biogeography of reef-building corals in the mariana and ...guammarinelab.org/publications/randall...

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Nat. Hist. Res., Vol. 3 No. 2: 193-210, March 1995

Biogeography of Reef-Building Corals in the Marianaand Palau Islands in Relation to Back-Arc Riftingand the Formation of the Eastern Philippine Sea

Richard H. Randall

University of Guam, Marine Laboratory U.O.G. StationMangilao, Guam 96923

Abstract An interesting aspect of the scleractinian reef-building fauna of the Mariana Arc Islands istheir relatively low diversity (ca. 254 species) when compared to other Northwest Pacific regions, suchas the Phillippine Islands (ca. 411 spp.), Ryukyu and Japan Islands (ca. 381 spp.), Caroline Islands (ca.395 spp.), and Marshall Islands (ca. 300 sp.). Out of these relatively high coral diversity island groupsthe Palau Archipelago in the Western Caroline Islands has a reef-building coral fauna of about 385species, and is especially interesting for comparison with the Mariana Arc coral fauna because of theislands similar size and age, but different geologic histories.

According to current plate tectonic hypotheses the Mariana Forearc was once part of the Palau-Kyushu Ridge, from where it has been displaced to its present position at the eastern margin of thePhilippine Sea by two episodes of back-arc rifting and basin development followed by active arcvolcanism. A model is developed which suggests that during part of the back-arc basin formation phaseof the first episode the migrating forearc may have been drowned to a depth that precluded the presenceof hermatypic reef-building corals. Subsequently, during the active volcanic arc phase of the firstepisode, hermatypic reef-building corals could then be recolonized on shoaling West Mariana Ridgehighs. The absence of marginal sea formation along the southern part of the Palau-Kyushu Ridgealso suggests that shoal-water conditions and the presence of reef-building hermatypic corals along thePalau Archipelago was not interrupted during the formation of the Eastern Philippine Sea. If the MarianaForearc was emergent during its migration from the Palau-Kyushu Ridge it is hypothesized that thecoral fauna would be more similar to that of the Palau Archipelago. Evidence is given for the abovemodel based upon the timing and stratigraphic sequence of carbonate and volcanic units on thePalau-Kyushu Ridge and Mariana Forearc and Western Mariana remnant arc ridges, Deep Sea DrillingProgram data, and characteristics of the present hermatypic reef-building coral faunas of the PalauArchipelago and Mariana Forearc.

Keywords: hermatypic corals, biogeography, Eastern Philippine Sea, Mariana Islands, Palau Isl-ands.

One of the most interesting aspects ofnatu-ral history is the distribution of plants andanimals, both in a local context at communityand ecosystem levels, and more broadly at geo-graphic levels. Biogeography is particularlyinteresting at geographic scales because itinvokes pathways and mechanisms by whichorganisms become distributed within theirranges. In this paper a brief review of reef-building coral diversity within the NorthwestPacific Ocean is given, followed by a focus onthe biogeography of such corals in the Marianaand Palau Islands in relation to back-arc riftingand the formation of the Eastern PhilippineSea (Figs. 1 and 2).

Approach to the Concept of Coral Diversity

Since diversity can be measured in a numberof ways, the concept of the term as used here issimply the number of taxa within a definedgeographic region. Reef-building coral diversi-ty of a geographic region is generally related tothe amount of collecting effort and the degreeto which all the coral habitats have been sam-pled. As an example, there may have been agreat amount of collecting effort from shallow-water habitats within a certain geographicregion, but until the deeper-water habitats arealso sampled the diversity estimates will gener-ally be underestimated. Before scuba was usedas an aid to sampling, estimates of reef-

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Fig. 1. Bathymetric map of the Philippine Sea and surrounding areas. Numbers refer to Deep-SeaDrilling coring sites. Contour interval=3000 meters. After Chase et al. (1971).

building coral diversity were generally basedupon shallow-water collections, occasionallyaugmented with limited ship-board dredgedspecimens, that generally resulted in an under-estimate of overall actual diversity. In the lastdecade or so, earlier coral diversity estimates

for an increasing number of geographic loca-tions have been greatly revised from an overallincreased sampling effort as well as from scubasampling from deeper water habitats.

Reef-building coral diversity estimates usedin this paper are based upon the authors collec-

Biogeography of reef-building corals in the Mariana and Palau Islands

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tions for the Mariana and Caroline Islands,partly upon the authors collections and litera-ture reviews for the Marshall Islands, and forthe most part upon relatively recent compre-hensive reviews of the literature and some col-lections by the author for Japan and RyukyuIslands and Philippine Islands.

Table 1 gives an estimate of both the collect-ing effort and the degree to which the reef-building coral habitats have been sampledwithin the Mariana, Caroline, and MarshallIsland groups. A collecting station, as definedhere, indicates a distinct uniform habitat andgeographic location from which one or more

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Table 1. Number of collecting stations, number of specimens collected at the collecting stations, percent of coral habitats sampled,and percent of collecting station effort for various islands within the Southern Marianas, Northern Marianas, Eastern Caroline,Western Caroline, and Marshall Island groups.

A B C DGeographic Collecting Number of Percent of Percent of

Location Stations Specimens Coral Habitats Collectingfor each Collected Sampled StationIsland Effort

Southern Mariana Islands1. Guam 1724 9771 95 74.22. Rota 116 253 10 5.03. Aguijan 16 79 5 0.74. Tinian 121 594 20 5.25. Saipan 333 1421 50 14.36. Farallon de Medinella 6 94 2 0.37. Galvez Bank 7 164 3 0.38. Santa Rosa Reef 2 12 <1 0.1

Totals 2325 12388

Northern Mariana Islands1. Esmerelda Bank 1 1 <1 0.52. Anatahan 29 364 10 13.93. Sarigan 6 33 5 2.94. Zealandia Bank 2 16 10 1.05. Guguan 20 115 7 9.66. Alamagan 2 9 <1 1.07. Pagan 78 428 20 37.38. Agrihan 17 146 7 8.19. Asuncion 8 58 3 3.8

10. Maug Islands 46 280 15 22.011. Farallon de Pajaros 6 35 <2 2.9

Totals 209 1485 Totals for all the Mariana Islands 2534 13873

Eastern Caroline Islands1. Ulithi Atoll 25 116 3 4.62. West Fayu Atoll 24 86 2 4.43. Woleai Atoll 8 33 1 1.24. Truk Islands 261 1545 10 48.25. Ponape 196 1054 7 36.26. Kosrae 28 324 4 5.2

