma nasuta -·----- allopatric Macoma nasuta sympatric Tazelus califo~

Newport Bay Back-Bay Tagel~s californianus allopatric

Lower Newport Bay Macoma secta allopatric

Macoma secta ------· sympa. tric ~an~nolaria nuttallii ~

Morro Bay Florimetis obesa allopatric

Macoma secta sympatric

Macoma nasuta 8

Figure 2: Morro Bay, San Luis Obispo County, California; 3~22 1 N Latitude, 120°51' W Longitude.

Collection site designated by X. 9

City of Morro Bay

:.~ t .• North ,, \ • • Morro Bay

•• .. ••• ..• ., . . ",. ., .... '•' " ., ~ ., state . park Pacific Ocean ·' . • sand ...·-dunes .. . X .. ' collection .. ~. . site • • .. .. •• • •• mud flats •• ...... '· \ 1 km ...... 10

Figure 3: Edison Canal, Ventura County, California; 34" 07' N Latitude, 119" 07' W Longitude. Collection site is designated by X. Southern California Edison ~~----Mandalay Bay Generating Station 1 North

\-lest Fifth St~

collection site

Edison Canal

I 1 Oxnard Beach lkm 12

Figure 4: Mugu Lagoon, Ventura County, California; 34'" 30 1 N Latitude, 119" 24 1 W Longitude. · Collection sites designated in the eastern arm by X' s. !'("'\.-

l Naval Reservation Boundary North Calleguas Creek Pacific Coast Highway ._ ..

\ 1 ~ \

collection sites

Entrance Channel

Laguna Point Eastern arm Pacific Ocean 14

Fi~e 5: Newport Bay, Orange County, California; 33'37' N Latitude, 117°52' N Longitude. Collection sites designated by X's. 15

City of Ne1t:port Beach

North

Pacific Coast Highway

Pacific Ocean

l.km 16

the entrance channel.

Sampling Techniq~e

In each of the study areas a population of organisms was located by digging at random in the substratum. Using this site as the center, an area was staked out which was 10 meters on a side.

The sample area was divided into 100 one meter square quadrats, four of which by random number table were chosen for study (Sokal and Rohlf, 1969). The density of each species was then esti,,iated 2 by the number of individuals found in a 0.5 m area. All collections were made during tides lower than- 0.15 meters. 2 The sampling frame (Plate 2) is 0.5 m and 20 em deep. It was constructed using cedar 5 em by 2 em and galvanized sheet metal 2 1.5 mm thick. The sieve is 0.5 m and is made from 5 em by 2 em c~dar and. wire mesh which had 6 openings per em.

The sampling frame was placed on the substratum and the wooden edges pressed down until the top of the apparatus was flush with the surface. The substratum and all organisms entrapped were then re moved with shovels and hand scooping tools and washed through the sieve. All organisms greater than 1 em long were retained for examination. From every sample four individuals of each tellinacean species present were opened and preserved in alcohol for later examination of the stomach and mantle cavity. A substratum sample was also taken and placed in a 175 m1 jar for sediment examination.

Substrate Analyses

The procedures used for the substrate analyses of particle size distribution and organic carbon content are described by 17

Plate 2: The quadrat sampler and sieve. The sampler and sieve both are 0.5 meters square.

Carver (1971). The sizes of u.s. standard sieves used were as follows: 2000 p (very coarse sand), 1000 p (coarse sand), 500 p..

(medium sand), 250 ~(fine sand), 125 ~ (very fine sand), and 62 ~

(silt and/ or clay). Any material smaller than 62 ~was considered collectively as the silt-clay fraction. The procedures for deter mining organic carbon content gives an approximate val11e.

~1 Measurement

Length (greatest anterior-posterior distance) and height

(greatest distance from the umbo to the central margin of the shell) measurements were obtained using Vernier Calipers with an accuracy of 0.01 em (appendices 1 to 6).

Mantle Cavi~l ~nd Stomach Contents

Animals used for mantle cavity analyses were preserved in the field and taken to.the laboratory. In the laboratory the mantle cavity was examined, the stomach was opened and the contents were observed through a dissecting microscope.

Feeding Beh~

The position and movement of the inhalent siphons were observed in place in the field using an underwater viewer. At each collection site 20 to 30 organisms were observed. -Individuals (2 to 20) were also placed in a plastic bucket with substratum at the site of collection and their siphonal behavior was observed. Time (25 to

30 minutes) was allowed to pass so that the individuals recovered from handling trauma after transfer to the bucket.

§tatistical Analyses

I used t-tests at the 0.05% level of significance to determine 20

differences between the number of allopatric individuals and the number of individuals of that same species in a sympatric community.

Also they were used to compare allopatric population densities and densities of all tellinaceans in a sympatric community. A regression analysis was used to estimate the relationship between shell length and shell height. The slope of the regression line was calculated using a method described by Sakal and Rohlf (1969). The regression lines for different populations of the same species were then com pared using a different t-test shown by Simpson ( 1960). RESUL~

,!:!antle Cavity and Stomach Contents

Stomach contents of all the species studied and the areas in which they were collected are shown in Table 1.

In Macoma nasuta from Mugu Lagoon the mantle cavity had very fine sand grains and debris, mostly on the demibranchs and labial palps. ~ nasuta from Edison Canal (both allopatric and sympatric) had black debris in the mantle cavity and adhered to the palps.

M. nasuta collected from Morro Bay had small amounts of fine sand in the mantle cavity and on the foot.

_§a!!gqinolaria nuttallii from Nugu Lagoon and Lower Newport

Bay had small amounts of very fine sand in the mantle cavity near the area of pseudofeces accumulation.

