Molecular variation and chromosomal stability within Gerbillus nanus (Rodentia, Gerbillinae): Taxonomic and biogeographic implications

The systematics of the rodent genus Gerbillus still needs clarifications. Within this genus, Gerbillus nanus is a species often considered to have a wide geographic distribution ranging from northwest India to the Mauritanian coast. Some authors, however, have suggested that other species, namely Gerbillus amoenus and/or Gerbillus garamantis, may replace G. nanus over a part of, or over the whole of its African area of occurrence. Here, we bring together new karyological data and molecular analyses of cytochrome b mitochondrial gene sequences of G. nanus specimens from various parts of the alleged extended distribution of the species: Pakistan and Israel in Asia, and Libya, Mali, and Mauritania in Africa. The karyotypes of Asian and African specimens appear similar, while a rather important genetic distance was found between samples of specimens from the two continents. This last finding suggests that at least two distinct species exist, G. nanus being the species of Asian distribution, and G. garamantis and/or G. amoenus being the one(s) with African distribution(s). Similar comparative analyses on larger samples are now needed to determine the precise taxonomic situation in this group, as well as the distribution limits of each species.