How many species does the Psammobates tentorius (tent tortoise) species complex (Reptilia, Testudinidae) comprise? A taxonomic solution potentially applicable to species complexes

Abstract

We examined morphometric differentiation in the highly polymorphic and taxonomically confusing Psammobates tentorius (tent tortoise) species complex in southern Africa, using morphological data together with previously published DNA sequence and microsatellite DNA data. We used the approximate Bayesian computation-based simulation analysis to test alternative phylogenetic hypotheses supported by different markers, using a total evidence dataset for the tent tortoise species complex. The results supported a scenario, which is better and more inclusive in explaining its genealogical history. Our total evidence-based Bayesian BPP species delimitation analysis (mtDNA + nDNA + morphology) suggested a seven species scheme should be applied to the P. tentorius species complex. Nonetheless, based on comparative results obtained from sequence, microsatellite, ecological niche, and morphological data, a four-species scheme (among the seven mtDNA clades) appears to be the best taxonomic solution for the systematic puzzle of the P. tentorius species complex, namely, “C1 + C4 + C5 + C7,” “C3,” “C2,” and “C6.” We detected several possible hybridizations between C1 and C2 in their intergradation zone that confirmed the possible cross-over between them. Lastly, we provide a summarized flow chart of the analyses carried out for determining the optimal taxonomic solution for this phenotypically difficult group, as it may also be useful for resolving complex taxonomic issues in other species groups.