vertical distribution ofmollusks on the rocky …...vertical distribution ofmollusks on the rocky...

Pacific Science (1989), vol. 43, no. 4© 1989 by University of Hawaii Press. All rights reserved

Vertical Distribution of Mollusks on the Rocky Intertidal of Easter Island 1

CECILIA OSORIO AND VICTOR CANTUARIAS2

ABSTRACT: Horizontal and vertical distribution ofmollusks was studied in therocky intertidal of Easter Island (27°09' S,109°26' W) in January and again inSeptember 1986. Organisms are zoned from the upper to the lower intertidal. Inthe upper horizon dominant species are Nodilittorina pyramidalis pascua, Rehderella belyaevi, Nerita sp., and Planaxis akuana, together with crustaceans, decapods and echinoderms. In the middle horizon dominant species are Plaxiphoramercatoris, Dendropoma sp., Antisabia sp., and Pilosabia sp. Mid-horizon poolssupport algae; the only relatively abundant coral, Porites lobata; numerousgastropods such as Stomatella and Euplica; crustaceans; and echinoderms. In thelowest horizon Cypraea caputdraconis and Echinometra insularis are dominant.The latter species is a rock borer that builds "pots" forming microhabitats sharedwith other organisms. Some specimens of Dendropoma, Pocillopora, andEchinostrephus were also found in this horizon. No great differences in distribution of organisms among the south, northeast, and northwest sectors of theisland were distinguished in an index of similarity. Distribution patterns atEaster Island are comparable with those in other tropical areas where the samefamilies and genera are found. At Easter Island the species are different becauseof the high degree of endemism among the mollusks.

temperatures fluctuate between 24°C in summer and 20°C in winter. The extreme temperatures (maximum and minimum recordedtemperatures) were 30.6°C (25 December 1964)and 15.6°C (9 August 1979), according to records kept from 1957 to 1978 by the InstitutoHidrografico de la Armada de Chile (ChileanNavy Hydrographic Institute). Because of itsclose relationship with the Pacific anticyclone(Hauser 1986), the island has rains throughoutthe year.

The human population of Easter Island isnow about 2300. In prehistoric times the island was overpopulated, reaching on averagefrom 10,000 to 15,000 inhabitants. The shoreline perimeter of 57 km (Boonen 1897) is continuously searched by the islanders for foodand raw materials for handicrafts.

Most of the scientific literature concerning Easter Island deals with taxonomic andbiogeographic problems of different animalgroups, e.g., Fuentes (1914), Wells (1972), andCea and Di Salvo (1982)-corals; Garth(I 973)-crabs; Kohn and Lloyd (1973)polychaetes; Kohn (l978a), Pinochet (1980),

302

EASTER ISLAND, or Rapa Nui (lat. 27°09' S,long. 109°26' W), a Chilean possession in thesoutheast Pacific, is one of the most isolatedislands in the Pacific Ocean. Its marine faunais primarily derived from the Indo-West Pacific(Rehder 1980, Ladd 1960, Ekman 1953), butbecause of its extreme isolation and otherconditions typical of the area there is markedendemism among the mollusks. Kohn andLloyd (1973) found that 67-88% of the corals,crustaceans, gastropods, and fish at Easter Island are also present elsewhere in the IndoPacific, and most of the remainder are endemic. Rehder (1980) considers about 42% ofthe mollusks endemic. Schilder (fide Rehder1980) recognized Easter Island as an independent zoogeographical province and designatedit the "Rapanuian" or Easter Island Province.

Easter Island has a temperate to subtropical climate. Monthly average ocean surface

1 Manuscript accepted 12 December 1988.2 Departamento de Ciencias Ecol6gicas, Facu1tad de

Ciencias, Universidad de Chile, Casilla 653, Santiago,Chile.








302












302





Intertidal Distribution of Mollusks-OSORIO AND CANTUARIAS 303

and Rehder (1980)-mollusks; Fell (1974) andCodoceo (1974)-echinoderms; Randall andMcCosker (1975), and Randall (1976)-fishes.Castilla and Rozbaczylo (1987) published abibliographic review of the littoral marineinvertebrates. Santelices and Abbott (1988)discussed algal zonation and biogeography.

