A taxonomic re-assessment of Oligodon cinereus (Günther, 1864) (Squamata, Serpentes, Colubridae) populations from southern Indochina

The ashy kukri snake Oligodon cinereus (Günther, 1864) is a widely distributed and morphologically variable species found throughout mainland Southeast Asia. In this paper, we re-assessed the taxonomic status of O. cinereus populations found in southern Indochina (southern Vietnam, Cambodia, and southern Laos), including the recently described Cat Tien kukri snake Oligodon cattienensisVassilieva et al., 2013, which was previously confused with this species. Phylogenetic analyses using mitochondrial DNA from the 12S–16S ribosomal subunit and cytochrome b gene revealed that O. cattienensis is embedded in a mixed clade containing samples of the subspecies O. cinereus pallidocinctus, which bears a dorsal color pattern with white crossbars and black edges. This clade forms a strongly supported sister group with a topotypic sample of O. cinereus cinereus, representing populations bearing a uniform dorsal color pattern and slight reticulate markings, however the genetic divergence between the two clades is very low. The morphological characters used to distinguish O. cattienensis from O. cinereus sensu lato broadly overlap and supposed differences in hemipenial morphology between the two taxa are due to outdated terminologies used to describe the organ. We relegate both O. cattienensis and O. cinereus pallidocinctus to the junior synonymy of O. cinereus and consider all color patterns of this species found near the type locality in Cambodia, southern Laos, and southern Vietnam to represent O. cinereus sensu stricto. Future integrative investigations across the range of O. cinereus sensu lato are needed to resolve the status of the remaining subspecies and synonyms associated with this taxon. Problems associated with hemipenial morphology and Oligodon systematics are also discussed.