Is a valid endemic Ethiopian taxon?

Black-and-white colobus ( Rüppell, 1835) are arboreal Old World monkeys inhabiting large parts of the deciduous and evergreen forests of sub-Saharan Africa. Two of the eight subspecies of are endemic to Ethiopia: and . However, the validity of the Ethiopian taxa is debated and observed morphological differences were attributed to clinal variation within . To date, no molecular phylogeny of the Ethiopian guerezas is available to facilitate their taxonomic classification. We used mitochondrial DNA markers from 94 samples collected across Ethiopia to reconstruct a phylogeny of respective mitochondrial lineages. In our phylogenetic reconstruction, augmented by orthologous sequence information of non-Ethiopian black-and-white colobus from GenBank, we found two major Ethiopian mitochondrial clades, with one being largely congruent with the distribution of . The second clade was found only at two locations in the eastern part of the putative range of . This second lineage clustered with the lowland form, , from central Africa, whereas the lineages clustered with and from Kenya and northern Tanzania. These two guereza lineages diverged around 0.7 million years ago. In addition, mitochondrial sequence information does not support unequivocally a distinction of and . Our findings indicate a previous biogeographic connection between the ranges of and and a possible secondary invasion of Ethiopia by members of the -- clade. Given these phylogenetic relationships, our study supports the two-taxa hypothesis, making an Ethiopian endemic, and, in combination with the taxon's very restricted range, makes it one of the most endangered subspecies of black-and-white colobus.