The Ethiopian highlands are the most extensive complex of mountainous habitats in Africa. The presence of the Great Rift Valley and the striking elevational ecological gradients inhabited by recently radiated Ethiopian endemics, provide a wide spectrum of model situations for evolutionary studies. The extant species of endemic rodents, often markedly phenotypically differentiated, are expected to possess complex genetic features which evolved as a consequence of the interplay between geomorphology and past climatic changes.
An international team of researchers, whose member was Radim Šumbera from the Department of Zoology, Faculty of Science, studied the evolution of Stenocephalemys rats in the Etiopian Highlands. The team used genetic database of these rats, consisting of 347 specimens from four about 40 localities. Using this database, they assessed the relative importance of natural selection, geographical isolation and crossing for the emergence of new species during the Pleistocene period.
Phylogenetic analysis, together with the geographic distribution of the genetic structure, suggests a complex reticulate evolution. The evolution of Stenocephalemys rats involved allopatric speciation, two cases of disruptive selection along the elevational ecological gradient, multiple crosses of the Great Rift Valley in dry and cold periods of the Pleistocene, followed by hybridization and introgression mitochondrial DNA on imperfect reproductive barriers. Comparison of this genetic structure to other Ethiopian endemic taxa highlight the geographical areas of special conservation concern, where biodiversity studies should be carried out to prevent endemic taxa from going extinct even before they are recognized.
Bryja, J., Kostin, D., Meheretu, Y., Šumbera, R., Bryjová, A., Kasso, M., … & Lavrenchenko, L. A. (2017). Reticulate Pleistocene evolution of Ethiopian rodent genus along remarkable altitudinal gradient. Molecular Phylogenetics and Evolution.