Extant Populations of Endemic Partulids on Tahiti, French Polynesia
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Oryx Voi 33 N:- i Juy 139;) Extant populations of endemic partulids on Tahiti, French Polynesia Trevor Coote, Eric Loeve, Jean-Yves Meyer and Dave Clarke Abstract The current distribution of endemic partulid fieldwork undertaken between 1995 and 1997. Native snails on Tahiti in French Polynesia reflects the danger snails still exist in good numbers in two areas, at of ignoring expert advice and introducing an alien opposite ends of the island. In other areas, sightings of species into a fragile island ecosystem. The endemic single or a few individuals indicate remnant popu- tree-snail fauna of the island now faces extinction. lations now on the edge of extinction. Efforts to protect Although the extinction of the native species of Partula these populations and others in French Polynesia are (Partulidae; Polynesian tree snails) on Moorea in French being planned in collaboration with local government Polynesia is well known in the world of conservation authorities. biology, losses on other Pacific islands are less well described. This paper presents an update on the status Keywords Biological control, conservation, Euglandina, of partulid snail populations on Tahiti in the light of Partula, Tahiti. The situation in Tahiti has been less well docu- Introduction and background mented. Tahiti is the largest (1045 sq km) and the When the giant African land snail Achatina fulica was highest (2241 m) island of the Society Island introduced into French Polynesia as a food source in archipelago. It comprises Tahiti-Nui (large island) and 1967, it escaped and bred so rapidly that it threatened Tahiti-Iti (small island) joined by an isthmus at Taravao the economy of the islands, destroying food crops and (Fig. 1). Between 1975 and 1978 E. rosea was introduced local garden flora (Pointier & Blanc, 1985). The solution into Tahiti at three localities: the Botanic Garden at to the problem at that time was perceived by the local Papeari (now the Jardin Botanique Harrison Smith); the government authorities to be the introduction of a Station de Recherche Agronomique at Papara; and on carnivorous snail, Euglandina rosea, a native of Florida, government (Service de l'Economie Rurale) land on the USA. Despite warnings from authorities on molluscan plateau at Taravao. biology (J. B. Burch, pers. comm.), the introductions The taxonomy of Tahitian partulids was first de- took place on Tahiti in 1975 and on Moorea in 1977. scribed in detail by Hartman (1881), Garrett (1884) and The extinction of the seven endemic Moorean species Mayer (1902). Drawing on these studies, together with of Partula tree snails, attributable to this introduction, his extensive fieldwork, Crampton (1916) identified is well documented (Clarke et al., 1984; Murray eight species of the genus Partula on Tahiti. In addition, et al, 1988; Gould, 1991; Cowie, 1992), largely because he described a number of varieties of each, as well as of the extensive scientific research on the partulids eight subspecies of P. otaheitana. This taxonomy has of that island by evolutionary biologists (see especially subsequently been revised, most significantly by Kondo Crampton, 1932; Johnson et al, 1993). (1968), who, in addition, recognized one species of Samoana. Since then, there have been minor revisions to the taxonomy of both genera. Trevor Coote (corresponding author) Institute of Zoology, Zoological The partulid fauna of Tahiti have not been studied in Society of London, Regents Park, London NW1 4RY, UK. as much detail as that of Moorea in recent years. Fax: + 44 171 586 2870; e-mail: [email protected] Consequently, less notice was taken of the extinctions Dave Clarke Invertebrate Conservation Unit, Zoological on Tahiti. In 1984, it was known that the area invaded Society of London, Regents Park, London NW1 4RY, UK. by E. rosea extended from Papara on the south coast to Fax: +44 171 722 5390; e-mail: [email protected] Taravao (Murray et al., 1988). Eric Loeve BP 3577 Papeete, Tahiti, French Polynesia. Tel/Fax: + 689 42 65 61; e-mail: [email protected] Jean-Yves Meyer Delegation a la Recherche, BP 20981 Papeete, Surveys Tahiti, French Polynesia. Fax: + 689 43 34 00; e-mail: [email protected] The situation on Moorea and Tahiti is part of a much wider problem for this family of snails because E. rosea Received 2 February 1998. Accepted 2 December 1998 has been introduced into many of the islands of the 1999 FFI, Oryx, 33(3), 215-222 215 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 30 Sep 2021 at 03:09:35, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.1999.00065.x 216 T. Coote ef al. Pacific basin where partulids occur. The Partula Prop- hue and Tereehia (Murray et