Relatively little work has been done onecology and the distribution of organisms onEaster Island. The aim of this work is to characterize the vertical and horizontal distribution of mollusks in the rocky intertidal, tocompare species composition of intertidalmollusks on different sectors of the coastline,and to compare the distribution and composition of the Easter Island intertidal fauna withthat in temperate and tropical areas.

MATERIALS AND METHODS

Collections were made on Easter Islandfrom 9 to 16 January and from 11 to 18 September 1986. Average tidal heights duringthe study periods were 0.82 m and 0.27 m inJanuary and 0.59 and 0.13 m in September.Seven sections of the rocky intertidal wereselected for transects (Figure 1): Hanga Roa,

FIGURE 1. Easter Island, showing study areas.

Akahanga, Hanga Nui, Vinapu, and Anakena,which are areas of basalt shoreline; and Vaihuand Ovahe, which are beaches.

Mollusks were obtained in transects perpendicular to the coastline at Hanga Roa andVaihu during low tides. Collections were madeon exposed and protected rocks, in crevices,and under rocks and algae. Three biotic zoneswere established parallel to the shoreline, eachdelimited by numerically and macroscopicallydominant species used as biological indicators.

Sorensen's (1948) index of similarity wasused to compare mollusk populations in thedifferent sectors studied. Species collectedamong rocks and shells found in the work areawere included in the calculations.

RESULTS

Distribution

Sixty-four mollusk species were identified(Table 1). Fourteen (22%) of the species werecommon to five to seven of the seven sectorssampled; 23 (36%) were found in a single area.Thus, 14 species were restricted to Anakena,four to Hanga Roa, three to Hanga Nui, and

La Perouse

'"

Hanga NUl

•

-+- 27°tO'5

Og" 2<5wo










RESULTS

Distribution


La Perouse

'"

Hanga NUl

•

-+- 27°tO'5

Og" 2<5wo










RESULTS

Distribution


La Perouse

'"

Hanga NUl

•

-+- 27°tO'5

Og" 2<5wo

304 PACIFIC SCIENCE, Volume 43, October 1989

TABLE I

MOLLUSK SPECIES RECORDED IN THE ROCKY INTERTIDAL OF EASTER ISLAND"

SPECIES VI AN HN OV HR VA AH

Plaxiphoramercatoris Lelaup* x x x x

Emarginulavelascoi Rehder x x

Diadoragranifera Pease x x x x x

Euchelusalarconi Rehder* x x x x x

Stomatellaesperanzae Rehder* x x x

Neritalirellata Rehder* x x x x xmorio (Sowerby) x x x x x x x

Nodilittorinapyramidalis pascua Rosewater x x x x x x x

Rissoinaturricula englerti Rehder x x x x x

Merelinacrassula Rehder x x x

Zebinatridentata crassilabrum (Garrett)* x x x

Assimineavulgaris (Webster) x x x

Heliacuscodoceoae Rehder* x

Dendropomasp. x x x x x

Caecumsp. x

Cerithidiumactinium Rehder x

Triphorasp. x

Planaxisakuana Rehder* x x x x x x xfasciatus Pease x x

Melanellacumingi (A. Adams) x x

Balcisaciculata (Pease) x x

Vitreolinawareni Rehder* x

Epitoniumpyramis Tinker x

Hemiliostracabahamondei Rehder* x

Antisabiafoliacea (Quay and Gaimard) x x x x ximbricata (Gould) x x x x x

Pilosabiatrigona (Gmelin) x x x

Fossaruscumingii A. Adams x x x

Strombusmaculatus Sawerby x x

Trivirostrapellucidula (Reeve) x


TABLE I
















Caecumsp. x


Triphorasp. x













TABLE I
















Caecumsp. x


Triphorasp. x












Intertidal Distribution of Mollusks-OSORio AND CANTUARIAS 305

TABLE I (continued)