Tagelus californianus collected from Back-Bay Newport and

Edison Canal had no sand or clay in the mantle cavity. There were small pieces of organic matter adhered to the foot and palps.

Macoma secta from Lower Newport Bay (both allopatric and sympatric) and :f-1orro Bay had the entire mantle cavity filled with medium size sand grains, organic matter and debris.

Florimetis obesa from Morro Bay (both allopatric and sympatric) had a large amount of fine sand in the mantle cavity, 'vi th algae, diatoms, f"lagellates, and debris mixed in.

Behavior of the Inhalent Siphon The types of inhalent siphon behavior for all organisms are shown in Figure 6. The inhalent siphon of Macoma nasuta at Mugu

Lagoon and Edison Canal (both allopatric and sympatric) extended

21 Table 1. Stomach contents, siphonal behavior, and feeding type allo~tric species stomach contents siphonaJ., beha,v:i.or ______-~fe_~

Sanguinolaria nuttallii Nugu Lagoon very fine sand, diatoms, inactive, vertical suspension organic matter

Florimetis obesa Norro Bay, yery fine sand, algae diatoms, inactive, vertical both deposit flagellates, debris and suspension Tagelus californianus Back-Bay Newport very fine sand, clay active, not suspension organic matter inhaling substrate Macoma secta Lower Newport Bay Medium, organic matter active, taking in deposit debris substrate

1\) 1\) Table 1 cont.

SY!!\l)atric species stomach contents si;phonal behavior feeding t:y,:ee Edison Canal Hacoma nasuta silt, diatoms, debris active, inhaling deposit substrate

T_§£elus californianus very fine sand, silt, debris active, aperture up suspension

Morro :Bay Macoma secta medium sand, organic matter, active, inhaling deposit flagellates, debris substrate

Macoma nasuta small amount of sand, active, aperture up both suspension green algae, debris not taking in substrate and deposit

Florimetis obsea fine sand, organic matter, inactive, vertical both suspension flagellates, debris and deposit

Newport :Bay Lower Newport Bay Macoma secta medium and fine sand, active, inhaling deposit organic matter, diatoms, substrate debris Sanguinola.ria nuttallii small amounts of very inactive, vertical suspension fine sand, diatoms , flagellates

1\) \.>1 24

Figure 6 Types of inhalent siphonal behavior

~anguinolaria nuttallii

suspension deposit Macoma nasuta

Tagelus californianus

•

Macoma secta

Florimetis obesa 25

out horizontal to the substratum and lay on it. The siphon moved around with the aperture pressed to the surface inhaling material.

Tagelus californianus observed at Back-Bay Newport had a very active inhalent siphon. The siphon emerged and was held parallel to the substratum with the opening held upward. The animals were not observed ingesting deposits.

The inhalent siphon of Florimetis obesa observed at Morro Bay

(both allopatric and sympatric) was held 1 to 2 em above the sub stratum in a vertical position. It did not appear to actively inhale deposits from the substratum. However, it was observed that the substratum was ingested because of the proximity of the siphon opening to the surface.

The long inhalent siphon of ~mcoma secta· observed at Lower

Newport Bay (both allopatric and sympatric) extended and lay on the substratum. It moved around continuously and would press its aperture down on to the sand and surface material was drawn in.

Siphonal activity for each species in a sympatric community was the same as for that species in an allopatric population, except for ~~ nasuta at Morro Bay. The siphon lay on the substratum with the aperture held upward. Stomach contents indicate that deposits were ingested. However, the organisms were never observed with their siphons pressed to the substratum actively inhaling material.

Popu1ation Densitx

The mean number of individuals sampled allopatrically ~~1d sympatrically are shown in Table 2. The largest population censity was found in Back-Bay Newport, where T~elus californianus !1~i a 26

Table 2. Mean number and t-values for species collected allopatrically and sympatrically per 0.5 m2.

mean range s.d. t-values Macoma nasuta Mugu Lagoon a 12.25 8-17 3-77 vs. 1. 727 6** Edison Canal s 7.50 6-10 4.00

Mugu Lagoon a 12.25 8-17 3.77 vs. 2. 718'6* Morro Bay s 7.00 6-9 0.82

Edison Canal a 11.25 8-14 2.50 vs. 1.566 Edison Canal s 7.50 6-10 4.00

Edison Canal a 11.25 8-17 3-77 vs. 3.236* Morro Bay s 7.00 6-9 0.82 Macoma secta

Lower Newport Bay a 5.50 3-8 2.08 vs. 0.7866 Morro Bay B 4.25 4-5 2.41

Lower Newport Bay a 5.50 3-8 2.08 vs. 0.326 Lower Newport Bay s 5.00 4-6 0.82 Tagelus californianus

Back-Bay Newport a 26.0 17-32 6.0) vs. 6.1876* Edison Canal s 5.0 1-10 3.05

Sangpniolar~ nuttallii

Mugu Lagoon a 18.5 1&:19 1.28 vs. 7.3956* Lower Newport Bay s 5.75 4-6 3.20 Florimetis obesa

Morro Bay a 5.00 4-6 0.82 vs. 0.5226 Morro Bay s 4.75 4-5 0.50 ** subscripts indicate degrees of freedom a allopatric population * signi!'icant difference at 0.05 level s sympatric community 27

2 mean number of 26 individuals 0.5 m • Sanguinolaria nuttallii from Mugu Lagoon also had a large population density with a mean of 18/0.5 2 m • The two allopatric populations of ~acoma nasuta were similar. 2 The population in Mugu Lagoon had a mean density of' 12.25/0.5 m 2 and at ~dison Canal the mean density was 11.25;0.5 m • All other populations were lower in mean density having fewer than seven individuals per 0.5 m2 • Means of allopatric populations are compared with the means of the same species in sympatric communities (Table 2). There are significant differences in density between allopatric and sympatric populations of the same species. The Sanguinolaria nuttallii population from Mugu Lagoon was significantly larger than the ~ nuttallii population at Lower Newport Bay. Tagelus californianus found alone at Back-Bay Newport has a significantly larger population than the one in Edison Canal (sympatric). The population density of Macoma nasuta in Mugu Lagoon (allopatric) and in Edison Canal

{allopatric) were significantly larger than its sympatric population in Morro Bay.