Totals 542 3158

Western Caroline Islands1. Palau Islands 264 1541 7 77.22. Yap Islands 78 402 5 22.8

Totals 342 1943 Totals for all of Caroline Islands 884 5101

Marshall Islands1. Kwajalein Atoll 31 234 5 30.72. Eniwetok Atoll 10 528 7 69.3

Totals 101 762

corals have been collected, but does not includestations from which quantitative data or spe-cies lists only have been compiled. Each spe-cies listed from a geographic area in Table 2 isrepresented by one or more voucher specimensdeposited in the University of Guam Marine

Laboratory Museum collections. The amountof time spent at each collecting station rangedfrom 10 to 60 minutes, with an average ofabout 20 minutes. The number of coral speci-mens collected is the total tabulated from allthe collecting stations for an island. The


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amount of collecting station effort for eachisland (Table 1, Column D) is given as a relativepercent of all the stations of an island group,and the amount of coral habitat sampled (Table1, Column C) is given as an estimate of thepercent of an islands total area occupied byreef-building corals from which specimenshave been collected. Table 1 shows consider-able variation in the relative percentage of col-lecting station effort and percentage of coralhabitat sampled between island groups as wellas between islands within an island group. Ingeneral, islands that are more easily accessedby commercial transportation or have marineresearch institutions located on them havehigher numbers of collecting stations and col-lected specimens, especially from Guam wherethe author has resided and been collectingcorals since 1965. With greater collectioneffort it is expected that more new speciesrecords would be found in large island groupsthat have had a low percentage of their poten-tial coral habitats collected from, such as Palau,and the least number of new species recordsfrom islands where a significant percentage ofthe coral habitats have been sampled, such asGuam and Saipan.

Distribution of Reef-Building Corals withinthe Northwest Pacific Ocean

and Philippine Sea

Recent comprehensive reviews of reef-building coral diversity within the majorisland groups of the Northwest Pacific Oceanand Philippine Sea list 381 species and 76genera from Japan and Ryukyu Islands (Veron,1992; Nishihira, 1988), 411 species and 77genera from the Philippine Islands (Veron andHodgson, 1989), 395 species and 69 generafrom the Eastern and Western Caroline Islands(collections made by Randall and others from1966–1994), ca. 300 species and 62 genera fromthe Marshall Islands (Wells, 1954; and collec-tions made by Randall and others from 1970–1976), and 253 species and 56 genera from theMariana Islands (Randall and Myers, 1983; andcollections made by Randall and others from1965–1994). An interesting aspect of the reef-building coral fauna of the Mariana Islands istheir significantly lower diversity when com-

pared to other Northwest Pacific Ocean andPhilippine Sea island groups. The MarianaIslands appears as a lower coral diversity ano-maly surrounded by other higher coraldiversi-ty island groups. A comparison of coralspecies from the Northwest Pacific Ocean andPhilip-pine Sea island groups also reveal that theMariana fauna, as well as that of the Carolineand Marshall Islands, are for the most part anattenuation of the high-diversity WesternPacific region. There are very few endemicreef-building coral species found east of thePhilippine Islands in the North Pacific.

Biogeography of the Reef-Building Corals ofthe Mariana and Palau Islands in Relation

to the Formation of the EasternPhilippine Sea

Out of the relatively high coral diversityisland groups within the Northwest PacificOcean and Philippine Sea, the Palau Islands inthe Western Caroline Islands has a reef-building coral fauna of about 385 species and66 genera. The Palau fauna is especially inter-esting for comparison with the less diverseMariana coral fauna of about 254 species and56 genera, because of the two island groupssomewhat similar size, origin, age, and relatedbut different geologic histories.

Table 2 shows that 244 reef-building coralspecies are common to both the Palau andMariana Islands, and that all 56 genera collect-ed from the Mariana Islands are found in thePalau Islands. There are 141 coral species col-lected from Palau that have not been collectedin the Marianas, and ten species collected fromthe Marianas that have not been collected inPalau. In regard to the ten Mariana coral spe-cies that have not been collected from Palau:two are pocilloporid species that probablyoccur in Palau if the proper high-energy sea-ward reef slopes were better investigated; twoare Madracis species, one of which is rare andhas only been collected from a single stationfrom Guam; one is an undescribed but commonramose Coscinaraea species dredged from thelower (ca. 100 m) seaward reef slopes from anumber of Mariana Islands stations, and proba-bly occurs in Palau if similar habitats weredredged; four are widespread cycloserid and

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Table 2. List of coral species collected from the Palau Islands, Southern Mariana Forearc Islands, andNorthern Marianna Volcanic Arc Ridge Islands.

Palau Southern NorthernCoral Order, Family and Species Islands Mariana Mariana

Islands IslandsOrder SCLERACTINIAFamily ASTROCOENIIDAE

Stylocoeniella armata (Ehrenberg, 1834) x x xStylocoeniella guentheri (Bassett-Smith, 1890) x x x

Family THAMNASTERIIDAEPsammocora contigua (Esper, 1797) x xPsammocora digitata Edwards & Haime, 1851 x x xPsammocora explanulata van der Horst, 1922 x xPsammocora haimeana Edwards & Haime, 1851 x x xPsammocora nierstraszi van der Horst, 1921 x x xPsammocora obtusangula (Lamarck, 1816) x xPsammocora profundacella Gardiner, 1898 x x xPsammocora stellata (Verrill, 1866) x xPsammocora superficiales Gardiner, 1898 x xPsammocora sp. 1 (collines) x x xPsammocora sp. 2 (columnar, pink) x xPsammocora sp. 3 (columnar, brown) x

Family POCILLOPORIDAESeriatopora aculeata Quelch, 1886 x xSeriatopora caliendrum Ehrenberg, 1834 x xSeriatopora hystrix Dana, 1846 x x xSeriatopora sp. 1 (thick blunt tips) x xStylophora mordax (Dana, 1846) x x xStylophora pistillata Esper, 1797 xPalauastrea ramosa Yabe & Sugiyama, 1941 xPocillopora ankeli Sheer & Pillai, 1974 x x xPocillopora damicornis (Linnaeus, 1758) x x xPocillopora dame Verrill, 1864 x x xPocillopora elegans Dana, 1846 x x xPocillopora eydouxi Edwards & Haime, 1860 x x xPocillopora ligulata Dana, 1846 x x xPocillopora setchelli Hoff meister, 1929 x x xPocillopora meandrina Dann, 1846 x x xPocillopora verrucosa Edwards & Haime, 1860 x x xPocillopora woodjonesi Vaughan, 1918 x x xPocillopora sp. 1 (nodular branching) xPocillopora sp. 2 (compact branching) xMadracis asanoi Yabe & Sugiyama, 1941 xMadracis kirbyi Veron & Pichon, 1976 xMadracis palaoensis Yabe & Sugiyama, 1936 x xMadracis sp. 1 (small button) x

