Molecular phylogeny of elapid snakes and a consideration of their biogeographic history

Abstract

Evolutionary relationships among the major elapid clades, particularly the taxonomic position of the partially aquatic sea kraits (Laticauda) and the fully aquatic true sea snakes have been the subject of much debate. To discriminate among existing phylogenetic and biogeographic hypotheses, portions of both the 16S rRNA and cytochromebmitochondrial DNA genes were sequenced from 16 genera and 17 species representing all major elapid snake clades from throughout the world and two non-elapid outgroups. This sequence data yielded 181 informative sites under parsimony. Parsimony analyses of the separate data sets produced trees of broad agreement although less well supported than the single most parsimonious tree resulting from the combined analyses. These results support the following hypotheses: (1) the Afro-Asian cobra radiation forms one or more sister groups to other elapids, (2) American and Asian coral snakes form a clade, corroborating morphological studies, (3)Bungarusforms a sister group to the hydrophiines comprised ofLaticauda, terrestrial Australo-Papuan elapids and true sea snakes, (4)Laticaudaand true sea snakes do not form a monophyletic group but instead each group shares an independent history with terrestrial Australo-Papuan elapids, corroborating previous studies, (5) a lineage of Melanesian elapids forms the sister group toLaticauda, terrestrial Australian species and true sea snakes. In agreement with previous morphologically based studies, the sequence data suggests thatBungarusandLaticaudarepresent transitional clades between the elapine ‘palatine erectors’ and hydrophiine ‘palatine draggers’. Both intra and inter-clade genetic distances are considerable, implying that each of the major radiations have had long independent histories. I suggest an African, Asian, or Afro-Asian origin for elapids as a group, with independent Asian origins for American coral snakes and the hydrophiines.