Stable climate corridors promote gene flow in the Cape sand snake species complex (Psammophiidae)

Abstract

Climate shifts during the Quaternary Period have driven changes in regional range dynamics for many species, influencing population structure of species and in some cases promoting speciation. Within southern Africa, the psammophine snakes Psammophis trinasalis and P. namibensis were historically considered subspecies of P. leightoni but were elevated to species rank based on ecological differences. Preliminary phylogenetic analyses suggested intraspecific, not interspecific genetic variation between these taxa, but this finding was based on very limited data and could not be confirmed. To assess the level of genetic differentiation within the P. leightoni species complex, we explored the evolutionary history of these snakes by combining phylogenetic analyses, species distribution modelling and an examination of morphology. We generated a comprehensive, multi-gene phylogeny for Psammophis that included wider geographic sampling of the three species in the complex. Using this phylogeny, Bayesian and distance-based species delimitation analyses showed intraspecific, not interspecific divergences between taxa in the complex, suggesting that they collectively represent a single taxon. Furthermore, non-metric multidimensional scaling analysis of scalation characters showed no differences between the species. Moreover, palaeo-modelling at three time periods since the last interglacial period suggest that there have been varying levels of connectivity between these taxa, which has likely facilitated gene flow between them. Given the evidence, we propose that the P. leightoni complex represents a single species and therefore formally synonymise the three species.

An updated herpetofaunal species inventory of Iona National Park in southwestern Angola

“…The specimen from Espinheira was first reported by Branch (2018) and it was morphologically ascribed to L. namibianum based on the diagnostic lack of contact between the first supralabial and postnasal (versus contact in L. hellmichi) (Broadley 1991). This is also the only known record from Angola, extending its known distribution range northwards by ~180 km (Branch 2018; (Taft et al 2021). A preliminary phylogenetic analysis with unpublished material from Namibia (C. Keates unpubl.…”

“…Biology and distribution. As a consequence of the reevaluation of the species (Taft et al 2021), this species now has a large known distribution in the western arid region from Angola to South Africa, being commonly found in dunes of the Namib Desert, moving actively during the day between small patches of vegetation (Branch 2018). The specimens reported here from Iona NP were always found during the day by following characteristic tracks visible in the soft sand of the desert dunes region (Fig.…”

Phylogeny and phylogeography of chelonians from sub-Saharan Africa—A review of current knowledge in tribute to Margaretha D. Hofmeyr

“…The lack of structure is likely due to stability of its range throughout the Pleistocene. Similarly, co-distributed snake species (e.g., Bitis arietans, Psammophis leightoni) do not show notable phylogeographic structure within the central arid regions of southern Africa, and this also has been attributed to climatic stability (Barlow et al 2013;Taft et al 2022). In addition, genetic clades of the puff adder (B. arietans) show a contact zone in the Limpopo area (Barlow et al 2013) where the two Pelomedusa species also make geographic contact.…”

“…While integration of different data types has been carried out for P. tentorius to assess species level diversity (Zhao et al 2021b), it is also imperative that a species delimitation approach within a full phylogenetic framework is applied (Reid and Carstens 2012;Carstens et al 2013) that includes congeners. For example, confusing taxonomy and lack of an explicit species concept had plagued taxonomic assessments of some reptiles in southern Africa, but teasing out species can be accomplished when a clear concept is circumscribed in advance, and a phylogenetic approach is used to assess species (e.g., Taft et al 2022;Tolley et al 2022aTolley et al , 2022b).…”