Taxonomic subdivisions within the fossorial skink subfamily Acontinae (Squamata: Scincidae) reconsidered: A multilocus perspective

Despite recent molecular systematic studies on the fossorial southern African skink subfamily Acontinae, evolutionary relationships among the three genera remain unresolved and disputed. Among these, the most recent study suggests that both Typhlosaurus and Acontias are paraphyletic, contrasting earlier results that suggest the presence of two divergent clades within Acontias. Here we further investigate the evolutionary relationships in the limbless fossorial southern African subfamily Acontinae with partial sequenced data derived from four mitochondrial loci (16S rRNA, 12S rRNA, cytochrome oxidase I and cytochrome b), as well as two nuclear protein coding loci (c-mos and RAG-1), in an attempt to clarify evolutionary relationships. Phylogenetic results derived from combined data analyses (comprising all six loci and totalling ∼3.1 kb) using maximum parsimony, maximum likelihood and Bayesian inferences converged on the same topology. The resulting phylogeny showed Typhlosaurus as monophyletic, while the monotypic genus Acontophiops was nested intermediate to two reciprocally monophyletic Acontias clades. These two Acontias clades can be distinguished on the basis of a number of morphological, morphometric and biogeographical characters, underscoring the presence of two distinct groups. In the present study, we propose the following taxonomic changes based on the multilocus phylogeny. We retain the genus name Acontias for the medium- and large-bodied skinks in clade 2 comprising all taxa in the Acontias meleagris complex as well as Acontias plumbeus, Acontias gracilicauda gracilicauda, Acontias breviceps, Acontias percivali percivali and Acontias percivali occidentalis. We designate a new genus Microacontias gen. nov. for the reciprocally monophyletic taxa in clade 1 comprised of all the small-bodied taxa that include Microacontias litoralis, Microacontias lineatus lineatus, Microacontias lineatus grayi and Microacontias lineatus tristis. We examine the evolution of characters used in the taxonomy of the Acontinae and suggest that symplesiomorphic morphological characters among fossorial taxa have been an impediment to understanding the evolution of this subfamily. This study underscores the importance of the application of multiple molecular markers (both nuclear and mitochondrial) in determining the taxonomic diversity among fossorial skinks and emphasizes the application of phylogenetics in defining synapomorphic (shared derived) features. © 2006 The Norwegian Academy of Science and Letters.