Cypraeacaputdraconis Melvi11* x x x x xeng/erti Summers and Burgess* x

Moru/apraecipua Rehder* x

Neothaisnesiotes Iredale x x x x x x x

Pascu/acitrica (DaB)* x x

Zafronapusi//a Pease* x x

Eup/ica/oisae Rehder x x x x

Seminellaornata (Pease)* x x

Nodochi/apascua (Hertlein)* x x x x

Caduciferdecapitata eng/erti Hertlein* x x x x x

Mitraflavocingu/ata Lamy* x x

Granu/apascuana Rehder* x

Lienardiaexi/irata Rehder* x x x

Conusmi/iaris pascuensis Rehder* x x x x x x

Acuminiavenosa (Hinds) x

Egente/ariasty/ata (Hinds) x

Retusapusi//a (pease) x

Smaragdinellaca/ycu/ata (Broderip and Sowerby) x

Siphonariapascua Rehder* x x x x x

Wi//iamiaradiata Rehder x

Me/ampuspascus Odhner* x x x x x x

Trimuscu/usodhneri (Hubendick) x

Rangitotoasp.* x

Ap/ysiasp. x x x

Nudibranchiasp. x

Modio/usmatris Pilsbry x

Septiferbryanae (Pilsbry) x

Barbatianuttingi (DaB) x x

Codakiabella (Conrad) x x x x

Ch/amyspasca DaB* x


TABLE I (continued)























Rangitotoasp.* x

Ap/ysiasp. x x x

Nudibranchiasp. x





Ch/amyspasca DaB* x


TABLE I (continued)























Rangitotoasp.* x

Ap/ysiasp. x x x

Nudibranchiasp. x





Ch/amyspasca DaB* x


TABLE I (continued)

SPECIES VI AN HN OV HR VA

Lasaeahawaiensis Dall x x x

Semeleaustralis (Sowerby) x x

TellinamauiaDall x

Mactridaesp. x

AH

x

"Abbreviations of sectors selected for transects: VI, Vinapu; AN, Anakena; HN, Hanga Nui; OV, Ovahe; HR, Hanga Roa; VA,Vaihu; AH, Akahanga.

• Indicates endemic species.

OJ. N • 5500

30

40

50

60

.--C70

80

90

100

:s Cl q

" '" \1 qq

~ ir~ " ~ " '"" " " '" q "~ ~ ~ ~ ::! " ~q q s: 0

FIGURE 2. Dendrograph showing indices of similarityfor the molluscan fauna of the seven sampled sectors onEaster Island.

two to Vaihu. Eighteen species representingother phyla were found with the mollusks.

The Sorensen similarity index shows thatfive sectors exhibited more than 50% similarity (Figure 2). Greatest similarity was between Hanga Nui and Vaihu (67%), andHanga Nui, Vaihu and Hanga Roa, and Akahanga (62-63%). In contrast, Vinapu andOvahe showed less similarity with the aboveareas (34%) and both showed a low index(35%).

The results obtained from the transects ofvertical distribution of the mollusks of therocky intertidal are shown in Figure 3. HangaRoa and Vaihu, both areas with gradualslopes, basaltic volcanic rock of similar com-

position, littoral pools, and patches of coral,are the most similar of the areas sampled.

Zonation

From the high-tide line to the low-tide line,organisms are arranged in horizons or zonesparallel to the coastline. These horizons arecharacterized by certain macrospecies that aredominant in number in each of the horizons,but that actually form a biological continuumfrom the high-tide line to the low-tide line.Three typical horizons are described.

The dominant species in the upper horizonwere the gastropod Nodilittorina pyramidalispascua and the barnacle Rehderella belyaeviZevina and Kurshakova. Nodilittorina (meanlength, 11.9 mm) reached an abundance of304 specimens per square meter in certain sites.The other dominant component, the balanidRehderella, covered an average of 26% of therock surface. At the lower reaches ofthe upperhorizon, the nerites Nerita morio and N. lirelataincreased in abundance both on and underrocks. As many as 52 specimens per squaremeter were counted. In the lower part of theupper horizon, under rocks, small specimens(mean length, 5.9 mm) of Planaxis akuana(724 specimens per square meter) were found,together with Nerita, the crab Cyclograpsuslongipes Stimpson, and the brittle starOphiocoma dentata Muller and Troschel. Anaverage of 84 specimens of varying sizes ofOphiocoma were counted per square meter.The brittle star preys on the gastropodPlanaxis.