Family ACROPORIDAEAcropora (A.) abrotanoides (Lamarck, 1816) x xAcropora (A.) aculeus (Dana, 1846) x xAcropora (A.) acuminata (Verrill, 1864) x xAcropora (A.) aspera (Dana, 1846) x xAcropora (A.) austera (Dana, 1846) xAcropora (A.) azurea Veron & Wallace, 1984 x x xAcropora (A.) bushyensis Veron & Wallace, 1984 xAcropora (A.) carduus (Dana, 1846) xAcropora (A.) cerealis (Dana, 1846) x x xAcropora (A.) clathrata (Brook, 1891) xAcropora (A.) cytherea (Dana, 1846) x


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Table 2. (continued)


Islands IslandsAcropora (A.) dendrum (Bassett-Smith, 1890) xAcropora (A.) digitifera (Dana, 1846) x x xAcropora (A.) dispar Nemenzo, 1967 xAcropora (A.) divaricata (Dana, 1846) xAcropora (A.) echinata (Dana, 1846) xAcropora (A.) elseyi (Brook, 1892) xAcropora (A.) florida (Dana, 1846) x xAcropora (A.) formosa (Dana, 1846) x xAcropora (A.) gemmifera (Brook, 1892) x x xAcropora (A.) granulosa (Edwards & Haime, 1860) x xAcropora (A.) grandis (Brook, 1892) xAcropora (A.) hebes (Dana, 1846) x xAcropora (A.) horrida (Dana, 1846) xAcropora (A.) humilis (Dana, 1846) x x xAcropora (A.) hyacinthus (Dana, 1846) xAcropora (A.) irregularis (Brook, 1892) x x xAcropora (A.) kyirstyae Veron & Wallace, 1984 xAcropora (A.) longacyathus (Edwards & Haime, 1860) x xAcropora (A.) loripes (Brook, 1892) x x xAcropora (A.) lovelli Veron & Wallace, 1984 x xAcropora (A.) lutkeni Crossland, 1952 x xAcropora (A.) microphthalma (Verrill, 1869) xAcropora (A.) millepora (Ehrenberg, 1834) xAcropora (A.) monticulosa (Bruggemanni, 1879) x x xAcropora (A.) multiacuta Nemenzo, 1967 x xAcropora (A.) nana (Studer, 1878) xAcropora (A.) nasuta (Dana, 1846) x x xAcropora (A.) nobilis (Dana, 1846) xAcropora (A.) ocellata (Klunzinger, 1897) x x xAcropora (A.) palmerae Wells, 1954 x x xAcropora (A.) pulchra (Brook, 1891) xAcropora (A.) quelchi (Brook, 1893) x x xAcropora (A.) rambleri (Bassett-Smith, 1890) x x xAcropora (A.) robusta (Dana, 1846) xAcropora (A.) samoensis (Brook, 1891) xAcropora (A.) secale (Studer, 1878) x xAcropora (A.) selago (Studer, 1878) x x xAcropora (A.) smithi (Brook, 1893) x x xAcropora (A.) spicifera (Dana, 1846) xAcropora (A.) striata Verrill, 1866 x xAcropora (A.) studeri (Brook, 1893) x xAcropora (A.) subglabra (Brook, 1891) xAcropora (A.) surculosa (Dana, 1846) x x xAcropora (A.) tenella (Brook, 1892) xAcropora (A.) tenuis (Dana, 1846) x x xAcropora (A.) teres (Verrill, 1866) x xAcropora (A.) valenciennesi (Edwards & Haime, 1860) xAcropora (A.) valida (Dana, 1846) x x xAcropora (A.) vaughani Wells, 1954 x xAcropora (A.) verweyi Veron & Wallace, 1984 x xAcropora (A.) virgata (Dana, 1846) x xAcropora (A.) yongei Veron & Wallace, 1984 xAcropora (A.) sp. 1 xAcropora (A.) sp. 2 x

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Islands IslandsAcropora (A.) sp. 3 xAcropora (A.) sp. 4 xAcropora (A.) sp. 5 xAcropora (A.) sp. 6 x xAcropora (A.) sp. 7 (thick branch) x xAcropora (I.) brueggemanni (Brook, 1893) xAcropora (I.) cuneata (Dana, 1846) xAcropora (I.) palifera (Lamarck, 1816) x x xAnacropora forbesi Ridley, 1884 xAnacropora matthaii Pillai, 1973 xAnacropora puertogalerae Nemenzo, 1964 xAnacropora spinosa Rehberg, 1892 xAnacropora sp. 1 xAstreopora eliptica Yabi & Sugiyama, 1941 x x xAstreopora gracilis Bernard, 1896 x x xAstreopora listeri Bernard, 1896 x xAstreopora moretonensis Veron & Wallace, 1984 xAstreopora myriophthalma (Lamarck, 1816) x x xAstreopora ocellata Bernard, 1896 x x xAstreopora randalli Lamberts, 1890 x x xMontipora acanthella Bernard, 1897 x xMontipora angulata (Lamarck, 1816) xMontipora berryi Hoffmeister, 1925 x x xMontipora caliculata (Dana, 1846) x x xMontipora colei Wells, 1954 x x xMontipora danae Edwards & Haime, 1851 x xMontipora digitata (Dana, 1846) xMontipora edwardsi Bernard, 1897 xMontipora efflorescens Bernard, 1897 xMontipora ehrenbergii Verrill, 1875 x x xMontipora elschneri Vaughan, 1918 x x xMontipora cf. equituberculata Bernard, 1897 x xMontipora floweri Wells, 1954 x x xMontipora foliosa (Pallas, 1766) x xMontipora foveolata (Dana, 1846) x x xMontipora fragilis Quelch, 1886 xMontipora gaimardi Bernard, 1897 xMontipora granulosa Bernard, 1897 x xMontipora grisea Bernard, 1897 x x xMontipora hirsuta Nemenzo, 1967 (non Bernard) xMontipora hispida (Dana, 1846) xMontipora hoffmeisteri Wells, 1954 x x xMontipora incrassata (Dana, 1846) xMontipora informis Bernard, 1897 xMontipora lobulata Bernard, 1897 x x xMontipora monasteriata (Forskål, 1775) x x xMontipora cf. planiuscula (Dana, 1846) x x xMontipora pulcherrima Bernard, 1897 x xMontipora socialis Bernard, 1897 x x xMontipora stellata Bernard, 1897 xMontipora tuberculosa (Lamarck, 1816) x x xMontipora turgescens Bernard, 1897 xMontipora undata Bernard, 1897 xMontipora venosa (Ehrenberg, 1834) x x x