The mean number of individuals in the allopatric population was also compared to the mean of all te~linaceans found in the areas of sympatry. The results are listed in Table 3. There was only one instance where there were more clams in an allopatric population than in a sympatric community. This occurred in a population of Tagelus californianus in Back-Bay Newport that was significantly larger than a combined population of T. californianus and Macoma nasuta at Edison

Canal. There were three cases in which the allopatric population 28

Table 3 .. Mean number and t-values for allopatric populations and total number of tellinaceans in sympatric communities per 0.5 m2. Macoma nasuta mean range s.d. t-values Mugu Lagoon a 12.25 8-17 3.77 vs. 0.086** Edison Canal s 12.5 7-20 5.44 Mugu Lagoon a 12.25 8-17 3.77 vs. 1.956 Morro Bay s 16.0 14-19 0.74 Edison Canal a 11.25 8-14 2.50 vs. 0.486 Edison Canal s 12.5 7-20 5.44 Edison Canal a 11.25 8-14 2.50 vs. 3.656* Morro Bay s 16.0 14-19 0.74 Macoma secta

Lower Newport Bay a 5.50 3-8 2.08 vs. 9.636* Morro Bay s 16.0 14-19 0.74

Lower Newport Bay a 5.50 3-8 2.08 vs. 4.526* Lower Newport Bay s 10.75 5-13 }.95 Tagelus californiam1s

Back-Bay Newport a 26.o 17-32 6.05 vs. 3-336* Edison Canal s 12.5 7-20 5.44

S~nguinolaria nuttallii

Mugu Lagoon a 18.5 16=19 1.28 vs. 1.676 Lower Newport Bay s 10.75 5-13 3.94 Florimetis obesa

Morro Bay a 5.00 4-6 0.83 vs. 24.566* Morro Bay s 16.0 14-19 0.74 ** subscripts indicate degrees of freedom a allopatric population * significant difference at 0.05 level s sympatric community 29

was smaller than the sympatric population. M. nasuta from Edison Canal

(allopatric) was smaller than the coexisting populations of M. nasuta,

~ sect~, .and Florimetis obesa from Morro Bay. The allopatric populations of both F. obesa and~ secta were both significantly less dense than their respective sympa tric communi ties. However, allopatric populations of San£Uinolaria nuttallii and M. nasuta were net different when compared with the total tellinaceans in their respective sympatric communi ties.

Shell Size

The mean values for shell length and height of allopatric and sympatric species and the t-values comparing length and height are shown in Table 4. Allopatric populations of Sanguinolaria nuttallii and Tagelus californianus both had shell sizes which were signifi cantly less than when they occurred in a sympatric community. Both length and height of 11acoma nasuta in Edison Canal {allopatric) and

Mugu Lagoon were significantly less than sympatric organisms collected at Morro Bay. Macoma secta from Lower Newport Bay (allo patric) was significantly smaller than~ secta from Morro Bay {sympatric). s. nuttallii from Mugu Lagoon were significantly smaller when compared with the sympatric population at Lower Newport Bay. --T. californianus in its allopatric population at Back-Bay Newport was significantly smaller than individuals in the sympatric community from Edison Canal. Some populations showed no significant diff"erence in size between allopatric and sympatric populations.

~ secta (allopatric) was the same size as M. secta collected sympatrically in the same area. Florimetis obesa from Morro Bay Table 4. Mean length, height, and t-values for allopatric and sympatric species. mean mean Macoma nasuta length t- height t- em s.d. values em s.d. values Mugu Lagoon a 3.42 1.02 2.48 0.84 vs. 1.2277 1.0577** Edison Canal s 3.64 0.44 2.65 0.30

Mugu Lagoon a 3.42 1.02 2.48 0.84 vs. 3.4475* 4.3575* Morro Bay s 4.26 1.03 3.35 0.91 Edison Canal a 3.69 o.-86 2.80 0.70 vs. 1. 773 1.0973 Edison Canal s 3.64 0.44 2.65 0.30 Edison Canal a 3.69 0.86 2.80 0.70 vs. 11.475* 2.8975* Morro Bay s 4.26 1.03 3·35 0.73 Nacoma secta

Lower Newport Bay a 4.73 0.96 3.65 0.27 vs. 2.1337 3.3637* Lower Newport Bay s 5.30 0.69 4.17 0.63 Lower Newport Bay a 4.73 0.96 3.65 0.27 vs. 0.6840 o·.13 Morro Bay s 4.67 0.97 3.63 0.73 40

~lus californianus Back-Bay Newport a 7.26 1.54 2.)0 0.33 vs. 3.16119* 9.21119* Edison Canal s 5.65 2.17 1.83 0.17

Sangu!nolar~a nuttallii Mugu Lagoon a 4.12 0.82 2.94 0.75 8 * * Lowe~ Newport Bay s 4.84 0.67 3.2995 3.36 o.6s 2.4795 Florimetis obesa

Morro Bay a 3.98 1.08 2.92 0.87 vs. 3.2995* 2.4795* Morro Bay s 3.71 1.35 2.74 0.83 ** subscripis indicate the degrees or freedom a allopatric population * significant difference at 0.05 level s sympatric community 31

(allopatric) was not significantly different in size than its sympatric population also at Morro Bay.

