Genetics, Morphology, Advertisement Calls, and Historical Records Distinguish Six New Polyploid Species of African Clawed Frog (Xenopus, Pipidae) from West and Central Africa.

Ben J Evans,Olivier S G Pauwels,Patrick J Mclaughlin,Richard C Tinsley,Edward L Stanley,Václav Gvoždík,David C Blackburn,Daniel M Portik,Eli Greenbaum,Martha L Tobias,Darcy B Kelley,Timothy F Carter,Gert Jan C Veenstra

doi:10.1371/journal.pone.0142823

Abstract

African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon) to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana) and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups).

Highlights

IntroductionAfrican clawed frogs (genus Xenopus, Pipidae, subfamily Xenopodinae) are found across subSaharan Africa
African clawed frogs are found across subSaharan Africa
Because many species of Xenopus are highly similar in external morphology, we take a multi-faceted approach, first by using molecular phylogenetics to identify distinct lineages and using vocal characteristics, karyotypes, and both external and internal morphology to provide diagnoses for lineages that we recognize as species

Summary

Introduction

African clawed frogs (genus Xenopus, Pipidae, subfamily Xenopodinae) are found across subSaharan Africa. These frogs prefer slow moving or stagnant water as tadpoles and as adults, migration between bodies of water occurs [1]. A consequence of their aquatic way of life is that a suite of morphological features distinguishes them from other anurans These features include a streamlined and flattened body, a vocal organ specialized for underwater sound production, lateral-line organs, claws on the first three (inner) toes, and fully webbed toes. Other species have miniscule distributions, such as that of X. longipes, which occurs exclusively in one lake These frogs have been used as food [3], for human pregnancy tests [4], and as a model organisms for a range of biological investigations [5, 6]. The first amphibian genome to be sequenced was that of X. tropicalis [7] and genome sequencing of X. laevis is underway [8]

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