The Extinction of Partula on Moorea1

The Extinction of Partula on Moorea 1

JAMES MURRAy,2 ELIZABETH MURRAY,z M ICHAEL S. JOHNSON,3 AND BRYAN CLARKE4

A BST RACT: Land snails of the genus Partula from the isla nd of M oorea in French Pol ynesia have for more than a century pro vided a natural laboratory for the study of variation, genet ic polymorphism, and speciation. As a resul t of the inte ntional introduction of the predatory snail Euglandina rosea, all the species of Partula from Moorea are now extinct in the wild. Sin: e Euglandin.a is spreading rapidly on Tahiti, the demise of Partula on. tha t I sI ~nd also IS imminent. Attempts are being made through the In ternation al Umon fo ~ t~e Conservation of Nature for the captive breeding of those stocks tha t rem ain III the laboratory.

OWING TO THEIR unusual diversity, land snails FIELD WORK, 1987 of the gen us Partula inhabitin g the island of Moorea in French Polynesia have excited the Recognizing that a number of species of interest of students of variation and evo lution Partula were in grave danger ofextinction, the for more than a century (Crampton 1932, Ca ptive Breeding Specialist G ro up of the In Garrett 1884, Johnson et al. 1986, Murray ternational Union for the Conservation of and Clarke 1980). In an earlier paper (Clarke Nature (IUCN) arranged a meeting in Lon et al. 1984), we reported a threat ofimminent don during April 1987 to consider steps for extinction of these animals following the their rescue . The working party recommended, introduction of the predatory snai l Euglandina among other things, an immediate attempt to rosea. This note simply documents the final collect any remaining Moorean species to sup stage of that unfort unate chain ofevents. plement the stocks already held in captivity. The tragedy was set in motion in 1967 by Supported by the IUCN, two ofus (J. M urray the introduction of Achatinafulica, the giant and E.M urray) spent 3 weeks in June and July African snail, into Tahiti for food. It quickly 1987 in F rench Polynesia surveying the current spread to the other islands of the Society situa tio n and co llecti ng the species that could gro up and became a serious agricult ural pest. still be found . The subsequent introduction of Euglandina On the basis ofan extensive survey of Moo was a misguided attempt to control the enor rea we believe that the Partula of that island mous populations of Achatina, despite the are'extinct in the wild . We visited 16 valleys on lack ofevide nce th at Euglandina has ever been the island, paying particular attention to two effective in doing so (M ead 1979). T he impact po ssibilities for locating relict p opul~ t i on s . of Euglandina on Partula, however, has been Fi rst, populations mig ht be presen t high up disastro us (Clarke et al. 1984, Pointier and in the heads of the valleys. We climbed to the Blanc 1984). ridge crest in four valleys, Paparo a, Faama ariri, U ufau, and Maramu, and searched without success (Figure I). We know that Partula formerly occupied at least three of 1 Manuscrip i accepted 7 No vembe r 1987. these crests , and probably all four. Moreover, 2 Department ofBiology, University of Virginia, Ch ar Euglandina was found at or near the top in lotlesvillc, Virginia 22901. every case.Second, populations might be cut 3 Department of Zoology,University of Weslern Au s tralia, Nedlands, Weslem Australia 6009. off and protected by minor geographical or 4 Department of Genetics, University of No ttingham, ecological barriers. We visited three valleys Nottingham NG7 2UH, England . that might provide such isolation, Tehaoa and 150 FI GURE I. A map of Moorea showing field work undertaken in 1987. Solid lines mark the mountain ridges. Dashed lines indicate routes followed in searching for Partula. 152 PACIFIC SCIENCE, Volume 42, July/October 1988

Taapurau in the northwest and Oio in the On Tahiti, Partula stillexist, but the situation south. In each valley we found living Eu is deteriorating rapidly. In 1984, the area in glandina but no Partula. While we cannot, of vaded by Euglandina extended from Taravao course, be absolutely sure that there are no to Papara on the south coast (Figure 2). Our surviving populations of Partula, we believe samples from 1987 show that, unless there has the probability is very small. We conclude been some leapfrogging, the infested area now that P. sutura/is (including P. dendroica), P. extend s all the way to Pirae in the northwest. taeniata, P. tohiveana (including P. olympia), We have positive evidence for the persistence P. mooreana, P. aurantia, P. mirabi/is, and P. of Partula in only two valleys, Tiarei (Hono ex igua all should be considered extinct in the fea) and Mahaena. The remaining popula wild; and P. exigua, ofwhich no living animals tion s represent P. otaheitana rubescens, P. survive in captivity, is considered completely affinis, P. hya/ina , and P. clara. extinct. The last wild Partula on Moorea were On Huahine, Euglandina has not yet been seen in Haapiti Valley during November 1986 introduced, and Partula species continue to (by B. Clarke), and samples were collected for flourish . We have confirmed that P. varia and captive breeding. P. rosea are still represented by substantial