Regression analyses (Table 5 and Appendices 1-5) using both shell length and shell height, showed that there was no difference in the slope of the regression line between allopatric and sympatric species for Sangui.nolaria nuttallii, Tagelus californianus, Macoma secta and ~orimetis obesa. However, Macoma nasuta from a sympa~£ic community in Morro Bay was significantly different than the allopatric population at Edison Canal.

Substrate Analyses

Sediment distribution for each of the collection areas is shown in Table 6 and indicates differences exist among areas. Mugu

Lagoon (Sanguinolaria nuttallii area), Edison·canal, Back-Bay Newport and Morro Bay all have a unimodal distribution with the mode being fine sand (125-250 ~), and the majority of the sediment being fine and medium sand ( 125-500 }-\). Mugu Lagoon where ~ nuttallii was collected had 77.5~~. Morro Bay was unique in that 75% of the sediment was fine sand. Lower Newport Bay was the only site which had the majority (65.35~6) of the sediment in medium and coarse size classes. The organic carbon content of the substratum was much the same for all but two areas. At Mugu Lagoon, Lower Newport Bay, and Herro Bay the organic carbon content was between 1.75% and 2.0%. However, Back-Bay Newport and Edison Canal had a much higher organic carbon content, 5.~~ and 6.~~ respectively. 32

~able 5. Slopes of regression lines and t-values comparing the slopes of those lines.

Macoma nasuta slope t-value Mugu Lagoon a 1.07 vs. Edison Canal s 1.23

Mugu Lagoon a 1.07 vs. Morro Bay s 1.00

Edison Canal a 1.23 vs. Edison Canal s 1.25

Edison Canal a 1.23 vs. Morro Bay s 1.00 Macoma -secta Lower Newport Bay a vs. I>1orro Bay s

Lower Newport Bay a vs. Lower Newport Bay s

Jagel~s californianus

Back-Bay Newport a vs. Edison Canal s

~anguinolaria nuttallii

Mugu Lagoon a 1.20 vs. Lower Newport Bay s 1.12

Florimetis obesa

Morro Bay a 1.10 vs. Morro Bay s 1.10 ** subscripts indicate the degrees of freedom a allopatric population * significant difference at the 0.05 level s sympatric community 33

Table 6. Sediment size distribution and organic carbon content from the areas of study, percent by weight.

Lower Mugu* Mugu** Edison :Back-Bay Newport Morro size Lagoon Lagoon Canal Newport :Bay :Bay 1000-2000 It .29 2.73 .52 6.68 5·97 very coarse sand 500-1000 A 6.23 9.66 2.5 10.19 18.77 0.45 coarse sand

250-500 p. 14.09 28.53 31.13 20.26 46.58 2.45 medium sand

125-250 JJ. 22.99 48.49 52.08 42.43 15.96 75.12 fine sand ' 62-125 'A 25.96 10.11 10.33 12.01 6.99 21.14 very fine sand 62 p. 30.41 0.45 3.32 8.0 5.97 0.8 silt or clay organic carbon 1.87 2.0 6.8 5.9 1.7 1.7

* ~coma nasuta population ** Sanguinolaria nuttallii DISCUSSION

Feedi~ Behavior

Both the- stomach contents and siphonal behavior indicates the manner by which the organism obtains its food. The food of suspen sion feeders can be plankton, dissolved organic matter, organic aggregates, and bacteria (Levinton, 1972). The food available for deposit feeders consists of plankton (live or dead) deposited on the bottom, dissolved organic matter, plant detritus that has been broken down into small particles, diatoms and bacteria (Levinton, 1972). The organisms in this study are classified into three groups based on the type of material found-in their guts and the observed activity of their inhalent siphon. Macoma secta ~ms a typical deposit feeder as described by Yonge (1949) and Reid and Reid (1969). The second group contains organisms which are suspension feeders. This type of behavior has been described in the Tellinacea by Wade (1965), Pohle (1966, 1967, 1969, 1972), and Reid and Reid (1969). Sanguinolaria nuttallii and Tagelus californianus function as suspension feeders (Table 1).

The third category is one in which the organism practices both deposit and suspension feeding. This behavior has been described in the Telli.nacea by Reid and Reid (1969), and Pohle (1973). Flori metis obesa and Macoma nasuta can be categorized in this third group.

Macoma nasuta is usually described as a deposit feeder (Yonge,

1949)~ but Reid and Reid (1969) described it as a suspension feeder. However, I found that this animal exhibited both suspension and

34 deposit feeding behavior. When M. nasuta was allopatric in Mugu

Lagoon and Edison Canal it .was a deposit feeder with large amounts of silt and debris present in the stomach and the siphon was active, inhaling the substrate. However, M. nasuta from Morro Bay (sympatric) had smaller amounts of silt and debris in the stomach (deposit feeder) but the inhalant siphon was observed out and active, not inhaling substrate (suspension feeder). Although I observed~ nasuta from

Morro Bay suspension feeding, at some unobserved time, it was deposit feeding. It was thus able to partition its food sources in a temporal manner.

Florimetis obesa found both allopatrically and sympatrically in Morro Bay had deposit feeding stemach and mantle cavity contents, but the siphonal behavior was that of a suspension feeder. So ~ obesa at times was suspension feeding and at other times ingesting material deposited on ~he substratum. This same type feeding behavior took place in all areas that F. obesa was collected.