In the middle horizon the dominant orga-


TABLE I (continued)




TellinamauiaDall x

Mactridaesp. x

AH

x



OJ. N • 5500

30

40

50

60

.--C70

80

90

100

:s Cl q

" '" \1 qq

~ ir~ " ~ " '"" " " '" q "~ ~ ~ ~ ::! " ~q q s: 0






Zonation





TABLE I (continued)




TellinamauiaDall x

Mactridaesp. x

AH

x



OJ. N • 5500

30

40

50

60

.--C70

80

90

100

:s Cl q

" '" \1 qq

~ ir~ " ~ " '"" " " '" q "~ ~ ~ ~ ::! " ~q q s: 0






Zonation




....=(ta-.0.e:.t:100'5".g-::t,o=o....,~2e-en:>;"en

I

io»zo

~'"

~L.p'ogropsus

Cypro.o

, Ee"r_ I

i1JJ.Comllmoceoe

POCi/iopora

{;.,/

~.•..

. !' .

-'. ~

C\- ~'C~

StypopodiUftl

t N_Oiloo £uc"'u'

t' /~

£UpIiCO

Lobophoro

Stoma,.flo

Sorgosum

HIGH TIDE ---LOW TIDE

':~';~~:, ....~"~-I-'

Conus

~'J.

11HllJim.do

Holothurio

""'i-.,

S,phonor,o

l.:r.~'"

3Ftlfurk/tM

-

Adil'lorio

~.'.,'~

PIOltiphOra

o @•Loso.o

(\

'-'

4Plonoltl$

Ophiocomo

QN.ri,o

NOtj,/,"ormo

<' / (I. I0,0 L " 7 _, ,.~ ) I •

(m)

1.0

0.5

FIGURE 3. Vertical distribution of mollusks and associated organisms in the rocky intertidal of Easter Island.

wo-..I

L.p'ogropsus

Cypraea,EC~/ro

r •IPoCilfoporo

StypopoeJiUftl

t N~.".~ £uc"'u',/~

Eupliea

HIGH TIDE __ LOW TIDE

Lobophoro

Holothurio

~.'."'i7/ff'

Pla.'pharoNodlf,"or",o

O.OL----.f----7'<-:-----,~-_T_+-_t_--+-

Opltiocomo

(m)

1.0

0.5


L.p'ogropsus

Cypraea,EC~/ro

r •IPoCilfoporo

StypopoeJiUftl

t N~.".~ £uc"'u',/~

Eupliea

HIGH TIDE __ LOW TIDE

Lobophoro

Holothurio

~.'."'i7/ff'

Pla.'pharoNodlf,"or",o

O.OL----.f----7'<-:-----,~-_T_+-_t_--+-

Opltiocomo

(m)

1.0

0.5


308

nisms were the chiton Plaxiphora and the coralPorites, and mollusks were less conspicuousthan the algae Ulva lactuca, Cladophora sp.,and Gelidium sp. The only live-collected bivalve, Lasaea, was found on fronds ofGelidium. The gastropod Dendropoma sp.was found cemented to the substrate. Plaxiphora was relatively abundant in crevices,and a maximum number of 24 specimens persquare meter was recorded. The errant polychaete Eurythoe complanata (pallas) and crabssuch as Petrolisthes coccineus (Owen) andxanthids were found under the rocks.

The most conspicuous component of thepools in this zone was the coral Poriteslobata. Small fish and eels (Moringuidae andMuraenidae) were seen under the coral heads.There was also a great abundance of algaesuch as Sargassum skottsbergii, Lobophoravariegata, and Halimeda opuntia in the pools.Specimens of the gastropods Conus, Euchelus,Euplica, Neothais, Nodochila, Stomatella, andStrombus, and, occasionally, individuals ofAplysia sp. (up to 800 g) were found amongthe algae. Another important biological component of this horizon was the sea cucumbersHolothuria difficilis and H. cinerascens, whichwere found on the bottom of the pools atmean densities of 701m 2

• Other organismsattached to the substrate included Actinariaand the hipponicid gastropods Antisabia andPilosabia.

