Phylogenetic position of a monotypic Ethiopian endemic rodent genus Megadendromus (Rodentia, Nesomyidae)

摘要

The taxonomic and phylogenetic position of the Nikolaus's African climbing mouse (Megadendromus nikolausi), formerly known only from four specimens, remained for a long time ambiguous. Here, we report, for the first time, the phylogenetic analysis of this species using mitochondrial (cytochrome b) and nuclear (interphotoreceptor binding protein) gene sequences obtained from a new specimen recently caught in the Bale Mountains in south-eastern Ethiopia. Our analyses strongly suggest that the Nikolaus's climbing mouse does not belong to a distinct monotypic genus, but to the genus Dendromus. The first karyotype description of this enigmatic Ethiopian endemic is presented. The diploid set comprises 18 pairs of bi-armed chromosomes, 2N = 36, one of the lowest diploid numbers reported for the genus Dendromus (2N = 30-52). Moreover, the phylogenetic analysis reveals that another very distinctive Ethiopian endemic, Dendromus lovati, sometimes placed in a subgenus Chortomys, occupies an internal position within Dendromus s.s. The results suggest that the Ethiopian Plateau is an important center of high diversity and adaptive radiation for the genus Dendromus. The conservation status of M. nikolausi is assessed.