Phylogeny and species delimitation in an iconic snake genus: the African mambas (Serpentes: Elapidae: Dendroaspis)

Abstract

The African mambas (Dendroaspis) comprise an iconic genus of four large-bodied, highly venomous elapid snakes: the black mamba (D. polylepis) from open formations across sub-Saharan Africa is comprised of two allopatric populations, and three species of green mamba (D. angusticeps, D. jamesoni, and D. viridis) from tropical and sub-tropical forests. Dendroaspis angusticeps occurs in multiple isolated forest patches, and the presence of cryptic species within D. angusticeps has been suggested. The striking coloration of the three green species, a trait unique among elapids, suggests their monophyly to the exclusion of D. polylepis. We generated a dated, multilocus phylogeny of the mambas and assessed species boundaries. Species distribution modelling (SDM) was used to assess the past and present potential connectivity between allopatric populations of D. angusticeps and D. polylepis. The phylogeny suggests that diversification of the crown clade began c. 6 Mya and, contrary to previous suggestions, we found no convincing signal of species-level diversification within D. polylepis or D. angusticeps. The hypothesis of green mamba monophyly was rejected, with D. angusticeps being sister to D. polylepis. The SDMs suggested that allopatric populations of D. polylepis and D. angusticeps were historically connected, and that their vicariance is recent.