Genetic and morphometric analyses of historical type specimens clarify the taxonomy of the Ethiopian Leptopelis gramineus species complex (Anura, Arthroleptidae)

Frogs of the genus Leptopelis have diversified in the Ethiopian Highlands to occupy forests and montane grasslands both east and west of the Great Rift Valley. Genetic studies revealed that the endemic species Leptopelis gramineus (Boulenger, 1898) comprises multiple unnamed taxa. A careful examination of historical type specimens is, however, needed to fully resolve the taxonomy of the group. Here we use mitochondrial DNA and morphological analyses on a large sample of recently-collected Ethiopian Leptopelis, as well as century-old type specimens to demonstrate that the recently resurrected L. montanus Tiutenko & Zinenko, 2021 (previously Pseudocassina ocellata Ahl, 1924) is a junior synonym of L. rugosus (Ahl, 1924) and corresponds to the taxon found west of the Great Rift Valley, not east as previously thought. Our results show that populations inhabiting the mountains and plateaus east of the Rift constitute a distinct and undescribed species. We provide a re-description of L. rugosus and describe two new species inhabiting the Highlands east of the Great Rift Valley. We provide an identification key, as well as a description of the calls of the members of the Leptopelis gramineus species complex.