Systematics of the Thirteen-scaled Green Snake Philothamnus carinatus (Squamata: Colubridae), with the description of a cryptic new species from Central and East Africa

Abstract

Recent molecular phylogenies of African Green Snakes suggested the geographically widespread species Philothamnus carinatus includes at least two distinct lineages. We utilised an integrative taxonomic approach with morphological and genetic data to reconcile the taxonomic status of these cryptic lineages, including the recently described taxon P. brunneus from West Africa. We sequenced three mitochondrial (16S, cyt b and ND4) and two nuclear (c-mos and RAG1) genes from several Central African populations of P. carinatus and combined our data with other closely related species to infer a maximum likelihood phylogenetic tree with IQ-TREE. Our results are consistent with previous studies that showed P. cf. carinatus populations from Democratic Republic of the Congo (DRC) represent a cryptic lineage that is distinct from P. carinatus sensu stricto in Cameroon, Central African Republic, Equatorial Guinea (including Bioko Island), Gabon, eastern Nigeria, Republic of the Congo, and extreme western DRC. In our preferred tree, P. brunneus (limited to 16S molecular data) was recovered as a relatively long branch in a moderately supported clade with P. carinatus sensu stricto, whereas P. cf. carinatus populations from northern Angola, most of DRC, and East Africa (Burundi, Kenya, Rwanda, Tanzania and Uganda) were described as a new species. A possible hybrid population between south-eastern Cameroon and north-western DRC is consistent with an increasing body of evidence suggesting the Ubangi River might represent a hybrid zone area.