On the phylogenetic history of the Sanje mangabey (Cercocebus sanjei)

Abstract The Sanje mangabey (Cercocebus sanjei) is an Endangered (IUCN) primate endemic to the Udzungwa Mountains, Tanzania. Two populations, both inhabiting montane forest fragments, have been identified. The phylogenetic position of the Sanje mangabey relative to other Cercocebus species remains unclear and this knowledge gap has important conservation implications. Here, we use sequence data from all recognised Cercocebus species to clarify the phylogeny of the Sanje mangabey and estimate its divergence time from other species. Phylogenies were reconstructed using nuclear (CD4 and TSPY) and mitochondrial (COII and control region) sequences. The Sanje mangabey grouped with the Central/East African mangabeys - C. galeritus, C. chrysogaster, and C. agilis – and is estimated to have diverged from the common ancestor shared with these three species 2.34 million years ago (MYA; 95% HPD interval: 1.73–2.95 MYA). The two extant Sanje mangabey populations represent distinct lineages, diverging 0.77 MYA (95% HPD interval: 0.43–1.15 MYA). This divergence and isolation into two montane forest fragments are attributed to: i) increasing aridification in eastern Africa beginning ~ 2.6 MYA, ii) competition with other species, and iii) the formation of physical barriers to dispersal. This study confirms the evolutionary distinctiveness of the Sanje mangabey and therefore conservation management policies should be considered at the species level and the Sanje mangabey populations managed independently as evolutionarily significant units.