Taxonomic revision of the genus Asellia (Chiroptera: Hipposideridae) with a description of a new species from southern Arabia

Two species are currently recognised within the genus Asellia, a typical inhabitant of arid areas of northern Africa and south-western Asia. Most of the distribution range of the genus is covered by Asellia tridens, while the other species, A. patrizii, is restricted to Ethiopia, Eritrea and several Red Sea islands. We analysed the morphological variation in an extensive set of Asellia samples covering the range of the genus, including most of the available type material. In a representative subset of samples, we employed molecular genetic analysis to infer the phylogenetic relationships within the broadly distributed A. tridens. Morphological comparisons revealed four distinct morphotypes. Except for the endemic A. patrizii, almost all African Asellia were found to belong to the same morphotype as most of the Middle Eastern specimens. This morphotype was unambiguously identified as A. tridens. Two other morphotypes of tentative A. tridens were further recognised based on skull shape differences; one in the southern Arabian region of Dhofar, the other in Socotra and Somalia. Phylogenetic analysis of complete sequences of the mitochondrial cytochrome b gene yielded three main monophyletic groups, which corresponded to the morphotypes revealed for A. tridens. Significant genetic divergences reaching over 5% and 12%, respectively, were discovered between them. Based on the morphological and molecular data obtained, we propose a split of the current A. tridens into three separate species: A. tridens in northern Africa and most of the Middle East, A. italosomalica in Socotra and Somalia, and Asellia sp. nov. in southern Arabia. Molecular dating, along with the available paleontological information and geological history of the Arabian Peninsula, supports an Arabian origin of the contemporary Asellia. While profound divergence of the Socotran form may be linked to the split of Socotra from the southern Arabian coast in the Middle Miocene, the low sequence variation of Asellia in most of Africa and the Middle East suggests a relatively recent colonisation of this vast area during the Pleistocene. The newly described form from southern Arabia most likely represents a relic of aridisation during the Miocene-Pliocene transition.