al, 1988). Since 1994 agation Group was established in 1986 in response to PILSG has conducted surveys in a number of valleys this threatened extinction to co-ordinate the captive on Tahiti, as well as on six islands of the Marquesas breeding of snails held in captivity at that time. To archipelago. reflect the broader interests and activities of the By 1994, extrapolating from the situation on group, it was renamed the Pacific Island Land Snail Moorea, it was assumed that all tree-snail species Group (PILSG) in 1994, as part of the IUCN Mollusc in Tahiti were extinct in the wild, and that only Specialist Group, and aims to conserve the family P. otaheitana, P. hyalina and P. nodosa remained ex- Partulidae, as well as other endemic snail families of tant in captive-breeding programmes (Pearce-Kelly the Pacific region, notably Achatinellidae (Pearce- et al, 1994). Samples taken by B. Clarke and J. Kelly et al, 1994). In 1987, a survey by J. J. and E. J. Murray show that there were flourishing pop- Murray, supported by the Captive Breeding Specialist ulations on Tahiti before the introduction of E. Group of the IUCN, reported only four taxa remain- rosea and a decline soon after (J. J. Murray, pers. ing (P. otaheitana rubescens, P. affinis, P. hyalina and P. comm.). However, later that year, P. Pearce-Kelly clam), with positive evidence of their existence only (Zoological Society of London and PILSG) found a in Tiarei and Mahaena Valleys in the north-east. Par- remnant population of P. otaheitana at 1400 m, close to tula had disappeared from the valleys of Pirae, Pape- the TV antenna by the crest of Mt Marau (Plate 1), in Mahina Papenoo Papeete Tiarei 24 20 Mahaena Faa'a 22 Hitiaa TAHITI-NIJI Punaauia TAIARAPU (TAHITI-ITI) N Fig. 1 Extant populations of partulids discovered on Tahiti since 1994 (includes administrative districts): 1, Taharaa crest (Mahina); 2, Mt Marau (Faa'a); 3, Punaruu Valley (Punaauia); 4, Taharuu (Teihomono crest and above) (Papara); 5, Tuauru Valley (Mahina); 6, Tahaute Valley (Mahaena); 7, Mt Mauru (Hitiaa); 8, Papeno'o caldera (Papeno'o); 9, Viriviriterai Plateau (Faaone); Te Pad area: 10, Fareara Point; 11, Faaroa Valley; 12, Baie de Taapeha; 13, Baie de Piarere; 14, Vaitehipa Valley. Introduction points: 15, Papeari; 16, Papara; 17, Taravao Plateau. Main peaks: 18, Mt Aorai; 19, Mt Orohena. Other: 20, Tiarei; 21, Papehue Valley; 22, Mahaena; 23, Pirae; 24, Papeete; 25, Tereehia Valley (E. Loeve). 1999 FFI, Oryx, 33(3), 215-222 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 30 Sep 2021 at 03:09:35, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.1999.00065.x Extant populations of endemic partulids on Tahiti 217 it was only a matter of time before E. rosea eliminated any surviving populations. The surveys of 1995, as recommended in the 1994 Action Plan (Pearce-Kelly et ah, 1994), were therefore primarily seen as a rescue mission, with snails being collected for an expanded captive-breeding programme in Europe and, particu- larly, in the USA, where most of the collection went. Subsequent partulid finds in other localities have been discoveries, often incidental to other work, rather than organized surveys (see Table 1). Methods and results ..^l^tCr*"" The fieldwork action plan for 1995 included a list of seven valleys that seemed the most promising sites for finding remaining populations of each of the 10 Plate 1 Partula otaheitana on decaying banana leaf, Mt Marau Tahitian partulid taxa identified (Plate 2). Those loca- (D. Clarke). tions selected were accessible by road or track, and were areas where reserves might be constructed in the the presence of live E. rosea (Pearce-Kelly et ah, 1995), event of finding surviving populations. However, on confirming an earlier sighting earlier that year (B. arrival in French Polynesia, PILSG received further Clarke, pers. comm.). information from E.L. who, until then, was unknown to In 1995, thriving populations of partulids were un- the group. The priority aims were consequently covered in Faaroa Valley, in south-east Tahiti-Iti, and changed, and areas then known to contain populations some individuals in Tahaute Valley, below Mt Mauru of Partula were targeted for survey and collection. on Tahiti-Nui. These unexpected discoveries suggested A data sheet was prepared, based on that drawn up the possibility of other extant populations, and ad- by B. Clarke and J. Murray for their original collections, ditional surveys on Tahiti were included in the and used in the 1991 survey of the Society Islands. This itinerary of the 1995 expedition to the Society and sheet provided a standard format for entering data, not Marquesas Islands (Pearce-Kelly et ah, 1994). only of the number and description of any snails col- Spreading at an estimated rate of 1.2 km/year, E.