An Estimate of the Potential Evolutionary Increase in Species Density in the Polynesian Ant Fauna Author(s): Edward O. Wilson and Robert W. Taylor Reviewed work(s): Source: Evolution, Vol. 21, No. 1 (Mar., 1967), pp. 1-10 Published by: Society for the Study of Evolution Stable URL: http://www.jstor.org/stable/2406735 . Accessed: 18/12/2012 14:10 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Society for the Study of Evolution is collaborating with JSTOR to digitize, preserve and extend access to Evolution. http://www.jstor.org This content downloaded on Tue, 18 Dec 2012 14:10:24 PM All use subject to JSTOR Terms and Conditions EVOLUTION INTERNATIONAL JOURNAL OF ORGANIC EVOLUTION PUBLISHED BY THE SOCIETY FOR THE STUDY OF EVOLUTION Vol. 21 March, 1967 No. 1 AN ESTIMATE OF THE POTENTIAL EVOLUTIONARY INCREASE IN SPECIES DENSITY IN THE POLYNESIAN ANT FAUNA' EDWARD 0. WILSON AND ROBERT W. TAYLOR2 Biological Laboratories,Harvard University,Cambridge, Massachusetts Received September20, 1965 An exceptionallyhigh proportion of the to recognizethat the Polynesianants offer ant speciesof Polynesiaare "tramps,"that an unusual researchopportunity; namely is,species carried about the world by human thechance to comparethe synthetic, poorly commerce.A trulynative fauna is present coadapted faunulae of the eastern and as well on theislands of westernPolynesia. northernarchipelagoes with the older,na- In the easternand northernarchipelagoes, tive,and bettercoadapted faunulae of the however,there may be in fact no truly westernarchipelagoes. A detailedaccount nativespecies at all, the faunulaehere con- of the taxonomyand distributionof indi- sistingof syntheticaggregations of tramp vidual species is being given elsewhere species. Some of these species originated (Wilsonand Taylor, 1967). In thepresent ultimatelyin theIndo-Australian area, some articlewe will describecertain particular in Africa,and some in the New World phenomenawhich might be of generalin- tropics.Most have been carried accidentally terest. to the Pacific islands on European ships, certainlywithin the last 400 years and RELATIONSHIPS OF THE POLYNESIAN probablyno earlierthan the time of Cook's FAUNA firstvoyage (1768-1771). This tramp Our surveyhas includedall of theislands fauna,despite its heterogeneityand youth, fromthe Ellice group,Rotuma, Samoa, and has achievedan orderlinessof sorts.In par- Tonga,eastward to and includingthe Mar- ticular,the numberof specieson an island quesas and Easter Island, and north to is wellcorrelated with the island's area, and Hawaii. New Zealand was excludedfrom somerelated species have acquiredcomple- thecurrent analysis, since it is faunistically mentary(mosaic) inter-and intra-island verydistinct, most or all of its distributionsthat can be explainedeasily fewnative only as the outcome of competitiveex- species having been drawn directlyfrom clusion. In the course of currentstudies Australia (Brown, 1958). The Wallis on theIndo-Australian fauna we have come Islands and Futuna have been intensively collectedonly recently 1 by Mr. GeorgeHunt, Based on researchsupported by U. S. National and theirant faunulaewill be the subject Science Foundation grant no. GB1634. 2 Present address: Entomology Division, of a later separate reportby Hunt and C.S.I.R.O., Canberra, A.C.T., Australia. Wilson. EVOLUTION 21: 1-10. March, 1967 1 This content downloaded on Tue, 18 Dec 2012 14:10:24 PM All use subject to JSTOR Terms and Conditions 2 EDWARD 0. WILSON AND ROBERT W. TAYLOR TABLE 1. A classificationof the Polynesian ant of Hygieneand TropicalMedicine Expedi- speciesaccording to origin. tion were studiedby Santschi (1928). In theperiod 1938-1962, five other entomolo- 1. Endemic to one or more Polynesian archipela- gists, 0. H. Swezey, E. C. Zimmerman, goes: Ectomomyrmex insulanus, Ponera loi, P. T. E. Woodward,G. Ettershank,and R. W. woodwardi, Strumigenys mailei, Pheidole Taylor,made additional collections. A five- aana, P. atua, Vollenhoviapacifica, V. samo- week tourby Taylor and his wifein 1962 ensis,Rogeria exsulans,Adelomyrmex samo- was devotedwholly to collectionand study anus, Camponotus navigator,C. rotumanus, C. flavolimbatus,C. conicus, C. nigrifrons, of the Samoan ants. Polyrhachisrotumana. Classificationof the 83 known Poly- 2. Continuouslydistributed from Indo-Australian nesian species accordingto biogeographic area into Polynesia: originis givenin Table 1, and thecomposi- Prionopelta kraepilini,Platythyrea parallela, tion of the faunulaeof the betterknown Ponera incerta,P. tenuis,Hypoponera