At the lowest horizon, the most typicalmacrocomponent was the sea urchin Echinometra insularis Clark. This echinoid is a rockborer and builds marine "pots." Mean densities of 17 specimens per square meter wererecorded. Fifty-four percent of the "pots"contained other organisms such as paguridcrabs, nerites, polychaetes, turbellarians, smallspecimens of Plaxiphora, and Neothais. In theremaining 46% of the cavities, only Echinometra was found. The gastropod Cypraeacaputdraconis was collected in cavities. Crustose algae were found on rocks in neighboring areas. When density ofechinoids is low(less than 101m2

), algal cover increases. A fewspecimens of Dendropoma, Pocillopora, andEchinostrephus sp., another rock borer, werealso recorded in this horizon.

PACIFIC SCIENCE, Volume 43, October 1989

DISCUSSION AND CONCLUSIONS

The distribution of the 64 identified speciesof gastropods in the intertidal of Easter Island, and especially those of Nodilittorina,Cypraea, Plaxiphora, and Planaxis, supportRehder's (1980) conclusions on distribution.Thirty-nine percent of the intertidal mollusksrecorded are endemic, a figure close to that ofRehder's (1980) 42% for overall mollusk endemism. The high proportion of mollusks endemic to the intertidal on Easter Island alsosupports Vermeij's (1972) hypothesis that highintertidal organisms are specifically adaptedto the morphological and physiological requirements of the physical regime in whichthey live. Neritids and littorinids, for example,are particularly adapted to high temperatureand stresses of desiccation. .

Generally speaking, the pattern ofdistribution of the mollusks sampled is relativelyhomogeneous on the south, northeast, andnorthwest sectors of the island. The relativelylow similarity index (35%) for two sectors ofthe island, Ovahe and Vinapu, compared withan average index of 63% for the other fiveareas, may be influenced by the topographiccharacteristics of the sites, or can perhaps beexplained in terms of habitat (Kay 1979).Ovahe is a beach where rocks alternate withsandy areas, and the water in the intertidal hasa high sediment content that may hinder settlement on rocks. Vinapu is a narrow beachwith smooth, rounded edges. The physicalcharacteristics of both sectors are such thatonly a limited number of organisms can survive in these areas, where, as suggested byEleftheriou and Nicholson (1975), physicaldisturbance and severe hydrodynamic conditions provoke sediment instability.

The rocky intertidal is well known for zonation, the arrangement ofcommunities parallelto the coastline (Menge and Lubchenko 1981).Easter Island is no exception, although zonation is less obvious in some sectors of theisland than in others, as has been reported forTaboguilla, Panama (Lubchenko et al. 1984).

The occurrence of some mollusks can beexplained by the occurrence ofcertain types ofhabitat such as substrate or the occurrence of

308












308












Intertidal Distribution of Mollusks-OsORIO AND CANTUARIAS 309

algae. Some organisms are found only on basalt shores ('fermeij 1971). Others are foundonly where algae are abundant, as is Aplysia,the stomach contents of which include intertidal algae such as Hypnea, Laurencia, andSphacelaria (M. E. Ramirez, pers. comm.).

The occurrence of corals in the intertidal isremarkable. Scarce and isolated, corals do notform reefs around the island, probably because seawater temperatures are below theminimum tolerated by reef-building corals(Wells 1972), and perhaps also because of theisolation of the islands, the limited number ofhabitats (Randall and McCosker 1975), andthe rugged tectonic features and problematicoceanographic climate (Di Salvo 1985).

Several food webs have been identified inthe rocky intertidal at Easter Island. Polychaete, sipunculid, and gastropod food webswere recorded by Kohn (1978b), who identified Mitra flavocingulata preying on sipunculids; Neothais nesiotes feeding on Rehderellabelyaevi, Antisabia imbricata, and Dendropomasp.; and Pisania decapitata englerti preying onpolychaetes. Planaxis, with abundances typical of those reported by Houbrick (1987), ispreyed on by large numbers of Ophiocoma. Itis worth noting that Conus miliaris at EasterIsland (Kohn 1978a) has a microhabitat distribution in the intertidal of the western IndoPacific similar to that at Easter Island, reaching the same depths. Most specimens are foundassociated with algae, although Conus feedson polychaetes.

