Integrative taxonomic revision of the Ethiopian endemic rodent genus Stenocephalemys (Muridae: Murinae: Praomyini) with the description of two new species

Abstract

Ethiopian rats (genus Stenocephalemys) represent a monophyletic group of Ethiopian endemic rodents that diverged in the Ethiopian Highlands during the Pleistocene. Because of the frequent occurrence of so-called reticulate evolution (i.e. repeated hybridization of partially diverged populations), their taxonomy has not been adequately resolved, despite the fact that they belong to the most abundant rodent genus in Ethiopia and are important as pests and carriers of pathogens (e.g. hantaviruses). Here we analysed material for 623 Stenocephalemys specimens using integrative taxonomy composed of genomic analyses (388 nuclear markers and complete mitogenomes), 2D-geometric morphometry of skulls and classical morphometry of external traits. The genus consists of six clearly defined gene pools (= species), characterized by specific morphology, ecology and distribution. Two of them, described here as new species, live in fragmented populations in Afroalpine habitats in the north-western part of the Ethiopian Highlands. We also showed that mitochondrial DNA is not applicable as a universal diagnostic tool for species discrimination in Stenocephalemys, because of multiple cases of mitochondrial introgression. This finding illustrates the utility of the genus as a suitable model for future studies of mito-nuclear coevolution along an elevational gradient.