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Islands IslandsMontipora verrilli Vaughan, 1907 x x xMontipora verrucosa (Lamarck, 1816) x x xMontipora sp. 1 (green spine) x x xMontipora sp. 2 (ramose tuber.) xMontipora sp. 3 (Pago) x x xMontipora sp. 4 (Ramose pap.) xMontipora sp. 5 (thick branch) x x xMontipora sp. 6 (spiny grey) x

Family AGARICIIDAEPavona cactus (Forskål, 1775) x xPavona clavus (Dana, 1846) x x xPavona decussata (Dana, 1846) x xPavona difflens (Lamarck, 1816) x x xPavona divaricata (Lamarck, 1816) x xPavona duerdeni Vaughanm, 1907 x x xPavona explanulata (Lamarck, 1816) x xPavona frondifera (Lamarck, 1816) xPavona minuta Wells, 1954 x x xPavona maldivensis (Gardiner, 1905) x x xPavona varians Verrill, 1864 x x xPavona venosa (Ehrenberg, 1834) x x xPavona sp. 1 (collines) x x xPavona sp. 2 (white dot) x x xPavona sp. 3 (monticules) x x xGardineroseris planulata (Dana, 1846) x x xCoeloseris mayeri Vaughan, 1918 xLeptoseris explanata Yabe & Sugiyama, 1941 x x xLeptoseris foliosa Dineson, 1980 x xLeptoseris gardineri van der Horst, 1921 x xLeptoseris hawaiiensis Vaughan, 1907 x x xLeptoseris incrustans (Quelch, 1886) x x xLeptoseris mycetoseroides Wells, 1954 x x xLeptoseris scabra Vaughan, 1907 x x xLeptoseris solida (Quelch, 1886) x x xLeptoseris papyracea (Dana, 1846) x xLeptoseris yabei (Pillai & Scheer, 1976) xLeptoseris sp. 1 (pink) x xLeptoseris sp. 2 (cones) xPachyseris rugosa (Lamarck, 1816) xPachyseris speciosa (Dana, 1846) x x x

Family SIDERASTREIDAECoscinaraea columna (Dana, 1846) x x xCoscinaraea exesa (Dana, 1846) xCoscinaraea sp. 1 (ramose) x x

Family FUNGIIDAECycloseris costulata Ortmann, 1889 x x xCycloseris cyclolites Lamarck, 1816 x xCycloseris hexagonalis Edwards & Haime, 1848 x xCycloseris sinensis Edwards & Haime, 1851 xCycloseris tenuis Dana, 1846 xCycloseris vaughani (Boschma, 1923) xDiaseris fragilis Alcock, 1893 x xDiaseris distorta Michelin, 1842 xFungia (F.) fungites (Linnaeus, 1758) x x x

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Islands IslandsFungia (V.) concinna Verrill, 1864 x x xFungia (V.) granulosa Klunzinger, 1879 x xFungia (V.) repanda Dana, 1846 x xFungia (V.) spinifera Claereboudt & Hoeksema, 1987 x xFungia (D.) danai Edwards & Haime, 1851 x xFungia (D.) horrida Dana, 1846 x xFungia (D.) scabra Doderlein, 1901 xFungia (D.) scruposa Klunzinger, 1879 xFungia (P.) paumotensis Stutchbury, 1833 x xFungia (L.) scutaria Lamarck, 1801 x x xHelipfungia actinijormis (Quoy & Gaimard, 1833) xCtenactis albateutaculata Hoeksema, 1989 x xCtenactis echinata (Pallas, 1766) x xCtenactis crassa (Dana, 1846) xHerpolitha limax (Esper, 1797) x x xHerpolitha weberi (van der Horst, 1921) x xPolyphyllia talpina (Lamarck, 1801) x xSandalolitha dentata Quelch, 1884 x xSandalolitha robusta (Quelch, 1886) x x xLithophyllon undulatum Rehberg, 1892 xLithophyllon mokai Hoeksema, 1989 xPodabacia crustacea (Pallas, 1766) x xPodabacia sp. 1 x

Family PORITIDAEPorites (P.) annae Crossland, 1952 x xPorites (P.) australiensis Vaughan, 1918 x x xPorites (P.) cylindrica Dana, 1846 x xPorites (P.) densa Vaughan, 1918 xPorites (P.) eridani Umbgrove, 1940 x x xPorites (P.) cf. evermanni Vaughan, 1907 xPorites (P.)lichen Dana, 1846 x x xPorites (P.) lobata Dana, 1846 x x xPorites (P.)lutes Edwards & Haime, 1860 x x xPorites (P.) murrayensis Vaughan, 1918 x x xPorites (P.) cf. myrmidonensis Veron, 1985 xPorites (P.) nigrescens Dana, 1846 xPorites (P.) solida (Forskål, 1775) x xPorites (P ) stephensoni Crossland, 1952 x x xPorites (P.) superfusa Gardiner, 1898 x x xPorites (P.) sp. 1 (nodular) x x xPorites (P.) sp. 2 (spiny coen.) xPorites (P.) sp. 3 (lumpy yell.) x x xPorites (S.) convexa Verrill, 1864 x x xPorites (S.) horizontalata Hoff meister, 1925 x x xPorites (S.) rus (Forskål, 1775) x x xPorites (S.) sp. 1 (encrusting) x xPorites (N.) sillimaniana Nemenzo, 1976 xPorites (N.) vaughani Crossland, 1952 x xPorites (N.) sp. 1 (ramose) xStylaraea punctata Klunzinger, 1879 x xGoniopora columna Dana, 1846 x x xGoniopora djiboutiensis Vaughan, 1907 x xGoniopora eclipsensis Veron & Pichon, 1982 x x xGoniopora fruiticosa Saville-Kent, 1893 x x x


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Islands IslandsGoniopora lobata Edwards & Haime, 1860 x x xGoniopora minor Crossland, 1955 x x xGoniopora pandoraensis Veron & Pichon, 1982 x xGoniopora somaliensis Vaughan, 1907 x x xGoniopora stokesi Edwards & Haime, 1851 xGoniopora tenuidens Quelch, 1886 x x xGoniopora cf. traceyi Wells, 1954 xAlveopora allingi Hoffmeister, 1925 x x xAlveopora fenestrata (Lamarck, 1816) x xAlveopora spongiosa Dana, 1846 xAlveopora superficiales Sheer & Pillai, 1976 x x xAlveopora verrilliana Dana, 1872 x xAlveopora virdis Quoy & Gaimard, 1833 x x xAlveopora sp. 1 (small calices) x