Comparison of the organisms present atEaster Island and those of rocky intertidalareas in the tropical Pacific and on the coastsof the Americas is shown in Table 2. As hasbeen pointed out by Vermeij (1971, 1973),Vermeij et al. (1983), and Kay (1979), thesame families and genera of mollusks, barnacles, echinoids, and corals occur in tropicalwaters around the world, but the species aredifferent. At Easter Island, the species arenoticeably different because of the high percentage of endemism among the mollusks.The fauna of Easter Island also differs in thatfewer species of mollusks occur in intertidalthan are recorded elsewhere: 14 molluscanspecies were recorded at Easter Island in con-

trast to an average of 20 in the tropical American intertidal areas and an average oDO in theintertidal areas of the Hawaiian Islands andthe northern Marianas. This finding is consistent with that of Santelices and Abbott(1988), who recorded relatively few species ofalgae in the intertidal. It is also noteworthythat members of the family Mytilidae do notform conspicuous mats as they do in Hawaiiand Pernambuco (Kay 1979, Vermeij andPorter 1971).

Although the population ofEaster lsland isrelatively small, the island has a long historyof human habitation, and the effects of thathistory are apparent. Cowries, for example,are virtually limited to the lowest horizon ofthe intertidal, but the occurrence of two specimens in the middle horizon suggests that thedistribution of Cypraea caputdraconis is, orhas been, wider than it is today.

ACKNOWLEDGMENTS

We thank professors N. Bahamonde, D.Soto, and E. Valenzuela for valuable suggestions and help with revision of the manuscript;L. Di Salvo for references; M. E. Ramirez, N.Rozbaczyl0, and M. Codoceo for identifyingalgae, polychaetes, and holothurians, respectively; L. Gonzalez, E. Villouta, A. San Martin, T. Pakarati, and A. Rirorroco for help inthe field; C. Fernadez for diagrams; M. Bustosfor technical assistance; and M. Cariceo fortyping. This work was supported financiallyby the Departamento Tecnico de Investigacion, Universidad de Chile.

LITERATURE CITED

BOONEN, J. 1897. Isla de Rapa Nui 0 de Pascua.Ensayo sobre Geografia Militar de Chile.Torno II. Imprenta Cervantes.

CASTILLA, J. c., and N. ROZBACZYLO. 1987.Invertebrados marinos de Isla de Pascua ySala y Gomez. Pages 191-215 in J. C. Castilla, ed. Islas Oce{micas Chilenas. Ed.Univ. Catolica de Chile.

CEA, E. A., and L. H. DI SALVO. 1982. Massexpulsion of Zooxanthellae by Easter Island corals. Pac. Sci. 36: 61-63.








ACKNOWLEDGMENTS


LITERATURE CITED











ACKNOWLEDGMENTS


LITERATURE CITED




TABLE 2

MOLLUSCAN SPECIES COMPOSITION OF TIlE INTERTIDAL OF EASTER ISLAND AND SOME TROPICAL AMERICAN AREAS AND PACIFIC ISLANDS GROUPS

w-oMARGARITA ISLAND, TABOGUILLA ISLAND,

FLORIDA KEYS VENEZUELA PANAMA NORTIlERN MARIANA(Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAllAN ISLANDS ISLANDS

EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Vermeij et al. 1983)

Upper HorizonNodilittorina Nodilittorina Nodilittorina

pyramidalis pascua hawaiensis pyramidalismillegrana

Littorina Littorina Littorina Littorinaziczac ziczac aspera pintado

modestaNerita Nerita Nerita Nerita Nerita Nerita

lirellata peloronta peloronta funiculata picea albicillamorio versicolor versicolor scabricosta guamensis

insculptamaximaplicata

Theodoxus 'i:lneglectus >

Tectarius Tectarius (J....tuberculatus muricatus "l:j....