Although Florimetis obesa always showed combined suspension and deposit feeding behaviors, Macoma nasuta was the only tellinacean which shifted its feeding behavior from deposit (allopatric) to sus pension-deposit (sympatric). This change may have been in response to competition for food with Macoma secta which is a deposit feeding tellinacean. It would be interesting to examine more closely the distribution of M. nasuta along the Pacific coast in comparison to other Tellinacea. The ability to shift feeding behavior would increase the organisms adaptability, thus allowing it to occupy a greater number of areas. 36

In all collecting areas there were other suspension and deposit

feeding organisms. Those I observed were: in Morro Bay, ghost shrimp

(Callianassa californiensis), and the gaper clam (Schizothaerus

nuttallii); in Mugu Lagoon, bivalves (Protothaca staminea and Mytilus

edulis), and Callianassa californiensis; in Edison Canal, the cockle

(Chione rosaceus), worms (§!E?Pculus nudus, Urechis caupo and Glycera -americanus); in Lower Newport Bay, bivalves (Saxidomus---- nuttallii and ~ arenaria), and a crab (Heterocrypta ?Ccidentalis); and ir Eack- Bay Newport none were observed. These and other deposit and suspen

sion feeding organisms would affect the use of a given area's food

resource. This might affect the species and density of tellinaceans

present. Further studies would be necessary to clarify community

food resource utilization.

In Pianka's discussion about competition of closely related

species, he notes that they are often quite similar in many ways--

morphologically, behaviorally, and ecologically. This is seen to be

the case in the Tellinacea in terms of their feeding behavior.

Because pairs of these species'inhabit the same area, there should,

according to Pianka (1978) and Gause (1934), be some ecological differences between the species resulting from their ability to

utilize the available resources. Pianka (1978) cites three possible

differences that might occur: "the species exploit different habi tat·s

or microhabitats (differentiated patterns of temporal activity)."

My research indicates that members of the Tellinacea exist sympatri-

cally because they exhibit a difference in feeding behavior, both

temporally and in the type of food they eat. 37

Popu1ation Densiti

The density of an allopatric population was compared with the

density of that same species occurring sympatrically and also with

the mean density of all sympatric tellinaceans. This was done in

order to determine if an area's food resources had some effect on

the number of tellinaceans using that resource.

If there is competition for the same food resource, and that

food resource is limited, it would be expected that there will be

a decrease in the number of coexisting individuals of a given species.

However, no decrease in numbers would indicate there is no direct

competition for the same food resource, but a partitioning of the resource. My results show that within a given geographical location where both allopatric and sympatric populations exist there is no

difference in the number of individuals of a species between the allopatric population and sympatric community. Florimetis obesa from 2 Morro Bay (allopatric) had a mean &ensity of 5.0/0.5 m while the 2 mean density for F. obesa (sympatric) was 4-75/0.5 m • Macoma secta 2 from Lower Newport Bay (allopatric) had a mean density of 5.50/0.5 m 2 and the mean density forM. secta (sympatric) was 5.0/0.5 m • A density increase of all coexisting tellinaceans when compared with

the density of an allopatric population would also imply a parti-

tioning of resources and no direct competition for those resources. 2 The density of~ obesa from Morro Bay (allopatric) was 5.0/0.5 m 2 while tl1e coexisting tellinacean density in Morro Bay was 16.0/0.5 m •

Also ~ secta occurring allopatrically in Lower Newport Bay had a 2 population density of 5.50/0.5 m while the coexisting tellinaceans' 38 '

2 density was 10.75/0.5 m • Significant differences exist between population densities from different geographical locations. An organism's location in the environment and its density are dictated by both biotic and abiotic factors. Studies of total food availability, environmental pollu- tion, r~edators, biotic stress, and shell structure would help explain these differences.

Substrate Analys~

The organisms observed prefer to live in sediment which is mostly fine sand (125-250 ~). Sediments appear to have no effect on feeding behavior. In Morro Bay which had 97.07% silt to fine sand both suspension and deposit feeders (Macoma nasuta, Florimetis obesa) were collected. In Lower Newport Bay which had 87.2~/o fine sand to very coarse sand both suspension and deposit (Macoma secta,

Sanguinolaria nuttallii) feeders were collected. This would indicate that there was no preference for a particular sediment type by either deposit or suspension feeders.

The organic content was much the same for all areas except

Edison Canal (6.~/o) and Back-Bay Newport (5.9%). ~a~elus california-

~was present in both locations. The very high population density of ~ palifornianus at Back-Bay Newport may be related to the high amount of organic carbon. Although T. californianus is a suspension feeder, water currents could stir the organic carbon and make it available to these organisms.

Shell Size

The slopes of the regression lines (appendices 7-11) were the 39

same for allopatric and sympatric populations of the same species

from all areas. This would indicate that differences in biotic and

abiotic conditions such as sediment type, occurrence with other

organisms, and predators have no effect on the growth of these

tellinaceans. The individuals even in different environments are

able to obtain all the resources necessary to maintain a similar

growth pattern.

When comparing length or height for allopatric and sympatric

Sanguinolaria nuttallii and Tagelus californianus the allopatric

population had a smaller shell size than the sympatric population.

The regression analyses showed that both populations had the same relationship between shell length and shell height. The difference in length or height is a size class difference. The ~ nuttallii

population at I>lugu Lagoon (allopatric), for example, may have been affected by the sediment washed into the lagoon the previous spring when there were heavier than normal rains causing large amounts of

sediment to be deposited in the lagoon. The increase in sediment or fresh water resulted in a die-off of burrowing organisms. This would have affected the population density and shell size.

Let~th and height comparisons and_regression analyses show

that Macoma nasuta from Morro Bay, where it was a suspension

feeder, is different th~n populations from Edison Canal, where it is a deposit feeder. The difference in shell size may be, in part

due to the change in feeding behavior or the environment in Morro

Bay. 40

LITERATURE CI~~D

Abbott, R. Ta 1954. American Seashells. D. Van Nostrand Co., Inc., Princeton, N.J.

