Molecular phylogeny of the tribe Philodryadini Cope, 1886 (Dipsadidae: Xenodontinae): Rediscovering the diversity of the South American Racers

Abstract

South American racers of the tribe Philodryadini are a widespread and diverse group of Neotropical snakes with a complex taxonomic and systematic history. Recent studies failed to present a robust phylogenetic hypothesis for the tribe, mainly due to incomplete taxon sampling. Here we provide the most extensive molecular phylogenetic analysis of Philodryadini available so far, including 20 species (83% of the known diversity) from which six were not sampled previously. Our results reveal that Philodryadini is not monophyletic, but instead includes a central Andean clade formed by Philodryas simonsii, P. tachymenoides, and P. amaru, and a southern and cis-Andean clade including all remaining philodryadines. This discovery requires resurrection of two genera as well as erection of a new tribe of Xenodontinae for the central Andean clade. Within the southern and cis-Andean radiation, our analyses resolve a basal dichotomy separating two main lineages: Clade A, containing the Common Green Racers P. laticeps and P. viridissima and the South American Vine snakes P. georgeboulengeri and P. argentea; and Clade B, including the remaining species of Philodryas sensu stricto. We resurrect the genera Chlorosoma and Xenoxybelis to better represent the monophyly of lineages within the southern and cis-Andean clade.