Forest monkeys and Pleistocene refugia: a phylogeographic window onto the disjunct distribution of theChlorocebus lhoestispecies group

Abstract

The reconstruction of evolutionary relationships among a group of closely-related taxa provides a valuable window onto their biogeographic history. This is the first such molecular phylogenetic study to survey all three taxa of the Chlorocebus lhoesti species group, a group of Old World monkeys that includes C. lhoesti, Chlorocebus preussi, and Chlorocebus solatus. Representatives of each species were surveyed for two Y-chromosomal genes, TSPY (∼2240 bp) and SRY (∼780 bp), and one X-chromosomal intergenic region (∼9300 bp) homologous to a portion of human Xq13.3. Maximum likelihood topologies inferred from these sequences confirm that the lhoesti group is monophyletic within the tribe Cercopithecini, as suggested by earlier karyotype studies. Within this group, C. lhoesti (Albertine region) and C. preussi (Cameroon, Nigeria, Bioko) cluster to the exclusion of C. solatus (Gabon). This phylogeographic pattern, evaluated in the context of Pleistocene glacial cycles and lhoesti group ecology, suggests: (1) the common ancestor of the group probably arose in west central Africa, (2) dispersal to the Albertine region is likely to have occurred during a glacial maximum, rather than an interglacial pluvial, and (3) this dispersal probably occurred via a path north of the Congo Basin. Divergence date calculations suggest C. solatus separated from the ancestral stock at ∼2.1 Ma, whereas C. preussi and C. lhoesti bifurcated later, at ∼0.5 Ma. Taken together, these evolutionary analyses draw attention to one period in the Pleistocene (∼0.5 MYA) when a dispersal corridor suitable to montane taxa is likely to have connected the highlands of east central and west central Africa. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154, 408–418.