Genomic diversity, evolutionary history, and species limits of the endemic Ethiopian laminate-toothed rats (genus Otomys, Rodentia: Muridae)

The Ethiopian Highlands represent one of the most important centres of endemism on Earth. Six endemic species of laminate-toothed rats have been reported from Ethiopia in a previous study based mostly on morphological analyses. Largely missing genetic data for some of the species, insufficient sampling across Ethiopia, and presence of a pseudogene on cytochrome b created knowledge gaps in basic taxonomy, distribution, and phylogenetic position of the Ethiopian taxa. Here we perform an integrative taxonomic revision of the group by using the largest available sets of genomic and morphological data. We first reconstructed the mitochondrial phylogeny of the whole genus, delimited major clades, and evidenced two independent colonization events of Otomys to Ethiopia. By using genome-scale SNPs, we delimited putative Ethiopian species and analysed their phylogenetic relationships. In genetically characterized specimens we assessed morphological variation of skulls. We confirmed the presence of six previously reported species and significantly extended the known distributional range for some of them. Furthermore, we discovered a genetically and morphologically distinct lineage in northern Ethiopia, probably representing a new species. The speciation processes are similar to other Afromontane Ethiopian endemic rodent clades, with prevailing allopatric diversification combined with reticulate processes.