Indian Ocean Giant Tortoises: Their Systematics and Island Adaptations

摘要: Although wild populations are now confined to Aldabra, giant tortoises were originally present on many other Indian Ocean islands. All belong the genus Geochelone but referable two distinct subgenera, Cylindraspis in Mascarene islands and Aldabrachelys Madagascar, Seychelles neighbouring These distinguishable by skull nasal structure, degree of shell ankylosis structure plastron. Neither group has obvious close relatives areas. tortoises, which completely extinct, comprised several species: G. vosmaeri smaller peltastes Rodrigues, inepta triserrata Mauritius, what should probably be called indica Reunion. seem one species, gigantea appears have shown some geographical variation. Madagascar had grandidieri another usually named abrupta may well conspecific with was possibly source Aldabra populations. Many distinctive features Galapagos interpretable as adaptations peculiar environment ocean islands, particularly their lack big predators competing herbivores.