Unraveling the diversification and systematic puzzle of the highly polymorphicPsammobates tentorius(Bell, 1828) complex (Reptilia: Testudinidae) through phylogenetic analyses and species delimitation approaches

Abstract

The high level of phenotypic diversity in southern African tent tortoises (Psammobates tentorius complex) has for decades prevented systematists from developing a stable taxonomy for the group. Here, we used a comprehensive DNA sequence dataset (mtDNA: Cytb, ND4, ND4 adjacent tRNA-His, and tRNA-Ser, 12S, 16S; and nDNA:PRLR gene) of 455 specimens, and the latest phylogenetic and species delimitation analytical procedures, to unravel the long-standing P. tentorius complex systematic puzzle. Our results for mtDNA and nDNA were incongruent, with the poorly supported nDNA phylogeny differentiating the three recognized subspecies, and showing potential hybridization in some regions. In contrast, the concatenated mtDNA phylogeny identified seven operational taxonomic units, with strong support. Clades 1, 4, 5, and 7 corresponded to tortoises identified as P. t. tentorius, clade 3 to P. t. trimeni, and clades 2 and 6 to P. t. verroxii. Our analyses showed conflicting topologies for the placement of C6 (P. t. verroxii north of the Orange River), with stronger support for it being sister to C2 + C3 than to the other clades. Clades 1, 2, and 6 had significantly higher genetic diversity than clades 3, 4, 5, and 7, perhaps because these clades inhabit substantially larger areas. The potential for future cladogenic radiations seems high in C1 and C6, particularly in C6 for which the within-clade diversification level was highest. Further research involving microsatellite DNA, phylogeographic evaluations, and morphological variation among clades is crucial for understanding the adaptive radiation of the P. tentorius complex and for modifying their taxonomy. K E Y W O R D SmtDNA, phylogeny, reptile, southern Africa, tent tortoise | 309 ZHAO et Al.

Climatic and topographic changes since the Miocene influenced the diversification and biogeography of the tent tortoise (Psammobates tentorius) species complex in Southern Africa

“…Our study suggests that Ptt-B, Ptt-C, Ptt-A and Ptt-D are a single candidate species but with multiple conservation units, whilst, Ptr, Pv-A and Pv-B are three different species with different conservation units. This study together with the ndings in [40] provides strong evidence that P. tentorius requires a taxonomic revision, which would impact the Red List Assessment of the species. As a species, the IUCN currently lists P. tentorius as "Near Threatened" [95] and P. t. trimeni as "Endangered" [95].…”

“…However, the estimated gene ow level was comparatively high between Ptt-B and Ptt-C, suggesting that the degree of genetic isolation between them was low. Nonetheless, the genetic difference between the two clades was found to be signi cant, based on multiple species delimitation analyses in Zhao et al [40], and was attributed to the western section of the GE completely separating them geographically. This evidence supports the genetic distinctiveness of Ptt-B and Ptt-C.…”

“…3b-c). According to (Zhao et al, [40]), some of the species delimitation analyses also revealed that the species boundary between Ptt-B and Ptt-C was not clear, thus treating Ptt-B and Ptt-C as the same candidate species is certainly reasonable. However, treating Ptt-A and Ptt-D as a single candidate species or OTU, will con ict with our phylogenetic structure, since the DNA sequence based phylogeny did not support Ptt-A and Ptt-D as a sister group.…”

“…Lineage turnover rate was also low for the Nama Karoo, as well as for Ptt-B and Pv-B associated with this biome, but the turnover rate for Pv-A in the Nama Karoo north of the OR was high. The region and biome analyses were not very informative possibly because the division of characters oversimpli ed the great climatic and topographic heterogeneity of the Southern African landscape [40,81].…”

“…There are substantial distribution range overlaps among the three subspecies, with seemingly hybrid individuals found in the intergradation zones, though many are believed to be misidenti cations [24,35]. In a subsequent study, Zhao et al [40] used six mtDNA markers, one nDNA marker, and multiple species delimitation methods, to investigate the phylogenetic structure of P. tentorius. The mtDNA phylogeny distinguished seven monophyletic clades with strong support, with each clade occurring in a distinct geographic region (Fig.…”