Phylogeography of three closely related African bovids (tribe Alcelaphini)

The phylogeography of three species of African bovids, the hartebeest (Alce laphus buselaphus), the topi (Damaliscus lunatus), and the wildebeest (Conn ochaetes taurinus), is inferred from sequence variation of 345 sequences at the control region (d-loop) of the mtDNA. The three species are closely re lated (tribe Alcelaphini) and share similar habitat requirements. Moreover, their former distribution extended over Africa, as a probable result of th e expansion of open grassland on the continent during the last 2.5 Myr. A c ombination of population genetics (diversity and structure) and intraspecif ic phylogeny (tree topology and relative branch length) methods is used to substantiate scenarios of the species history. Population dynamics are infe rred from the distribution of sequence pairwise differences within populati ons. In the three species, there is a significant structuring of the popula tions, as shown by analysis of molecular variance (AMOVA) pairwise and hier archical differentiation estimations. In the wildebeest, a pattern of colon ization from southern Africa toward east Africa is consistent with the asym metric topology of the gene tree, showing a paraphyletic position of southe rn lineages, as well as their relatively longer branch lengths, and is supp orted by a progressive decline in population nucleotide diversity toward ea st Africa. The phylogenetic pattern found in the topi and the hartebeest di ffers from that of the wildebeest: lineages split into monophyletic clades, and no geographical trend is detected in population diversity. We suggest a scenario where these antelopes, previously with wide pan-African distribu tions, became extinct except in a few refugia. The hartebeest, and probably also the topi, survived in refugia north of the equator, in the east and t he west, respectively, as well as one in the south. The southern refugium f urthermore seems to have been the only place where the wildebeest has survi ved.