Family FAVIIDAECaulastrea echinulata (Edwards & Haime, 1849) xCaulastrea furcata Dana, 1846 xCaulastrea tumida Matthai, 1928 xCaulastrea sp. 1 (fused calices) xBarabattoia amicorum (Edwards & Haime, 1850) xFavia danae Verrill, 1872 x xFavia favus (Forskål, 1775) x x xFavia helianthoides Wells, 1954 x x xFavia laxa (Klunzinger, 1879) xFavia lizardensis Veron, Pichon & Wijsman-Best, 1977 xFavia maritima Nemenzo, 1971 x xFavia matthaii Vaughan, 1918 x x xFavia pallida (Dana, 1846) x x xFavia rotumana (Gardiner, 1899) x x xFavia rotundata Veron, Pichon & Wijsman-Best, 1977 xFavia stelligera (Dana, 1846) x x xFavia sp. 1 (small calice) xFavites abdita (Elks & Solander, 1786) x x xFavites chinensis (Verrill, 1866) xFavites complanata (Ehrenberg, 1834) xFavites flexuosa (Dana, 1846) x x xFavites halicora (Ehrenberg, 1834) xFavites pentagons (Esper, 1794) xFavites russelli (Wells, 1954) x x xGoniastrea aspera Verrill, 1865 xGoniastrea australensis (Edwards & Haime, 1857) xGoniastrea edwardsi Chevalier, 1971 x x xGoniastrea favulus (Dana, 1846) xGoniastrea palauensis (Yabe, Sugiyama & Eguchi, 1936) xGoniastrea pectinata (Ehrenberg, 1834) x x xGoniastrea retiformis (Lamarck, 1816) x x xGoniastrea sp. 1 xLeptoria phrygia (Elks & Solander, 1786) x x xPlatygyra daedalea (Ellis & Solander, 1786) x x xPlatygyra lamellina (Ehrenberg, 1834) xPlatygyra pini Chevalier, 1975 x x xPlatygyra sinensis (Edwards & Haime, 1849) xPlatygyra cf. verweyi Wijsman-Best, 1976 xOulophyllia crisps (Lamarck, 1816) x x x

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Islands IslandsOulophyllia sp. 1 xMontastrea annuligera (Edwards & Haime, 1849) xMontastrea curta (Dana, 1846) x x xMontastrea magnistellata Chevalier, 1971 x x xPlesiastrea versipora (Lamarck, 1816) x x xDiploastrea heliopora (Lamarck, 1816) x xLeptastrea bottae (Edwards & Haime, 1849) x x xLeptastrea cf. immersa Klunzinger, 1879 x x xLeptastrea pruinosa Crossland, 1952 xLeptastrea purpurea (Dana, 1846) x x xLeptastrea transversa Klunzinger, 1979 x x xCyphastrea chalcidicum (Forskål, 1775) x x xCyphastrea microphthalma (Lamarck, 1816) x x xCyphastrea serailia (Forskål, 1775) x x xCyphastrea cf. ocellina (Dana, 1864) x x xCyphastrea sp. 1 x xEchinopora gemmacea (Lamarck, 1816) xEchinopora hirsutissima Edwards & Haime, 1849 xEchinopora horrida Dana, 1846 xEchinopora lamellosa (Esper, 1795) x x xEchinopora mammiformis (Nemenzo, 1959) x

Family OCULINIDAEGalaxea astreata (Lamarck, 1816) xGalaxea fascicularis (Linnaeus, 1767) x x xAcrhelia horrescens (Dana, 1846) x x

Family MERULINIDAEHydnophora grandis Gardiner, 1904 xHydnophora microconos (Lamarck, 1816) x x xHydnophora pilosa Veron, 1985 xHydnophora rigida (Dana, 1846) xHydnophora exesa (Papas, 1766) x xMerulina ampliata (Ellis & Solander, 1786) x xMerulina scabricula Dana, 1846 xScapophyllia cylindrica (Edwards & Haime, 1848) x x xParaclavarina triangularis (Veron & Pichon, 1980) x

Family MUSSIDAEScolymia vitiensis Bruggemann, 1877 xScolymia australis (Edwards & Haime, 1849) x x xAcanthastrea sp. amakusensis Veron, 1990 x x xAcanthastrea echinata (Dana, 1846) x x xAcanthastrea hillae Wells, 1955 x xLobophyllia corymbosa (Forskål, 1775) x x xLobophyllia costata (Dana, 1846) x x xLobophyllia hataii Yabi, Sugiyama & Eguchi, 1936 x xLobophyllia hemprichii (Ehrenberg, 1834) x x xLobophyllia pachysepta Chevalier, 1975 xSymphyllia agaricia Edwards & Haime, 1849 xSymphyllia radians Edwards & Haime, 1849 xSymphyllia recta (Dana, 1846) xSymphyllia valeniennesii Edwards & Haime x x

Family PECTINIIDAEEchinophyllia aspera (Ellis & Solander, 1786) x x xEchinophyllia echinata (Saville-Kent, 1971) x xEchinophyllia sp. 1 x


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Islands IslandsMycedium elephantotos (Pallas, 1766) x xPectinia alicicornis (Saville-Kent) xPectinia elongata Rehberg, 1892 xPectinia lactuca (Pallas, 1766) xPectinia paeonia (Dana, 1846) x xOxypora lacera (Verrill, 1864) xOxypora glabra Nemenzo, 1959 x

Family CARYOPHYLLIIDAEEuphyllia (E.) glabrescens (Chamisso & Eysenhardt, 1821) x x xEuphyllia cristata Chevalier, 1971 xEuphyllia anacora Veron & Pichon, 1980 xEuphyllia divisa V eron & Pichon, 1980 xPlerogyra simplex Rehberg, 1892 x x xPlerogyra sinuosa (Dana, 1846) xPhysogyra lichtensteini Edwards & Haime, 1851 x

Family DENDROPHYLLIIDAETurbinaria frondens (Dana, 1846) xTurbinaria mesenterina (Lamarck, 1816) xTurbinaria peltata (Esper, 1794) xTurbinaria reniformis Bernard, 1896 x x xTurbinaria stellulata (Lamarck, 1816) x x xTurbinaria sp. 1 x

