High evolutionary and taxonomic diversity of gerbils (Gerbillus) in the Horn of Africa

The genus Gerbillus represents an example of the successful Pleistocene radiation among rodents, leading to the emergence of almost 50 currently recognized species inhabiting Asia (from the Middle East to northwest India) and Africa (the Saharo-Sahelian region and eastern Africa). During the last two decades, multiple molecular phylogenetic studies helped to decipher the complex subgeneric structure of this speciose group. However, questions concerning the number of phylogenetic lineages (species) within the genus and their evolutionary relationships remained open, especially because of the lack of genetic material from the Horn of Africa. Here we provide for the first time genetic information on Microdillus peeli (being for more than a hundred years a taxon with an unresolved phylogenetic position) and unequivocally show that it is an internal lineage of Gerbillus. Together with one additional newly characterized lineage of apparently subgenus rank (proposed here as subgenus "Pusillus"), endemic to Somali-Masai region in eastern Africa, these findings document that the Horn of Africa is the center of evolutionary diversity of gerbils in general, and of the genus Gerbillus in particular.