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FIGURE 2. A map of Tah iti. Solid lines mark the mountain ridges. Cro ss hatching indicates the area known to be infested with Euglandina rosea in 1984. By 1987, Partula had disap peared from the valleys of Pirae, Papehue, and Tereehia, but could still be found in Tiarei and Mahaena. Extinction of Partuta-MURRAY ET AL. 153 populations, despite the fact that these two in an unusually simple predator-prey system, species are exploited for the trade in shell or through cannibalism. jewelry. The economic importance of these species might provide a basis for a campaign against the importation of Euglandina. There ACKNOWLEDGMENTS is no reason to believe that P. arguta, a rare We thank the members of the Centre de montane species, is in danger. The introduc I'Environnement, fIe de Moorea, especially tion of Euglandina to any of the other islands Rene Galzin and Joel Andre, for their interest should be rigorously discouraged. in our work and their offer ofsupport. We are indebted to Werner Loher and to Rick and Bonnie Steger for their hospitality at the CONSERVATION EFFORTS Gump Biological Station of the University of California (Berkeley) on Moorea. Finally, we Despite the loss of the wild populations of appreciate more than we can say the financial Moorean Partula, the situation is not hopeless. support of the Captive Breeding Specialist In the laboratories of our three home insti Group of the International Union for the tutions, representatives of all the Moorean Conservation of Nature, and particularly species except P. exigua are still living. Under Ulysses Seal, who made the whole venture the auspices ofthe Captive Breeding Specialist possible. We hope that the survival of at least Group, efforts are being made to organize a some species of Partula will be their reward. captive breeding program at a number ofzoos in the United States and Europe. The first breeding units have been established at the LITERATURE CITED Jersey Wildlife Preservation Trust and at the London and Berlin zoos. Several institutions CLARKE, B., J. MURRAY, and M. S. JOHNSON. have expressed interest in cooperating in the 1984. The extinction ofendemicspecies by a captive breeding program. program ofbiological control. Pac, Sci. 38: We are also exploring the possibility of 97-104. establishing enclosed wild populations of CRAMPTON, H . E. 1932. Studies on the varia Partula on Moorea. Two biological stations tion, distribution, and evolution of the on the island, the Centre de l'Environnement, genus Partula. The species inhabiting Moo fIe de Moorea (Antenne de Museum National rea. Carnegie Inst. Wash. Pub. 410: 1-335. d'Histoire Naturelle) and the Gump Biolog GARRETT, A. 1884. The terrestrial mollusca ical Station of the University of California inhabiting the Society Islands. J. Acad. (Berkeley), may be able to help with the estab Nat. Sci. Phila. (Ser. 2) 9: 17-114. lishment and monitoring ofexclosures (fenced JOHNSON, M . S., J. MURRAY, and B. CLARKE. areas from which the carnivores have been 1986. Allozymic similarities among species removed). ofPartula on Moorea. Heredity 6:319-327. Our initial hope that the wave ofextinction MEAD, A. R. 1979. Economic malacology created by Euglandina would be followed with particular reference to Achatinafulica. shortly by the disappearance of the predator Pages I-ISO in V. Fretter and J. Peake, eds. has not yet been realized. We do not know The pulmonates. Vol. 2B. Academic Press, how the sparse residual populations of Eu New York. glandina are maintaining themselves. Although MURRAY, J., and B. CLARKE. 1980. The genus the carnivore can eat Achatina, the African Partula on Moorea: Speciation in progress. snails are now very scarce on Moorea. Eu Proc. R. Soc. London Ser. B. 211 : 83-117. glandina can still be found even in those areas POINTIER, J. P., and C. BLANC. 1984. Achatina that have been longest devoid of Partula. The fulica en Polynesie Francaise, Report ofthe extermination of Euglandina by artificial con Museum National d'Histoire Naturelle, trol measures does not seem to be practicable, Ecole Pratique des Hautes Etudes, Antenne and we can only continue to hope for its nat de Tahiti, Centre de I'Environnement, lie ural elimination through unstable oscillations de Moorea.