Bradfield, A:w. and Newell, G.E. 1961. The Behavior of Macoma bal thi-· ~ (L) J. Mar. Biol. Assoc. U.K. !1:81-87.

Carver, Robert. E. 1971. Procedures in Sedimentaxy Petrology. Wiley Interscience, New York. 653PP• Gause, G.F .. 1934. The struggle for existence. Williams and Wilkins Co., Baltimore, 163pp. Holme, N.A. 1961. Notes on the mode of life of the Tellinidae (Lamellibranchia). J.Nar. Biol. Assoc. U.,K. 41:639-703.

Hutchinson, G.E. 1957. Concluding remarks Cold Springs Harbor Symp. Quant. Biol. 22:415-427. Levinton, J. 1972. Stability and tropic structure in deposit feeding ru1d suspension feeding communities. Am. Nat. 106:472-481.

Maurer, D. 1967. Mode of feeding and diet, and synthesis of studies on marine pelecypods from Tomales Bay, Cal. Veliger. 10:27-76.

Mclean, J .H. Marine Shells of Southern California. Los Angeles County Museum of Natural History. Science Series. ~ Zoology no~ 11.

Pianlr..a, E.,R. 1978. Evolutionary Ecology. Harper and Row, New York, 397PP•

Pohlo, R.n. 1966. A note on the feeding behavior of ~elus ~alifornianus (Bivalvia:Tellinacea) Veliger, ~:225.

Pohlo, R.H. 1967. Aspects of the biology of Donax gouldi~ and a note on the evolution in Tellinacea(Bivalvia). Veliger ,2:330-337. Pohlo, RaH. 1969. Confusion concerning deposit feeding in the Tellinacea. Proc~ Malacol. Soc. London, 2Q:361-364.

Pohlo, R.H. 1972. Feeding and associated morphology in £ap~nolaria nuttallii (Bivalvia:Tellinacea). Veliger j.4:298-301. Pohlo, R.H. 1973. Feeding and associated functional morphology in Tagelus californianus and Florimetis obesa. (Bivalvia: Tellinacea J Malacologi.a 12: 1-11 • · --- LITERATURE CITED cont. Purchon, R.D. 1963. A note on the biology of Egeria radiata Lam8 {Bivalvia:Donacide) Proc. Malacol. Soc. London. 22:251~271.

Reid, R.G. and Reid, A. 1969. Feeding processes of members of the genus Macoma. J. Zool. ill:156-184. Simpson, G.G., Roe, A., Lewontin, R.C. 1960. Quantitive Zoology. Harcourt, Brace and Co. New York~ 440pp.

Sokal, R. and Rohlf, F.J. 1969. Biometry. W.H. Freedman Co., San Francisco, 776pp. Wade, B.A. 1965. Notes on the ecology of Donax detriculatus (Linne) Proc. Gulf Caribb. Fish. Inst. 17th annual Session. 36-41.

Yonge, C.M. 1949. On the structure and ada~tations of the Tellinacea deposit-feeding Eulamellibranchia. Phil. Trans. Roy. Soc. B., 234:29-76. 42

Appendix 1~ Dimensions (in em) for Macoma nasuta collected from Mugu Lagoon (allopatric).

Sample 1 Sample 2 Sample 3 Sample 4 Length Height Length Height Length Height Length Hei@:t 5.0 3.7 s.o 4.3 s.o 3. 7 5.0 3. 7 5.0 3.7 3.7 3.2 5.0 3.8 5.0 3.8 3.7 3.2 3.2 1.9 4.5 3.8 4.6 3.8 5.0 3.7 1.9 1.2 3.7 2.5 3.7 2.5 5.0 3.7 5.0 3.6 3.2 2.6 3.1 2.6 3.7 2.5 3.7 2.5 3.2 2.5 3.1 2.5 3.2 1.9 3.2 1.9 3.2 2.5 3.2 2.4 3.2 1.9 1.2 1.2 3.2 2.5 2.6 1.2 3.2 1.9 3.2 2. 5 3.2 2.5 2.5 1.9 3.2 2.4 3.2 2.4 2.5 1. 9 2.6 1.2 3.2 2.4 2.5 1.9 2.6 1.2 1.9 1.3 2.6· 1.2 1.9 1.2 1.2 1.2 3.2 1.2 3.2 1. 9

Appendix 2. Dimensions for San inolaria nuttallii collected from Mugu Lagoon (allopatric in em.

Sample 1 Sample 2 Sample 3 Sample 4 Length Height Length Height Length Height Length Height 5.7 3.8 4.5 3.2 5.0 3.8 s.o 3.8 5.7 3.8 5.0 3.8 4.5 3.8 5.0 3.7 5.6 3.7 3.8 3.2 3.9 3.1 4.9 3.2 4.4 3.1 3.8 3.2 3.8 3.2 5.0 3.8 4.4 3.1 3.8 2.8 3.2 2.5 3.8 2.4 4·4 3.2 3-7 2.5 4.5 3.1 3.7 2.2 4.4 3.1 3.2 2.6 3.2 2.2 4.3 2.8 3.8 3.1 3.8 3.2 2.5 1. 9 1.9 1.2 3.8 2.5 3.7 2.9 3.2 2.3 4.5 3.1 3.7 2.5 3.7 3.2 3.2 2.3 4.4 3.0 3.8 2.5 3.2 1.9 2.4 1. 9 3.8 3.1 3.8 2.4 3.2 1. 9 3.1 1.3 3.7 3.2 3.7 2.4 3.2 2.5 3.0 2.5 3.8 3.1 3.1 2.4 2.5 1.8 3.1 2.4 3.6 3.0 3.2 2.4 3.5 2.4 3.0 2.4 3 .. 1 2.5 3.2 2.5 3.1 2.4 2.9 2.5 3.0 2.4 3.2 2.4 3.1 2.6 3.1 2.3 3.1 2.4 3.0 2.4 2.9 2.5 2.9 2.5 43

Appendix 3. Dimensions (in em) for Macoma nasuta collected from Edison Canal (allopatric).

