Project description:We present 10 nearly complete mitochondrial genomes of the extinct tortoise Chelonoidis alburyorum from the Bahamas. While our samples represent morphologically distinct populations from six islands, their genetic divergences were shallow and resembled those among Galápagos tortoises. Our molecular clock estimates revealed that divergence among Bahamian tortoises began ~ 1.5 mya, whereas divergence among the Galápagos tortoises (C. niger complex) began ~ 2 mya. The inter-island divergences of tortoises from within the Bahamas and within the Galápagos Islands are much younger (0.09-0.59 mya, and 0.08-1.43 mya, respectively) than the genetic differentiation between any other congeneric pair of tortoise species. The shallow mitochondrial divergences of the two radiations on the Bahamas and the Galápagos Islands suggest that each archipelago sustained only one species of tortoise, and that the taxa currently regarded as distinct species in the Galápagos should be returned to subspecies status. The extinct tortoises from the Bahamas have two well-supported clades: the first includes one sample from Great Abaco and two from Crooked Island; the second clade includes tortoises from Great Abaco, Eleuthera, Crooked Island, Mayaguana, Middle Caicos, and Grand Turk. Tortoises belonging to both clades on Great Abaco and Crooked Island suggest late Holocene inter-island transport by prehistoric humans.
Project description:Already too late? Massive trade in Indian star tortoises (Geochelone elegans) might have wiped out its phylogeographic differentiation
Project description:Ancient mitochondrial DNA sequences were used for investigating the evolution of an entire clade of extinct vertebrates, the endemic tortoises (Cylindraspis) of the Mascarene Islands in the Indian Ocean. Mitochondrial DNA corroborates morphological evidence that there were five species of tortoise with the following relationships: Cylindraspis triserrata ((Cylindraspis vosmaeri and Cylindraspis peltastes) (Cylindraspis inepta and Cylindraspis indica)). Phylogeny indicates that the ancestor of the group first colonized Mauritius where speciation produced C. triserrata and the ancestor of the other species including a second sympatric Mauritian form, C. inepta. A propagule derived from this lineage colonized Rodrigues 590 km to the east, where a second within-island speciation took place producing the sympatric C. vosmaeri and C. peltastes. A recent colonization of Réunion 150 km to the southwest produced C. indica. In the virtual absence of predators, the defensive features of the shells of Mascarene tortoises were largely dismantled, apparently in two stages. 'Saddlebacked' shells with high fronts evolved independently on all three islands. This and other features, such as a derived jaw structure and small body size, may be associated with niche differentiation in sympatric species and may represent a striking example of parallel differentiation in a large terrestrial vertebrate. The history of Mascarene tortoises contrasts with that of the Galápagos, where only a single species is present and surviving populations are genetically much more similar. However, they too show some reduction in anti-predator mechanisms and multiple development of populations with saddlebacked shells.
Project description:Russell’s viper (Daboia russelii) (RV), a category I medically important snake as well as a member of the “Big Four”, is responsible for a heavy toll of snake bite mortality and morbidity in Indian sub-continent. Epidemiological studies suggest highest incidence of RV envenomation in eastern India (EI). In this study the RV venom proteomes from Burdwan and Nadia, the two districts of West Bengal, eastern India was deciphered for the first time using tandem mass spectrometry analysis.
Project description:The living tree sloths Choloepus and Bradypus are the only remaining members of Folivora, a major xenarthran radiation that occupied a wide range of habitats in many parts of the western hemisphere during the Cenozoic, including both continents and the West Indies (Antilles). To date, molecular evidence has played only a minor role in folivoran systematics, as most recently-extinct species lived in places not conducive to DNA preservation. Here we utilize collagen sequence information to assess the relationships of tree sloths to a large sample (13 species) of extinct Quaternary folivorans.
Project description:Before humans arrived, giant tortoises occurred on many western Indian Ocean islands. We combined ancient DNA, phylogenetic, ancestral range, and molecular clock analyses with radiocarbon and paleogeographic evidence to decipher their diversity and biogeography. Using a mitogenomic time tree, we propose that the ancestor of the extinct Mascarene tortoises spread from Africa in the Eocene to now-sunken islands northeast of Madagascar. From these islands, the Mascarenes were repeatedly colonized. Another out-of-Africa dispersal (latest Eocene/Oligocene) produced on Madagascar giant, large, and small tortoise species. Two giant and one large species disappeared c. 1000 to 600 years ago, the latter described here as new to science using nuclear and mitochondrial DNA. From Madagascar, the Granitic Seychelles were colonized (Early Pliocene) and from there, repeatedly Aldabra (Late Pleistocene). The Granitic Seychelles populations were eradicated and later reintroduced from Aldabra. Our results underline that integrating ancient DNA data into a multi-evidence framework substantially enhances the knowledge of the past diversity of island faunas.
