Phylogenetic relationships within the Cercocebus-Mandrillus clade as indicated by craniodental morphology: Implications for evolutionary biogeography

Abstract

Objective The African papionin primates commonly known as mangabeys form a diphyletic group with white-eyelid mangabeys (Cercocebus) being most closely related to drills and mandrills (Mandrillus). However, the phylogenetic relationships among members of the Cercocebus-Mandrillus clade have not been investigated in detail, particularly from a morphological perspective. Early studies of white-eyelid mangabeys considered C. agilis to best represent the ancestral lineage and C. torquatus as the most derived species, the result of multiple biogeographic dispersal events. More recently, a sister-clade relationship between Mandrillus and either C. chrysogaster or C. torquatus has been proposed. Materials and Methods Here we present the results of phylogenetic analyses based on 206 craniodental characters (103 representing males and females separately) of four species of Cercocebus and both species of Mandrillus. Results When all species of the Cercocebus-Mandrillus clade are analyzed without molecular constraints, results suggest that C. torquatus may indeed be more closely related to mandrills and drills than to other Cercocebus taxa. However, this topology lacks strong statistical support and may be attributable to incomplete lineage sorting and/or reticulation. When we employ a molecular backbone to constrain Cercocebus and Mandrillus monophyly, C. torquatus appears most basal, while C. agilis and C. chrysogaster form a derived clade. Discussion The molecular backbone view is also congruent with recent genetic analyses and assessments based on the fossil record, but awaits confirmation with additional data. This phylogeny suggests that Cercocebus and Cercocebus-+-Mandrillus arose in western equatorial Africa with subsequent dispersals westward, eastward, and possibly southward over the last >-3 million years.