Origin and evolutionary relationships of giant Galápagos tortoises
AUTOR(ES)
Caccone, Adalgisa
FONTE
The National Academy of Sciences
RESUMO
Perhaps the most enduring debate in reptile systematics has involved the giant Galápagos tortoises (Geochelone nigra), whose origins and systematic relationships captivated Charles Darwin and remain unresolved to this day. Here we report a phylogenetic reconstruction based on mitochondrial DNA sequences from Galápagos tortoises and Geochelone from mainland South America and Africa. The closest living relative to the Galápagos tortoise is not among the larger-bodied tortoises of South America but is the relatively small-bodied Geochelone chilensis, or Chaco tortoise. The split between G. chilensis and the Galápagos lineage probably occurred 6 to 12 million years ago, before the origin of the oldest extant Galápagos island. Our data suggest that the four named southern subspecies on the largest island, Isabela, are not distinct genetic units, whereas a genetically distinct northernmost Isabela subspecies is probably the result of a separate colonization. Most unexpectedly, the lone survivor of the abingdoni subspecies from Pinta Island (“Lonesome George”) is very closely related to tortoises from San Cristóbal and Española, the islands farthest from the island of Pinta. To rule out a possible recent transplant of Lonesome George, we sequenced DNA from three tortoises collected on Pinta in 1906. They have sequences identical to Lonesome George, consistent with his being the last survivor of his subspecies. This finding may provide guidance in finding a mate for Lonesome George, who so far has failed to reproduce.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=23929Documentos Relacionados
- Giant tortoises are not so slow: Rapid diversification and biogeographic consensus in the Galápagos
- Evolutionary aspects on the origin, distribution and ramifications of the ischiadicus nerve in the giant anteater (Myrmecophaga tridactyla)
- Ancient mitochondrial DNA and morphology elucidate an extinct island radiation of Indian Ocean giant tortoises (Cylindraspis).
- Evolutionary Relationships and Systematics of the Alphaviruses
- Comparative Biology and Evolutionary Relationships of Tree Shrews