Maluti Mystery: A systematic review of Amietia vertebralis (Hewitt, 1927) and Strongylopus hymenopus (Boulenger, 1920) (Anura: Pyxicephalidae)

Abstract

The taxonomic status of Amietia vertebralis and Strongylopus hymenopus, two frogs restricted to the Maluti-Drakensberg highlands in southern Africa, is unclear. Here, morphological examination and phylogenetic analyses elucidate the systematic position of these two species. Type specimens of both species were examined and compared with more recent collections to clarify their identity. These comparisons revealed discrepancies between the original application of these names and their current usage. The holotype and original description of A. vertebralis match specimens from an extant population at that species� type locality that are currently assigned to S. hymenopus. Furthermore, the type specimen of S. hymenopus is of uncertain provenance and does not match well with either of the forms currently associated with these names. We assessed both intraspecific and interspecific variability using DNA sequence data. Broad sampling of the form currently assigned to A. vertebralis revealed very little genetic variation thereby dispelling the hypothesis that this is a compound taxon. The generic placement of both species within the family Pyxicephalidae was resolved using a combined dataset of mitochondrial 16S rDNA and nuclear RAG1 gene sequences. The form currently recognised as S. hymenopus was excluded from the otherwise monophyletic genus Strongylopus, and was placed instead within Amietia. Based on these data a revised application of both species names is recommended here. Populations currently assigned to Amietia vertebralis are referred to Amietia umbraculata and those attributed to Strongylopus hymenopus are referred instead to Amietia vertebralis.