A preliminary analysis of phylogenetic relationships and biogeography of the dangerously venomous Carpet Vipers, Echis (Squamata, Serpentes, Viperidae) based on mitochondrial DNA sequences

摘要

Phylogenetic analysis of 1117 bp of mitochondrial DNA sequences (731 bp of cytochrome b and 386 bp of 16S rRNA) indicate that Echis consists of four main clades: E. ocellatus, and the E. coloratus, E. pyramidum, and E. carinatus groups. In the E. coloratus group, E. coloratus itself shows substantial genetic divergence from E. omanensis, corroborating their separate species status. In the E. pyramidum clade, E. pyramidum from Egypt and E. leucogaster from West Africa are genetically very similar, even though samples are separated by 4000 km. South Arabian populations of the E. pyramidum group are much better differentiated from these and two species may be present, animals from Dhofar, southern Oman probably being referable to E. khosatzkii. In the E. carinatus group, specimens of E. carinatus sochureki and E. multisquamatus are very similar in their DNA. The phylogeny indicates that the split between the main groups of Echis was followed by separation of African and Arabian members of the E. pyramidum group, and of E. coloratus and E. omanensis. The last disjunction probably took place at the lowlands that run southwest of the North Oman mountains, which are likely to have been intermittently covered by marine incursions; they also separate the E. pyramidum and E. carinatus groups and several sister taxa of other reptiles. The E. carinatus group may have spread quite recently from North Oman into its very extensive southwest Asian range, and there appears to have been similar expansion of E. pyramidum (including E. leucogaster) in North Africa. Both these events are likely to be associated with the marked climatic changes of the Pleistocene or late Pliocene. Similar dramatic expansions have also recently occurred in three snake species in Iberia.