Order COENOTHECALIAFamily HELIOPORIDAE

Heliopora coerulea (Papas, 1766) x x xOrder STOLONIFERAFamily TUBIPORIDAE

Tubipora musica Linnaeus, 1758 x xOrder MILLEPORINAFamily MILLEPORIDAE

Millepora dichotoma Forskål, 1775 x x xMillepora exaesa Forskål, 1775 xMillepora foveolata Crossland, 1952 x xMillepora intricata Edwards & Haime, 1857 xMillepora latifolia Boschma, 1966 x xMillepora murrayi Quelch, 1884 xMillepora platyphylla Hemprich & Ehrenberg, 1834 x x xMillepora tenera Boschma, 1949 xMillepora tuberosa Boschma, 1966 x x xMillepora sp. 1 x

Total species 385 253 159Total genera 66 56 43

diaserid species dredged from the lower reefslopes (ca. 100 m), and probably occur in Palauif similar habitats were dredged; and one is ahydnophorid species collected from two sta-tions on Guam.

1. General geologic history of the EasternPhilippine Sea

According to current plate tectonic hypothe-

ses the Mariana Fore-arc Ridge was once a partof the Palau-Kyushu Ridge, from where it hasbeen displaced to its present position at theeastern margin of the Philippine Sea by severalepisodes of arc ridge rifting, basin develop-ment, and active arc volcanism. A brief geo-logic history that led to the formation of theEastern Philippine Sea Basin and the migrationof t he Mariana Fore-arc Ridge to its present

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location is given in the following series ofevents that have been summarized from Karig,1975; Hilde et al., 1977; Mrozowski and Hayes,1980; Scott et al., 1980; Meijer et al., 1983;Reagan and Meijer, 1984: 1) Prior to about 45million years (my) ago the Pacific Plate wassubducting beneath the Asian Continent and atransform fault boundary most likely occupiedwhat is now the Palau-Kyushu Ridge, 2) Achange in the direction of motion of the PacificPlate about 43 my ago to a more westerly direc-tion initiated subduction along the trend of thetrans form fault boundary, 3) The Palau-Kyushu Ridge was then formed by arc volca-nism along the trend of the subduction zonebetween 43 and 32 my ago, 4) The Palau-Kyushu Ridge rifted apart about 32 my ago,beginning formation of the Parece-Vela Basinby backarc spreading, and eastward displace-ment of the fore-arc region of the Palau-Kyushu Ridge north of the Palau Islands, 5)About 20 my ago arc volcanism commencedimmediately west of the old eastward riftedPalau-Kyushu fore-arc, forming the WestMariana island arc ridge, 6) Arc volcanism onthe West Mariana island arc ridge continueduntil about 9 to 5 my ago, 7) About 5 my agothe West Mariana arc ridge rifted beginningthe formation of the Mariana Trough by back-arc spreading and diplacement of the WestMariana fore-arc region eastward to eventuallybecome the present fore-arc region of the Mari-ana island arc ridge, and 8) Sometime prior to1.3 my ago, arc volcanism formed the presentlyactive Mariana volcanic island arc ridge imme-diately west of the old eastward rifted westMariana fore-arc.

In searching for explanations for the lowerreef-building coral diversity in the Mariana Is-lands it will be argued here that the geologichistory of the two island groups in relation tothe formation of the Eastern Philippine Sea canmost satisfactorily provide some answers.

2. Time-distance emplacement of the fore-arc stratigraphic units during the forma-tion of the Eastern Philippine Sea

Uplifted sections of Mariana fore-arc islandsof Tinian, Saipan, and particularly on Guam(Cloud et al., 1956; Doan et al., 1960; Tracey et

al., 1964) have preserved the most completeaccessible stratigraphic record of deposits thatspan the historical development of the EasternPhilippine Sea (Karig, 1975; Scott et al., 1980;Meijer et al., 1983; Reagan and Meijer, 1984).

On the southernmost Mariana island ofGuam, volcanic deposits of the Facpi (latemiddle Eocene) and Alutom (late Eocene toearly Oligocene) Formations (as revised byReagan and Meijer, 1984) were laid down priorto rifting when the fore-arc was part of thePalau-Kyushu Ridge system. Intraformationalreefal and nonreefal limestones also occurwithin the Alutom volcanic deposits (Sch-langer, 1964; Reagan and Meijer, 1984; Siegristand Randall, 1992). Presence of reefal lime-stones indicate near sea level conditions for atleast part of the eruptive Alutom deposits.

According to Scott et al. (1980) there is noevidence of arc volcanism preserved in eitherthe island fore-arc or back-arc system duringthe early period of Parece-Vela Basin forma-tion. There is also apparently a hiatus of shal-low water calcareous deposition in the Marianafore-arc during a significant period of timeduring the formation of the Parece-Vela Basinas well. The Miocene eruptive sequence ex-posed on Guam (Umatac Formation) was de-posited after arc volcanism was initiated alongthe West Mariana Ridge. The Maemong Lime-stone deposits that crop out along the south-west mountain slopes and in the Talofofo RiverBasin of southern Guam were previously in-cluded as a member of the Umatac Formationby Tracey et al. (1964). According to Tracey(pers. comm. in Siegrist and Randall, 1992)Maemong Limestone beds along the southwestmountain slopes that crop out on Facpi volcan-ic flows should now be considered youngestOligocene on the basis of recent correlationsbetween Deep Sea Drilling Project results andParis Basin Tertiary sections, and the Mae-mong Limestone deposits which unconform-ably overlies Umatac volcanics in the TalofofoBasin is to be considered lower Miocene. Ap-parently these Maemong Limestone depositsreflect temporal and spacial north-to-south sha-llowing of waters around emerging volcanichighs (Schlanger, 1964; Siegrist and Randall,1992).


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Further shoaling along the fore-arc broughtmore waters into the photic zone, which onGuam produced a number of middle and upperMiocene carbonate units that include theBonya, Alifan, Janum, and Barrigada Lime-stones. Although Tracey et al. (1964) mappedthese limestones as separate time-stratigraphicunits, they may represent, in part, facies modi-fications of each other (Siegrist and Randall,1992). The Mariana Limestone of Pliocene-Pleistocene age is the most extensive carbonateunit on Guam, Rota, Aguijan, and Tinian, butat many sites fossil control evidence of the agehas not been uncovered (Siegrist and Randall,1992). The time-distance implacement of car-bonate units since the opening up of the Mari-ana Trough is somewhat tenuous because ofuncertainties of the exact timing of the Mari-ana fore-arc rifting and age of the late Miocene-Pliocene-Pleistocene limestones. If the time ofrifting is placed at about 5 my ago, the MarianaLimestone, as well as part of the BarrigadaLimestone have been implaced during theopening of the Mariana Trough and the earliercarbonate units during the shoaling of theWest Mariana Ridge. In summary, regardlessof the timing of rifting of the Mariana fore-arc,stratigraphy as represented in the presentMariana fore-arc deposits, supports the hy-pothesis of rather continuous shallow-watercarbonate deposition throughout the Neogeneand continuing to the present time.