Sample 1 Sample 2 Sample 3 Sample 4 Length Hei@t Length Height Len~th HeiB:ht Length HeiB:ht 4.5 3.2 5.7 4.5 5.7 3.8 5.0 3.8 5.0 3.8 5.8 4.5 5.0 3.2 5.0 3.8 3.8 3.2 5.8 4·5 5.0 3.2 5.0 3.7 4-4 3.2 5.0 3.8 5.0 3.2 5.0 3.8 4.4 3.8 5.0 3-7 4.5 2.8 4.5 3.2 3.8 2.5 5.0 3.8 4·5 2.8 4.5 3.7 3.2 2.5 4.6 3.2 4.4 2.7 4.8 3.5 3.2 2.5 4.4 3.2 4-5 2.8 2.5 1.9 3.2 1.9 4-5 3.1 3.8 2.6 3.2 2.5 3.8 3.1 3.8 2.6 2 .. 5 1.9 3.7 2.5 3~7 2.6 ,.8 2.5 3.7 2.2 3.8 2.4 3.8 2.4

Dimensions (in em) for Macoma nasuta collected from Edison Canal (sympatric).

Sample i Sample 2 Sample 3 Sample 4 Len~h Height Len8:th Height LenB:th Height Len~th Height 4.4- 3.0 3·9 2.7 4.5 3-3 3.9 2.7 4.2 2 .. 9 3.6 2.6 4.7 3-3 3-3 2.9 4.0 2 .. 9 3.6 2.5 3.6 2.5 3.2 2.9 3·3 2.3 4.0 2.9 3-4 2.5 3-5 2.5 3.3 2.5 3.3 2.9 4.0 3.0 3.4 2.4 3.2 2.3 3.2 2.2 2.8 2.0 3.4 2.6 3.9 2.7 3-3 2.3 3.9 2.8 2.5 2.5 3.6 2.5 3·4 2.5 Dimensions (in em) for ~_gel)s californianus collected from Edison Canal (sympatric •

Sample 1 Sample 2 Sample 3 Sample 4 Length Hei.s:,ht Length Height Length Height Length Height 5·5 1.8 7·5 2.5 9.1 2.7 7.3 2.5 8.4 2.6 7-3 2.6 7.4 2.5 7-7 2.3 8.7 2.6 6.3 2.0 7·5 2.2 7.3 2.3 7.2 2.2 7.6 2.6 6.6 2.4 4.8 1.4 s.o 2.2 7.2 2.3 7.4 2.4 6.4 2.1 ;:__::_: ___ :-~_:_~-::_:_::_____:_: ____ c__:_-_::__ _::__.::.:__~-=------

Appendix 4. Dimensions (in em) for Tagelus californianus collected from Back-Bay Newport (allopatric).

Sample 1 Sample 2 Sample 3 Sample 4 _!!ens:th Hei~ht Length H~ight Len8:th Height Length Heig_ht ?.0 1.9 5.3 1.8 5.3 1.8 s.o 1.7 5.3 1.8 6.3 2.1 5.6 2.1 5-3 1.7 5.3 1. 7 6.5 2.0 4.9 1.8 6.1 2.1 5.0 1.8 5.0 1.9 4-9 1.7 5.1 1.7 5.1 1.8 5.2 2.0 5.0 1.7 4.8 1.8 5.3 1.. 8 4.9 1.9 4.8 1.7 5.3 1. 7 5.,3 1.8 5.1 1.8 5.9 2.1 5.3 1.6 5.3 1.8 6.0 2.0 6.2 2.0 5.3 1.7 4.7 1.7 5.1 1.9 5.0 2.0 5.2 1.7 5.6 1.9 5.4 1.9 4.9 1.7 5.0 1.6 5.6 1.8 5.5 1.9 5.1 1.7 4.9 1.6 5.4 1.8 5.6 2.0 5.8 2.0 4.7 1.6 6~ 1 2.1 X 2.0 5.0 1.7 4.7 1.6 5.1 2.9 X 1.8 4.8 1.8 5.0 1.8 5·7 2.9 5.7 2.1 4.9 1.8 5.0 1.8 6.0 2.1 X 1.8 5.1 1.7 5.2 1.7 5.7 1.9 3.7 2.1 5.7 2.0 5.4 1.6 4.8 1.8 ·4.8 1.6 4-9 1.8 6.7 1.8 4.8 1.7 4.6 1.6 4.5 1.6 5.1 1.8 4.7 1.8 4.7 1.7 5.2 1.9 5.3 2.0 5.2 1.7 5.8 2.1 4-7 1.7 5.2 2.0 5.3 1.8 5.2 1. 8 5.0 1.9 5.2 1.9 5.1 1.9 5.. 3 1.9 4.8 1.6 4.8 1.8 4.7 1.7 4.9 1.7 4.5 1.7 4.8 1.7 4.4 1·1 4-9 1.7 4.9 1.7 4.4 1.5 5.0 1.7 4.9 1.8 5.3 1.8 5.0 1.7 5.0 1.7 ------

45 '

Appendix 5. Dimensions (in em) for Macoma secta from Lower Newport Bay (allopatric).