con- finis,H. punctatissima,Cryptopone testacea, islands is given in Figures 1 and 2. Two Odontomnachussimillimus, Anochetus graeffei, conclusionsof immediaterelevance can be Eurhopalothrixprocera, Smithistruma dubia, drawnon the basis of thesepartitions, and Strumigenys szalayi, Pheidole fervens, P. on some additionalconsiderations of par- oceanica, P. umbonata, P. sexspinosa,Sole- ticularspecies presented elsewhere by Wil- nopsispapuana, Oligomyrmexatomus, Mono- morium talpa, Tetramoriumpacificum, T. son and Taylor (1967). tonganum, Rogeria sublevinodis,Iridomyr- First, it is apparent that, prior to the mex anceps, Tapinoma minutum, Techno- comingof man, few if any native species myrinexalbipes, Paratrechina minutula, Cam- rangedeast of Rotuma,Samoa, and Tonga. ponotus chloroticus. 3. "Tramp species": certainlydistributed by re- The evidenceis as follows: cent human commerce: to occur in Hypoponera opaciceps, H. zwaluwenburgi, No certain endemics are known Five which Trachymesopus stigma, Leptogenys maxil- Polynesia beyond theseislands. species to be peculiar to the losa, Syscia typhla, Trichoscapa membrani- prior to 1950 were considered of Pacific Ponera fera, Strumigenysgodeffroyi, S. lewisi, S. peripheral areas the [namely Syscia typhla Roger (=Cera- rogeri,Quadristruma emmae, Pheidole mega- swezeyi (Wheeler), pachys silvestriiWheeler), Quadristruma emmae cephala, Solenopsis geminata, Monomorium (Emery) (= Epitritus wheeleri Donisthorpe), destructor,M. latinode,M. floricola,M. fos- Chelaner antarcticm (White) (= Monomorium sulatum,M. minutum,M. pharaonis,Trigly- rapaense Wheeler), and Plagiolepis alluaudi Forel phothrixstriatidens, Tetramorium caespitum, (= P. mactavishi Wheeler = P. augusti Emery)] T. guineense,T. simillimum,Cardiocondyla are now known to occur elsewhere. Three others, emeryi,C. nuda, C. wroughtoni,Iridomyr- Amblyoponezwaluwenburgi (Williams) of Hawaii, mex humilis, Tapinoma melanocephalum, Smithistrumamumf ordi (Wheeler) of the Mar- Anoplolepislongipes, Plagiolepis alluaudi, P. quesas Islands, and Oligomyrmex tahitiensis exigua, Paratrechinabourbonica, P. vaga, P. Wheeler of Tahiti, are still unknown elsewhere longicornis,Brachymyrmex obscurior, Cam- but belong to poorly collected and taxonomically ponotus variegatus. little-knowngenera. Moreover, 0. tahitiensisis 4. "Tramp species" interceptedin quarantine at known solely from the sexual castes and cannot Honolulu but not yet establishedin Polynesia: even be compared with most of the other Indo- Brachyponerasolitaria, Tetramorium caespi- Australianmembers of the genus,which are known tum,Wasmannia auropunctata. only from the worker caste. Thus, the status of 5. Uncertainstatus: these threeremaining "endemics" is very dubious. Amblyoponezwaluwenburgi, Ponera swezeyi, Also, despitea plethoraof subspecificand varietal Smithistrumamumfordi, Oligomyrmex tahi- names applied in the literatureto populations of tiensis,Chelaner antarcticum. species now living in the central and eastern Pacific, we have detected only a single example of true geographicvariation in these populations. The Polynesianant fauna is now rela- The case is furthermorea rather trivial one in- tivelywell known. Samoa, the archipelago volving color and the thickness of propodeal of principalinterest to us, has been espe- spines in samples of Pheidole sexspinosa Mayr from the Marquesas and Society islands. cially well surveyed. Large collections About 20 Indo-Australianant species range to made in the 1920's by the London School some point east or north of Rotuma, Samoa, and This content downloaded on Tue, 18 Dec 2012 14:10:24 PM All use subject to JSTOR Terms and Conditions SPECIES DENSITY IN THE POLYNESIAN ANT FAUNA 3 60- 2A 50 - PO LYNESIA: V) ALL ANT SPECIES Ui U 40 XL A C.,..) A3 *32 U- 0 30 co 2 20 Z 2 29 31 *38 01201 22 2 21 33 10 27 15 5 27 .2 251 I 2 3 25 6 343 28 b26 17.8 .7 .3 18 39 19 0.1 I 10 100 1000 10,000 AREA IN SQUARE MILES FIG. 1. Total number of ant species plottedagainst island area for each of the better collected Polynesia islands. Note the high values for the three large Samoan islands (1-3), this is due to the presence of a substantial native fauna in addition to the tramp species. SAMOA: (1) Savai'i, (2) Upolu, (3) Tutuila. TOKELAU: (4) Fakaofo. DANGER ISLANDS: (5) Motu Kotawa. SOCIETY ISLANDS: (6) Bora Bora, (7) Mehetia, (8) Huahine, (9) Moorea, (10) Raiatea, (11) Tahiti. AUSTRAL ISLANDS: (12) Rimatara, (13) Raivavae, (14) Maria Island, Northeastislet, (15) Rapa. GAMBIER ISLANDS: (16) Mangareva. MARQUESAS: (17) Eiao, (18) Hatutu, (19) Ua Pu,