Bulletin 110 FINAL EDIT.Indd
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Recent data on the distribution of lizards and snakes of the Seychelles SARA ROCHA1,2,3,5, D. JAMES HARRIS1,2, ANA PERERA1, ANDREIA SIlvA1,2, RAQUEL VASCONCELOS1,2,4 and MIGUEL A. CARRETERO1 1 Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal. 2 Departamento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, Praça Gomes Teixeira, 4099-002, Portugal. 3 Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, Vigo 36310, Spain. 4 Departament Biología Animal, Facultat Biología, Universitat de Barcelona, Av. Diagonal, 645, 08028 Barcelona, Spain. 5 Corresponding author: [email protected] HE Seychelles comprise 155 islands scattered unique endemic species (Stoddart, 1971; Geyth Tacross the western Indian Ocean at 4-11º et al., 1979; Braithwaite, 1984a; Montaggioni & S and 45-56º E. Traditionally divided into two Hoang, 1988; reviewed in Gardner, 1986). main groups, the northern, granitic islands and The low coralline islands (Bird, Denis, Coëtivity the southern, coralline islands, they can in fact be and Platte, the Amirantes and the Farquhar groups) differentiated into three geological categories: the were formed very recently, probably less than inner (granitic islands), the low coralline islands 6,000 years ago, from marine sediments sometimes and the raised coralline islands (Baker, 1963; cemented by deposits of guano. Almost all are less Braithwaite, 1984a) (Fig. 1). than 3 m above sea level (Braithwaite, 1984b). The granitic islands consist of a group of about All of the Aldabra group (Aldabra, Cosmoledo 40, clustered together on an undersea shelf of and Astove atolls and Assumption island) are raised granite, the Seychelles bank, and are remnants of coralline islands. Like the low coralline islands, they the Seychelles microcontinent which was isolated are oceanic in origin, formed by reef-building corals following Gondwana breakup, roughly 65 million acting on submerged volcanic seamounts that may years ago (Plummer & Bell, 1995). These comprise have formed some 20 million years ago (Plummer, the islands of North, Silhouette, Fregate, Mahé, 1995) and have thus been submerged and emerged Praslin, La Digue, Curieuse and several smaller several times since their formation. Aldabra's last islands encircling these (Fig. 1). The islands are full submergence dates back to 125,000 years ago generally high, some very mountainous, reaching (Thomson & Walton, 1972). Remaining islands in 914 m above sea level (Morne Seychellois, Mahé). the group, lower than Aldabra itself, were probably Such height results in great habitat diversity and submerged during the last interglacial when sea rainfall. In periods of low sea levels during the level was 10 m higher than present, re-emerging Pleistocene and Pre-Pleistocene ice ages (Colonna slightly later than Aldabra (Taylor et. al., 1979). In et al., 1996; Rohling et al., 1998; Siddall et al., general the coralline islands have limited habitat 2003; Camoin et al., 2004; Miller et al., 2005) most variation and correspondingly lower species of the Seychelles Bank would have been exposed diversity. Aldabra is an exception, possibly due as a single large island, but even when global sea to its slightly older age and proximity to both level was at its highest, most of the granitic islands continental Africa and Madagascar. As currently remained above sea level, allowing the survival of recognized, the native reptiles of the Seychelles 20 Number 110 - Herpetological Bulletin [2009] Herpetofaunal distribution, Seychelles Figure 1. General map of the study area and the principal island groups sampled in this study. Herpetological Bulletin [2009] - Number 110 21 Herpetofaunal distribution, Seychelles comprise around 30 species, 70% of which are sister-taxa, having originated within the Seychelles. endemic (Gerlach, 2007). Systematic studies on However, P. abbotti from Aldabra and Assumption vertebrate fauna at the Seychelles dates back from are closely related to other P. abbotti subspecies the late 1880s, but despite this and even after two from Northwestern Madagascar, resulting from very recent publications covering species accounts an independent colonisation of the southern atolls and tentative distributions (Bowler, 2006; Gerlach, (Rocha et al., 2009a). Ongoing molecular work 2007), precise distribution records are still lacking should clarify the structure within these species. and many distributions are incomplete. Here we report data obtained during roughly 12 weeks of Phelsuma sundbergi sundbergi (Fig. 2) fieldwork between 2005 and 2008 that together, Localities: Grand Soeur 90; Poivre 14; Praslin 99, with the surveys undertaken as part of the Indian 102, 110; Curieuse 