3. Effect of the formation of the EasternPhilippine Sea on the biogeography ofcorals of the Mariana Islands

It appears that the development of the East-ern Philippine Sea has had an important effecton the biogeography of reef-building corals inthe Mariana Islands principally because of twohistorical events.

The first of these historical events was theprobable drowning of the Mariana fore-arcbelow the depth for hermatypic corals to liveduring the Oligocene opening of the Parece-Vela Basin. Supporting this view is the ab-sence of Oligocene reefal carbonates in the pre-sent Mariana fore-arc islands. With emergenceor shoaling of the fore-arc to depths favorablefor reef corals during the development of the

West Mariana Ridge the hermatypic coralfauna would have to be reintroduced. Had thefore-arc remained emergent during the forma-tion of the Parece-Vella Basin, it would havemost likely carried with it the early Oligocenereef coral fauna that was extant on the Palau-Kyushu Ridge at the time of rifting. Thetiming of the fore-arc submergence may havebeen crucial, because the appearance of generain the Eocene that are now the most diverseand important reef builders, such as Acropora,Montipora, and Porites, were undergoing signifi-cant speciation at that time. Out of the 141corals from Palau that have not been found inthe present Mariana Islands, about 40 percentof them are Acropora, Montipora, and Poritesspecies.

The second of the historical events that hashad an important effect on the reef-buildingcoral biogeography of the Mariana Islands wasthat during the development of the EasternPhilippine Sea the present day Mariana fore-arc has been displaced hundreds of kilometersnorthward and eastward away from the highcoral diversity Western Pacific biogeographicregion into the mainstream of the westward-flowing North Equatorial Current. Evidencefor such a displacement comes from paleo-magnetic latitude analysis on rocks from DSDPHoles 447A, 448, and 448A sampled at presentday 18°N Lat. on the Palau-Kyushu Ridge thatindicate implacement at 5° to 10° north orsouth of the equator (Scott et al., 1980).

Displacement of the Mariana fore-arc intothe mainstream of the North Equatorial Cur-rent is significant because corals are dispersedalmost exclusively by ocean currents whichhave carried planulae and gametes from theirplace of origin to other geographic regions oftheir range. Jokiel (1990) shows that rafting ofsettled coral planulae on floating objects mayalso be an important dispersal agent as well.Examination of reef-building coral isopangen-eric lines on a map of the Pacific Ocean show ageneral attenuation in an eastward directionfrom the high diversity Western Pacific regionVeron (1986). Currents in the Mariana Islandsare flowing toward the high diversity WesternPacific rather than from it. The eastward-flowing Equatorial Counter Current has most

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likely been an important conduit during theTertiary for dispersal to the Eastern and West-ern Caroline and Marshall Islands. Further-more, the Marshall Islands higher coral diver-sity in comparison that of the Mariana Islandsmay be a result of the Marshall Islands relative-ly geologically recent movement through theEquatorial Counter Current region as a resultof the Pacific Plates northwestern movement.The Marshall Islands, particularly the southernMarshalls, are still being affected by dispersalfrom the west via the Equatorial Counter Cur-rent. Although the Equatorial Counter Currentis a rather narrow conduit for dispersal, satelliteimagery shows that its effective latitudinalrange for dispersal is greatly enhanced by sea-sonal displacement, El Niño phenomenon, andeddies and gyres generated by climatic events.

Since shoaling and emergence of the Mari-ana fore-arc during the development of theWest Mariana Ridge to the present time, themost important agent for dispersal of reef-building corals to the Mariana Ridge appearsto have been the westward-flowing North Equ-atorial Current which transports coral gam-etes, planulae, and rafted propagules from theMarshall Islands. The Mariana Islands reef-building coral fauna appears to be an attenua-tion of the Marshall Islands fauna, as the twoisland groups have a greater percentage of spe-cies in common than do the Mariana and PalauIslands. The present coral fauna of the Mari-ana Islands is for the most part composed ofthose species which are good dispersers, thosewith the most widespread ranges, which iswhat would be expected with the above pro-posed pathway of coral dispersal. As an exam-ple, Richmond (1987) has shown that Pocillo-pora species are very good dispersers, and it isinteresting that there are nearly as many spe-cies of this genus in the Mariana Islands as arein the Palau and Marshall Islands.

Distribution of Reef-Building Corals in theMariana Islands

1. General geographic and geologic settingThe Mariana Islands consists of 15 principal

emergent islands scattered along a mostly sub-mergent ridge axis that lies west of the Mari-ana Trench subduction zone (Figs. 1 and 2). A

number of shallow banks with reef-buildingcorals and deeper submarine prominences lack-ing them also occur along the ridge axis. Theislands can be divided into two distinct geo-logic groups consisting of the six southern isl-ands of Guam, Rota, Aguijan, Tinian, Saipan,and Farallon de Medinella that lie on the oldMariana fore-arc ridge axis; and the nine north-ern islands of Anatahan, Sarigan, Guguan,Alamagan, Pagan, Agrihan, Asuncion, Maug,and Farallon de Pajaros that are offset 25 to 35km west of the southern group along theyoung Mariana active volcanic arc ridge axis.Zealandia Bank, which has two small islets thatare generally awash is located between Sariganand Guguan, and a number of other smallemergent islets are also associated with some ofthe other principal islands. As a group the sixsouthern islands can be characterized as rela-tively old inactive volcanic islands overlain onmuch, or all, of their emergent surfaces bylimestone deposits. In contrast all the ninenorthern islands are geologically young activevolcanic islands and lack significant emergentlimestone deposits. Pagan has a few narrowemergent bands of Holocene limestone, gener-ally less than two meters in elevation, at sever-al locations along the eastern, northern, andwestern shorelines (Siegrist and Randall, 1989).

