Phylogenetics and Integrative Taxonomy of African Water Snakes (Squamata: Colubridae: Grayia)
Grayia is a genus of relatively large (1.5 – 2.5 m) aquatic Afrotropical snakes. Recent molecular phylogenies recovered Grayia in its own distinct subfamily (Grayiinae), which was strongly supported as the sister group to Colubrinae. Because tropical African snakes are generally understudied, the relationships within Grayia are poorly known. Due to high degrees of intra- and interspecies variation, identification is often difficult and previous studies involving Grayia included misidentified specimens in other genera. The goal of this study is to create a phylogenetic tree that can be used to understand the relationships and taxonomy of Grayia via an integrative taxonomic approach that combines molecular and morphological data. Two nuclear (BDNF, NT3) and four mitochondrial genes (COI, cyt b, 16S and ND4) were used to construct phylogenetic trees with Maximum likelihood and Bayesian inference methods; outgroups included the genera Calamaria, Sibynophis, and Masticophis. The phylogenetic trees recovered two clades, Grayia caesar + G. tholloni and G. ornata + G. smithii, which the time-calibrated BEAST analysis estimated to have diverged from each other in the mid-Oligocene. Grayia ornata was found to consist of two distinct subclades, one from west and one from east, of the Congo and Ubangi Rivers. This suggests that these large rivers may be more of a barrier than previously believed. Molecular and morphological evidence supports a new cryptic species of Grayia from the upper and middle Congo River and its tributaries. This new species is estimated to have diverged from its nearest sister species, G. ornata, in the mid- to late Miocene—which coincides with the divergence dates of sister taxa within other Central African snake genera (Boaedon [Family Lamprophiidae], Atheris [Family Viperidae], and Polemon [Family Lamprophiidae]).
Chaney, Teslin Susann, "Phylogenetics and Integrative Taxonomy of African Water Snakes (Squamata: Colubridae: Grayia)" (2023). ETD Collection for University of Texas, El Paso. AAI30425325.