Taxonomy and geographic distribution of Malagasy frogs of the Gephyromantis asper clade, with description of a new subgenus and revalidation of Gephyromantis ceratophrys

We integrate molecular, bioacoustic and morphological data to provide a systematic revision of the frogs classified in the Gephyromantis asper clade (Anura: Mantellidae), endemic to Madagascar. Based on concordant differentiation in a mitochondrial and a nuclear gene (16S rRNA and Rag1) we distinguish six different species in this clade: G. ambohitra, G. asper, G. tahotra, G. spinifer, G. ceratophrys bona species, and an undescribed species. Gephyromantis ceratophrys (Ahl, 1929) is resurrected from the synonymy of G. asper and refers to the southernmost populations previously assigned to that species (i.e., from Ranomafana National Park in the southern central east of Madagascar). We provide several new geographical records verified by molecular sequence identity: G. asper is confirmed from the localities Anjozorobe, Mandraka, and Tsinjoarivo; G. spinifer is confirmed from Pic Ivohibe, a record previously considered questionable and representing the northernmost locality known for this species; G. ambohitra is recorded from the Masoala Peninsula, extending its known distribution range eastward; and G. tahotra (previously only known from its type locality Marojejy) is confirmed for the Tsaratanana and Sorata Massifs. An undescribed species of the group occurs at sites south and southwest of the Tsaratanana massif. It is differentiated in mitochondrial and nuclear DNA, but no bioacoustic and insufficient morphological data are thus far available for its formal taxonomic description. Because species in the G. asper clade, within Gephyromantis, are phylogenetically distant from other species of the subgenus Duboimantis, we propose a new subgenus Asperomantis for this clade of Malagasy rainforest frogs. Most individuals belonging to this subgenus are easily distinguished from other species in the genus Gephyromantis and most other mantellids by the presence of a light spot in or near the centre of the tympanum.