A molecular phylogeny of four endangered Madagascar tortoises based on MtDNA sequences.

摘要: Four of the five tortoise species in Madagascar,Pyxis arachnoides, P. planicauda, Geochelone radiata,andG. yniphora,are endemic and on verge extinction. Their phylogenetic relationships remain controversial unresolved. Here we address phylogeny this group using DNA sequences for 12S 16S rDNA cytbgenes mitochondrial DNA. As outgroups used two ofGeochelone, pardalis(mainland Africa) andnigra(Galapagos), as well a more distant North American tortoise,Gopherus polyphemus.We conclude that twoPyxisspecies are sister taxa imbedded genusGeochelone,rendering latter genus paraphyletic. There is moderate support status MadagascarGeocheloneand monophyletic origin all four endemics, suggesting single colonization island. The separation Madagascar from other land masses (90–165 mya) predates tortoises (estimated to be 14–22 mya). This suggests founding by rafting, process known have occurred with tortoises. derived morphological divergence thePyxisspecies relatively short period time (13–20 my) stands contrast notoriously slow rate evolution most lineages Chelonia.