Sample 1 Sample 2 Sample 3 Sample 4 LeP..gth Hei_s:h t Length Height Lepgth Height Length Height 6".3 5.8 b.3 5.8 ).8 3-7 5.8 3.7 5.2 4.1 5-5 4.1 5.2 4.0 4.0 3.0 5.0 3.8 4.0 3.0 4.8 3-7 3 .. 8 3.0 4-5 3-4 4.3 3.2 4.1 3.2 3.2 2.8 2.8 2.2

Dimensions (in cin) for Sangu.inolaria nuttallii ~ollected from Lower Newport Bay {sympatric).

Sample 1 Sample 2 Sample 3 Sample 4 Length Height Len~th Height Length Height Length Heigh~ s:-r--3.9 5-7 4.5 4.5 3.4 5.7 3.8 5.8 4.2 5.8 4.5 5.7 3.8 1·9 5.9 4.8 3.7 5.6 3.1 4·9 3.8 4.1 3.2 4.4 3.0 5-3 3-7 3.8 2.5 6.7 5-3 3.7 2.4 5.1 3. 5 3.2 2.5 2.3 1. 7 Dimensions (in em) for Macoma secta collected from Lower Newport Bay (sympatric). Sample 1 Sample 2 Sample 3 Sample 4 Length Height Length Hei~ht Length Height Length Height 5·3 4.2 4 .. 5 3.4 5.3 4.2 5.8 4.5 6.0 4.6 5.8 4.5 5.1 4.0 4.8 3.7 5·5 4.1 4.8 3.7 5.0 3.9 4.1 3.2 5.8 4.5 4.1 3.2 4.5 3.5 4·5 3-4 3.8 3.0 2.8 2.1 3.2 2.8 2.8 2.2 ------

46 p '

Appendix 6. Dimensions (in em) for Florimetis Obesa collected from Morro Bay (allopatric).

Sample 1 Sample 2 Sample 3 Sample 4 !!ength Height Length Height Length Hei~ht Length Heigl:lt 3·3 2.4 3-7 2.7 5.8 4.2 3.7 2.7 3.3 2.3 2.7 1.8 3.2 2.3 2.7 1.8 4.2 3.1 1.8 1.4 3.4 2.3 5.0 3.5 5.1 4.0 3.3 2.5 3.8 2.8 5.2 4.1 5.6 4.6 4.0 3.0 4.8 3.5 5.1 3.6 Dimensions (in em) .for Macoma nasuta collected from l

Sample 1 Sample 2 Sample 3 Sample 4 Len~th Hei~ht Length Height Length Hei,B:ht Length Height 4.8 4.3 4.0 3.2 5.0 3·7 4.4 3.0 4.7 4.2 4.5 3.6 3.7 3.0 5.0 3.8 5·4 3.6 4.6 3·9 5.0 3.7 4.0 2.. 8 5.5 4.8 5.4 4.0 3.7 2.5 3.2 2.5 5.2 4.1 5.7 4.0 2.5 1.9 3·3 2.5 5.1 4.2 5.3 4.6 1. 9 1.2 3.2 2.5 4·9 3·7 5.3 2.9 2.8 2.0 3·3 2.9 3.3 2.9 Dimensions (in em) for Florimetis obesa collected from Morro Bay ( sympa tri c) •

Sample 1 Sample 2 Sample 3 Sample 4 Length Height Length Height Length Height Len~th Height 5.6 4.5 6.1 4.5 3·3 2.4 5.1 3.6 2.7 1.8 5.1 3.6 3.2 2.4 3.7 2.7 1.8 1.4 3.7 2.7 2.7 1.7 3.3 2.6 2.2 1.5 5.1 4.0 1.8 1.4 3.2 2.5 3.3 2.5 5.8 4.5 2.8 1.7 Dimensions (in em) for Macoma secta collected from Morro Bay (sympatric). Sample 1 Sample 2 Sample 3 Sample 4 Len~~h Height Le!'l8:th Height Length Height Length Height 4.8 4.2 5.3 4.2 6.3 5.5 5.3 4.2 5·3 4.2 5·4 4.3 5.8 3.8 5.4 4.2 5-5 4.1 5.5 4.1 4.0 3.2 5.8 4.6 5.8 4·5 5.8 4.6 3.8 3.0 6.0 5.0 4·3 3.2 47

Appendix 7. Regression analyses for Tagelus californianus. 00 0 o':oo~o 60 10 0 I 7 I I e I

6 •

5 • 0

--- e :Back-:Bay Newport (allopatric)

.1 ----- o Edison Canal ( sympa tric)

1 2 3 4 5 height em

.r,. 48

Appendix 8. Regression analyses for Sanguinol~i~ nuttallii.

, 6 , , ·{ .o 0 'o o- 0 , • ~

5 •

0 4 •• ~ ~ , ~ Q) .,, r-1 , 3 , , • ' 0 2 •

---o Mugu Lagoon {allopatric) ' -- --- O Lower Newport Bay { sympa tric) 1

1 2 3 4 5 height em 49

Appendix 9. Regression analyses for Macoma nasuta.

6 -

• Mugu Lagoon (allopatric) --- -· o Edison Canal (allopatric) 1 -·-·-A Morro Bay (sympatric) -··-··• Edison Canal (sympatric)

1 2 4 5

height em Appendix 10. Regression analyses for Florimetis obesa.

6 0

0 ~

1 2 3 4 5 height em ------~------

Appendix 11. Regression analyses for Macoma secta.

• 1/

4 ~ ti ~ 1""1

3 ooe

---• Lower Newport Bay (allopatric) -----o Lower Newport :Bay (sympatric) 1 -·-·A Morro :Bay (sympatric)

1 2 3 4 5 height em