A comprehensive phylogeny of night adders (Causus)

African night adders (Causus) are an enigmatic group of viperid snakes in the subfamily Viperinae. These snakes have a suite of unusual characters atypical of other species of vipers (e.g., oviparous reproduction, round pupils) but are firmly placed within the Viperinae, sister to all other genera. The genus is widespread across sub-Saharan Africa, with some species having severely fragmented distributions, potentially suggesting cryptic lineages. Others have extremely large ranges, which is unusual for a medium-sized snake (< 1 m), possibly suggesting unrecognised cryptic lineages or unacknowledged species boundaries. We therefore constructed a species-level phylogeny that included seven of the eight recognised species. We used three molecular markers (two mitochondrial: 16S and Cyt-b, one nuclear: c-mos) and applied both Bayesian and likelihood analyses for multiple representatives of each species from across their respective ranges. The phylogeny suggests that each of the described species are monophyletic, however, we recovered several clades in some species with fragmented distributions (C. bilineatus, C. defilippii), as well as within some widespread species (C. rhombeatus, C. maculatus). Finally, our results support the recent elevation of C. nasalis from southwestern Angola, which had not been confirmed through genetic analyses previously.