The first endemic West African vertebrate family – a new anuran family highlighting the uniqueness of the Upper Guinean biodiversity hotspot

Abstract

Background

Higher-level systematics in amphibians is relatively stable. However, recent phylogenetic studies of African torrent-frogs have uncovered high divergence in these phenotypically and ecologically similar frogs, in particular between West African torrent-frogs versus Central ( Petropedetes) and East African ( Arthroleptides and Ericabatrachus) lineages. Because of the considerable molecular divergence, and external morphology of the single West African torrent-frog species a new genus was erected ( Odontobatrachus). In this study we aim to clarify the systematic position of West African torrent-frogs ( Odontobatrachus). We determine the relationships of torrent-frogs using a multi-locus, nuclear and mitochondrial, dataset and include genera of all African and Asian ranoid families. Using micro-tomographic scanning we examine osteology and external morphological features of West African torrent-frogs to compare them with other ranoids.

Results

Our analyses reveal Petropedetidae ( Arthroleptides, Ericabatrachus, Petropedetes) as the sister taxon of the Pyxicephalidae. The phylogenetic position of Odontobatrachus is clearly outside Petropedetidae, and not closely related to any other ranoid family. According to our time-tree estimation Odontobatrachus has been separated from other frog lineages since the Cretaceous (90.1 Ma; confidence interval: 84.2-97.1 Ma). Along with this molecular evidence, osteological and external diagnostic characters recognize West African torrent-frogs as distinct from other ranoids and provide strong support for the necessity of the recognition of a new family of frogs. This is the only endemic vertebrate family occurring in the Upper Guinea biodiversity hotspot.

Conclusion

Based on molecular and morphological distinctiveness, the West African torrent-frog Odontobatrachus natator is allocated to a newly described anuran family . The discovery of an endemic vertebrate family in West Africa highlights the Upper Guinean forests as an outstanding, but highly endangered biodiversity hotspot.