Inclusion of nuclear intron sequence data helps to identify the Asian sister group of New World pitvipers.

Despite much effort towards resolving the molecular phylogenetic tree for pitvipers, some aspects remain unresolved. In particular, the sister group of the diverse New World radiation has remained impossible to identify with any certainty. In this study, which for the first time includes nuclear intron data from all major groups of Asian pitvipers as well as representatives of the New World radiation, Bayesian inference allows Gloydius to be identified as the most likely sister group to the New World radiation and sheds light on other ambiguous relationships among the Old World pitvipers. The sister group relationship of "Ovophis"okinavensis and "Trimeresurus"gracilis is confirmed by the addition of nuclear genes, and we hypothesise that they form a sister group to the Gloydius+New World clade, best supported when the phylogenetic signal from gaps is included in the form of a simple-coded matrix.