81; La Digue 93, 94B, 95, 96. Ocean Biodiversity Assessment 2000-2005, and Easily distinguished from its conspecific by being previous records, provide the most up-to-date the largest species and predominantly green, with distribution record of the lizards and snakes in the small, widespread, red freckles. It is abundant and Seychelles. A total of 121 localities were sampled widespread across its distribution. The individuals (Fig. 1 and Table 1 [Appendix]), covering a wide from La Digue (and Felicite, Cocos, Grand Soeur, range of the coralline and granitic islands, resulting Petite Soeur and Mariane) are often refered to as in approximately 900 observations. Specimens Phelsuma sundbergi ladiguensis. As they are not observed were located with GPS and identified to different from P. sundbergi sundbergi individuals species level following the most recent taxonomic in the field (except for the geographic criteria), revisions in each case. Biogeographic and we do not consider it as a different subspecies for taxonomic remarks in respect of ongoing molecular now. work are also discussed. Phelsuma sundbergi longinsulae (Fig. 14) REPTILIA Localities: Fregate 114; Mahé 16-18, 20, 22, 24- GEKKONIDAE 26, 25B, 29, 31, 34-36, 39, 40, 44, 45, 47-52, 55, Phelsuma 59, 62, 64-68, 68B; Cosmoledo 8; Cerf 69, 70; The most conspicuous reptile group of the Silhouette 71, 75, 76; North Island 115. In Mahé, Seychelles, Phelsuma are brightly coloured, where it co-exists with P. astriata, P. sundbergi generally diurnal geckos, occurring in a wide seems to be much more abundant (at least it is range of habitats from high mountain forest to much more frequently observed), with P. astriata banana and coconut plantations. There are clearly being much less conspicuous and predominantly two species in the granitic islands (Phelsuma found at higher altitudes in the canopy. sundbergi and Phelsuma astriata) and another one present on the southern atolls (Phelsuma abbotti). Phelsuma astriata (Fig. 11) Alpha-taxonomy is still not clear for the group, Localities: Mahé 29, 33, 39, 45, 53, 55, 59; Praslin mainly due to the highly variable nature of dorsal 99, 100, 102, 103, 104, 105, 107, 109, 110, 113; coloration patterns across the islands. A third La Digue 93, 94, 95, 99; Curieuse 80, 81, 82; Cerf form is sometimes recognised as a full species 70; Cousine 87, 89; Grand Soeur 92; Fregate 114; (Phelsuma longinsulae) and as many as three to Silhouette 74, 75; Aride 79; Astove 7; Alphonse 13. four subspecies are sometimes recognized within Cheke (1984) described P. astriata from Fregate (« P. astriata and P. sundbergi respectively. In this Fregate form ») as an intermediate form between report only two subspecies within P. sundbergi (P. P. a. astriata (Mahé group, Silhouette, Astove and sundbergi and P. longinsulae) are provisionally Alphonse) and P. a. semicarinata (Praslin group, used, and no subspecific divisions within P. D’Arros and St. Joseph). Ongoing studies with astriata, recognizing only the forms that are easily molecular markers should reveal patterns of genetic distinguishable in the field. Phelsuma sundbergi variation within this group and provide useful and P. astriata are endemic to the Seychelles and information for future taxonomic reappraisals. 22 Number 110 - Herpetological Bulletin [2009] Herpetofaunal distribution, Seychelles Phelsuma abbotti (Fig. 1) Hemidactylus Localities: Aldabra 2, 3, 6; Assumption 1. A At least two Hemidactylus species occur in the nortwestern Malagasy species. Traditionally two Seychelles: Hemidactylus mercatorius (sensu endemic subspecies are recognized as inhabiting Kluge 2001) and Hemidactylus frenatus. Records the southern atolls of the Seychelles: P. a. abbotti, for a third species, Hemidactylus brookii, exist for in Aldabra and P. a. sumptio, in Assumption. Both Desroches (Amirantes) but were not confirmed by seem to exist at high densities but are presently surveys in this report. The relationship between considered as “Vulnerable” due to their restricted the Seychelles populations of H. mercatorius range (Gerlach, 2007). This species is usually with both East African and Malagasy specimens, observed on trunks, perching at low heights within and with East African Hemidactylus mabouia was tropical dry forest. recently studied using molecular data (Rocha et al., in press). Ailuronyx The genus is endemic to the Seychelles. Hemidactylus mercatorius (Fig. 9) The previous Malagasy record of Ailuronyx Localities: Mahé 59, 68; Assumption 1; Aldabra 2, trachygaster (1981) is probably erroneous (Bauer, 3, 5, 6; Astove 7; Cosmoledo 8-11. Abundant and 1990). The species is believed to have a pre- widespread in the southern atolls, there are some quaternary age in the islands (Cheke, 1984)