Tandem Fusions in Evolution of Ethiopian Endemic Rodents

Abstract

The species number has been strikingly increasing in recent current works on Ethiopian endemic rodents, which to a great extent is due to genomic studies including the karyotype discoveries. Here, the diploid number 2N = 52 is defined anew for the genus Stenocephalemys, endemic to the Ethiopian Highlands, where four karyotypes with 2N values of 54, 50 and 46 were so far described for four taxa. The new karyotype (S. “pseudogriseicauda”) combines into a nearly full series with other 2Ns (except the not yet found 2N = 48) within the genus and shows one interspecific chromosome rearrangement associated with the tandem fusion, in the direction 2N = 54 to 2N = 52. Together with the earlier detection of tandem fusions between karyotypes with 2N = 46 (S. albipes) and 2N = 54 (S. albocaudatus, S. griseicauda), this rodent taxonomic group presents an interesting case for the phenomenon of karyotypic orthoselection in an intrageneric phyletic line via the reoccurence of such characteristic chromosomal rearrangements as tandem fusions.