Planaxis Planaxis Planaxis Planaxis (J

akuana lineatus labiosa niger t:fl(J

zonatus ....Echininus trI

Znodulosus (J

Acanthina .trIbrevidentata -<

Melampus 0a'

flavus~coffeus.j::o.

Detracia .wbulloides 0

Rehderella Tetraclita ('").....belyaevi 0

sp. (j

Onchidium(I)..,

verraculatum -\000\0

TABLE 2

MOLLUSCAN SPECIES COMPOSITION OF THE INTERTIDAL OF EASTER ISLAND AND SOME TROPICAL AMERICAN AREAS AND PACIFIC ISLANDS GROUPS

w-o

MARGARITA ISLAND, TABOGUILLA ISLAND,FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA

(Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAIIAN ISLANDS ISLANDSEASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Verrneij et al. 1983)

Upper Horizon

Nodilittorina Nodilittorina Nodilittorinapyramidalis pascua hawaiensis pyramidalis

millegranaLittorina Littorina Littorina Littorina

ziczac ziczac aspera pintadomodesta

Nerita Nerita Nerita Nerita Nerita Neritalirellata peloronta peloronta funiculata picea albicillamorio versicolor versicolor scabricosta guamensis


Theodoxus '"Cneglectus >





Znodulosus (J


Melampus 0a'




sp. (j'

Onchidium(p....


TABLE 2

MOLLUSCAN SPECIES COMPOSITION OF THE INTERTIDAL OF EASTER ISLAND AND SOME TROPICAL AMERICAN AREAS AND PACIFIC ISLANDS GROUPS

w-o

MARGARITA ISLAND, TABOGUILLA ISLAND,FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA

(Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAIIAN ISLANDS ISLANDSEASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Verrneij et al. 1983)

Upper Horizon

Nodilittorina Nodilittorina Nodilittorinapyramidalis pascua hawaiensis pyramidalis

millegranaLittorina Littorina Littorina Littorina

ziczac ziczac aspera pintadomodesta

Nerita Nerita Nerita Nerita Nerita Neritalirellata peloronta peloronta funiculata picea albicillamorio versicolor versicolor scabricosta guamensis


Theodoxus '"Cneglectus >





Znodulosus (J


Melampus 0a'




sp. (j'

Onchidium(p....


TABLE 2 (continued) ....S.'"MARGARITA ISLAND, TABOGUILLA ISLAND,..,5:FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA e:.(Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAllAN ISLANDS ISLANDS~EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Vermeij et al. 1983)OJ>....:::!.

Middle Horizon 0"c::

Diodora g.listeri ::3

Fissurella Fissurella 0.....,nimbosa virescens

~Raliotis 2-

varia a-Cellana Cellana OJ>

~

exarata toreumaOJ>

IPatella 0flexuosa on

0Notacmaea 5sp. >Stomatella Z

planulata 0()Nerita >

tessellata Z""l

versicolor c:::Dendropoma ~

spp. >onSerpulorbis

variabilisAntisabia Antisabia

Joliacea Joliaceaimbricata imbricata

Pilosabia Pilosabiatrigona pilosus

Neothais Neothaisnesiotes harpa

Thais Thais Thais Thaisrusticus melones intermedia armigera

intermediaPurpura Purpura

aperta persicaMorula Morula

granulata biconicaw

uva granulata --uva

wTABLE 2 (continued) -N

MARGARITA ISLAND, TABOGUILLA ISLAND,

FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA

(Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAllAN ISLANDS ISLANDS


Drupa Drupamorum morumricina ricina

rubusidaeusCantharus

tinctusOnchidium

floridianumSmaragdinella Smaragdinella

calyculata calyculataSiphonaria Siphonaria Siphonaria Siphonaria Siphonaria

pascua alternata gigas normalis siriuspectinata cf. guamensis

Melampuspascua

Mytilus Perna Brachidontes Brachidontes "'Cexustus perna semilaevis crebristriatus >

Modiola (")-capax "rj-Isognomon Ostrea (")

alala spp. tIJ

chemnitziana Ceratozona(").....