2. Distribution of coralsThe most conspicuous aspects of reef-

building coral distribution within the MarianaIslands is the lower diversity in the northernisland group and the variation in the numberof species collected within and between islandsof both the northern and southern islandgroups (Tables 1–3). All but one of the 159reef-building coral species, Millepora foveolata,and all 43 genera collected from the NorthernMariana Islands were also collected from theSouthern Mariana Islands. There are 94 spe-cies and 14 genera collected from the SouthernMariana Islands that were not found in theNorthern Mariana Islands.

The significant difference in reef-buildingcoral diversity between the Northern andSouthern Mariana Islands is in part due to thereduced effort (number of collecting stationsand number of specimens collected) and the


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Table 3. The distribution of the number of reef-building coral genera and species collected from thevarious island in the Mariana Islands.

Genera Species

SOUTHERN MARIANA ISLANDSGuam 56 253Rota 38 167Aguijan 34 132Tinian 40 141Saipan 52 206Farallon de Medinella 7 22Total Southern Islands 57 255

NORTHERN MARIANA ISLANDSAnatahan 36 99Sarigan 15 20Guguan 18 43Alamagan 6 6Pagan 38 131Agrihan 32 67Asuncion 12 12Maug 33 66Farallon de Pajaros 5 5Total Northern Islands 43 159

Total of all the Mariana Islands 56 254

smaller percentage of potential coral habitatssampled from in the northern islands (Table 1).At most islands there is a direct correlationbetween the number of collecting stations andspecies diversity (Tables 1 and 3). Regardlessof the reduced collecting and habitat samplingeffort in the northern islands, a number ofother factors could also be important con-straints on diversity there.

Lower species diversity is partly a result ofreduced habitat diversity in the northern isl-ands. Arborescent species of Acropora areabsent on islands in both the northern andsouthern island groups where barrier reef lag-oons or well-protected leeward coasts or emb-ayments are lacking. Even in the well-defineddeepwater crater lagoon at Maug Island, noarborescent Acropora species were found.

Lower coral diversity may be related to theyounger geologic age of the northern islands,but apparently it does not require long periodsof time for newly emergent islands to acquire afairly diverse coral fauna. The northern is-lands developed by arc volcanism sometimeafter the fore-arc rifted away from the WestMariana Ridge and thus have had a signifi-

cantly shorter period of time to aquire theirpresent coral fauna than the southern fore-arcislands. The oldest dated rocks from the vol-canically active northern islands are 1.3 my(Meijer et al., 1983), and thus the present coralfauna of 159 species has presumably been ac-quired since that time.

Frequent disturbance from volcanic erup-tions and typhoons may keep coral diversitylow by keeping the communities in an earlystage of successional development in the north-ern islands. There is no disturbance from vol-canic eruptions in the southern islands, andtyphoon effects are more severe on the pre-dominantly smaller northern islands wherethere is no significant protected habitats to actas refugia. Less frequent disturbance in thesouthern islands may even tend to enhancecoral diversity according the model of succes-sional regulation by intensity and frequency ofdisturbance proposed by Connell (1978).

Higher latitudes of the North Equatorial Cur-rent that sweeps by the northern islands maybe less effective as a dispersal agent because offewer islands to the east as a source of planu-lae.

Literature Cited

Chase, T. E., H. W. Menard and J. Mammerickx. 1971.Topography of the north Pacific. University of Cal-ifornia, San Diego Institute of Marine Resourses.Tech. Rept. 17.

Cloud, P. E., Jr., R. G. Schmidt and H. W. Burke. 1956.Geology of Saipan, Mariana Islands; Part 1, GeneralGeology. U.S. Geol. Sur. Prof. Pap. 280A, 126 pp.,pls. & maps.

Connell, J. 1978. Diversity in tropical rain forestsand coral reefs. Science 199: 1302–1310.

Doan, D. B. 1960. Military Geology of Tinian, Mari-ana Islands. U.S. Army, Chief Eng., Intell. Div.,Headq., U.S. Army far East, Tokyo. 149 pp., pls. &maps.

Hess, H. H. 1948. Major structural features of thewestern North Pacific, an interpretation of H.O.5485, bathymetric chart, Korea to New Guinea.Geol. Soc. Amer. Bull. 59: 417–466.

Hilde, T. W. C., S. Uyeda and L. Kroenke. 1977. Evo-lution of the western Pacific and its margin. Tecto-nophysics 38: 145–165.

Jokiel, P. L. 1990. Long-distance dispersal by rafting:

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reemergence of an old hypothesis. Endeavour 14(2): 66–73.

Karig, D. E. 1975. Basin Genesis in the PhilippineSea. In D. E. Karig (ed.), Initial Reports of theDeep Sea Drilling Project. U.S. Govt. Print. Off.,Washing- ton D.C. pp. 857–879.

Meijer, A., M. Reagan, M. Shafiqullah, J. Sutter, P.Damon and S. Kling. 1983. Chronology of volcanicevents in the eastern Philippine Sea. Amer.Geophy. Union Mongr. 27: 349–359.

Mrozowski, C. L. and D. E. Hayes. 1980. The evolu-tion of the Parece Vela Basin, eastern PhilippineSea. Earth and Planetary Sci. Lett. 46: 49–67.

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Reagan, M. K. and A. Meijer. 1984. Geology andgeochemistry of early arc-volcanic rocks fromGuam. Geol. Soc. of Amer. Bull. 95: 701–713.

Randall, R. H. and R. F. Myers. 1983. Guide to theCoastal Resources of Guam: Vol. 2, TheCorals. Univ. of Guam Press, 129 pp.

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Siegrist, H. G., Jr., and R. H. Randall. 1989. Samplingimplications of stable isotope variation in Holo-cene corals from the Mariana Islands. Micronesica22(2): 173–189.

Siegrist, H. G. Jr. and R. H. Randall. 1992. CarbonateGeology of Guam: Summary & Field Guide. Univ.of Guam, Water & Energy Research Institute of theWestern Pacific and Marine Laboratory, 39 pp. &pl.

Schlanger, S. O. 1964. Petrology of the Limestones ofGuam. U.S. Geol. Sur. Prof. Pap., 403D, 52 pp. & pls.

Tracey, J. I., Jr., S. O. Schlanger, J. T. Stark, D. B. Doanand H. G. May. 1964. General Geology of Guam.U. S. Geol. Sur. Prof. Pap., 403A, 104 pp., pl. &maps.

Veron, J. E. N. 1986. Corals of Australia and theIndo-Pacific. Angus & Robertson, Australia, 644pp.

Veron, J. E. N. 1992. Hermatypic Corals of Japan.Australian Inst. Mar. Sci., Monog. Ser. Vol. 9, 234pp.

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(Accepted on 10 January 1994)

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