sp. tTlZ

Plaxiphora Acanthopleura Chiton Acanthochiton Acanthochiton (")mercatoria granulata stokesi armata gemmata .tIl

viridis -<Chthamalus 0

stellatus [Tetraclita (1)

squamosa ~.w

Lower Horizon 0Diodora Diodora Diodora Diodora Diodora 0...

granifera antillarum sp. granifera granifera 0cr"

Fissurella Fissurella (1)..,nimbosa longifissa -\0

virescens 00\0

wTABLE 2 (continued)

....tv

MARGARITA ISLAND, TABOGIDLLA ISLAND,






tinctusOnchidium

fioridianumSmaragdinella Smaragdinella

ca/ycu/ata ca/ycu/ataSiphonaria Siphonaria Siphonaria Siphonaria Siphonaria

pascua a/ternata gigas normalis siriuspectinata cf. guamensis

Me/ampuspascua

Mytilus Perna Brachidontes Brachidontes "Cexustus perna semilaevis crebristriatus >

Modio/a ()....capax "Ij....

Isognomon Ostrea ()

a/ata spp. tZl

chemnitziana Ceratozona()....

sp. t'I1Z

P/axiphora Acanthop/eura Chiton Acanthochiton Acanthochiton ()mercatoria granu/ata stokesi armata gemmata .t'I1

viridis <:Chthama/us 0

2"stellatus S

Tetraclita <11

""'-squamosa .wLower Horizon 0

Diodora Diodora Diodora Diodora Diodora 0


Fissurella Fissurella <11..,nimbosa /ongifissa ....

\0virescens 00

\0

wTABLE 2 (continued)

....tv

MARGARITA ISLAND, TABOGIDLLA ISLAND,






tinctusOnchidium

fioridianumSmaragdinella Smaragdinella

ca/ycu/ata ca/ycu/ataSiphonaria Siphonaria Siphonaria Siphonaria Siphonaria

pascua a/ternata gigas normalis siriuspectinata cf. guamensis

Me/ampuspascua

Mytilus Perna Brachidontes Brachidontes "Cexustus perna semilaevis crebristriatus >

Modio/a ()....capax "Ij....

Isognomon Ostrea ()

a/ata spp. tZl

chemnitziana Ceratozona()....

sp. t'I1Z

P/axiphora Acanthop/eura Chiton Acanthochiton Acanthochiton ()mercatoria granu/ata stokesi armata gemmata .t'I1

viridis <:Chthama/us 0

2"stellatus S

Tetraclita <11

""'-squamosa .wLower Horizon 0

Diodora Diodora Diodora Diodora Diodora 0


Fissurella Fissurella <11..,nimbosa /ongifissa ....

\0virescens 00

\0

.....::s...(l)....

TABLE 2 (continued) 5:e:.

MARGARITA ISLAND, TABOGlnLLAISLAND, 0FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA ~.

(Stephenson and (Rodriguez 1959, (Lubchenko et ai. HAWAIIAN ISLANDS ISLANDS::!.cr"

EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Verrneij et ai. 1983) c::o.0

Cellana::s0

sandwicensis....,

Tegula ~

fasciata 2-2"

Cypraea Strombus Cypraea Cypraea '";>;"caputdraconis gigas caputserpentis caputserpentis '"

Petaloconchus Ikeenae 0

'"Thais Thais 0~

haemastoma melones 0A canthina >

brevidentata 8Siphonaria (J

>maura ZArca Chama Chama

..,C

barbatia echinata iostoma >umbonata Isognomon Isognomon ~

>incisum incisum en

Ischnochiton Chiton Tonicialimaciformis tuberculatus forbesi

Porites Porites Poriteslobata spp. sp.

Poci/lopora Millepora Acropora Poci/lopora Poci/lopora Poci/loporasp. sp. sp. damicornis meandrina meandrina

Meandrinasp.

Balanusinexpectatus

Chthamalussp.

Echinometra Echinometra Echinometra Echinometra Echinometra Echinometrainsularis lucunter lucunter vanbranti mathaei sp.

w.....w

314

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vertical distribution ofmollusks on the rocky …...vertical distribution ofmollusks on the rocky...

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