Pan-African Voyagers: The Phylogeography of Baboons

Abstract

Baboons of the genus Papio have colonised wide areas of Africa and parts of the Arabian Peninsula. Traditionally, 5 phenotypically distinct morphotypes (species) are recognised: chacma baboons, yellow baboons, olive baboons, Guinea baboons and hamadryas baboons. We used mitochondrial DNA ("Brown" region) sequence data obtained mainly from faecal samples collected across the geographical range of baboons to reconstruct their phylogenetic relationships. Eight well-supported major haplogroups were detected, which reflect geographic populations. These disagree with the traditional classification of baboons into only 5 taxa. We found that West African olive and chacma baboons both comprise at least two deeply separated clades. In the case of chacma baboons, they correspond to recognised morphotypes (Cape chacma and grey-footed chacma). Our data also support a previously suggested distinction between yellow and Kinda baboons from central Zambia. Two other terminal clades from eastern Africa comprise either eastern olive and hamadryas baboons or eastern olive and yellow baboons. Southern yellow baboons cluster with grey-footed chacma baboons. Our data also indicate a possible mitochondrial overlap between Guinea baboons and a particular lineage of western olive baboons from Ivory Coast. These results support recent molecular studies, which detected several para-and polyphyletic mitochondrial clades in Papio, suggesting that the evolutionary history of baboons is even more complicated than previously thought. Thus, important roles might have been played by multiple phases of fragmentation, isolation, hybridisation, introgression, and nuclear swamping, hence, reticulation. These processes were most likely triggered by multiple cycles of expansion and retreat of savannah biomes during late Pliocene and Pleistocene glacial and inter-glacial periods. We also speculate on the likely dispersal pathways of these primates that may have led to their current distribution.

Distribution of Mitochondrial Clades and Morphotypes of BaboonsPapiospp. (Primates: Cercopithecidae) in Eastern Africa

“…We confirm the previously assumed boundary between the distributions of southern and northern clades in Tanzania (figure 5; Zinner et al, 2011). This boundary runs from the lower Rufiji River in the east across central Tanzania to the mouth of the Malagarasi River at Lake Tanganyika in the west.…”

“…The general topology of our phylogenetic tree for Papio in eastern Africa is similar to those found in earlier studies (Zinner et al, 2009a(Zinner et al, , 2011Liedigk et al, 2014).…”

“…Like other savanna-living mammals (Lorenzen et al, 2012), baboons were impacted by multiple cycles of expansion and retreat of savanna biomes during Pleistocene glacial and inter-glacial periods, and other climatic changes Trauth et al, 2015). Recurrent fragmentation and reconnection of populations, extinctions, and distribution shifts of demes likely led to multiple phases of isolation, hybridization, and introgression among populations (Zinner et al, 2009a(Zinner et al, , 2011.…”

“…Northern East African baboons, on-the-other-hand, seem to have experienced more introgression due to more frequent reconnection of populations. Here the possible introgression of olive baboons into hamadryas and yellow baboons might be of particular interest (see Zinner et al, 2011 for a more detailed scenario). There is some evidence that ancient introgression occurred even beyond the species level, as found in kipunji Rungwecebus kipunji (Ehardt, Butynski, Jones & Davenport, 2005) (Jones et al, 2005).…”

“…Phylogenetic reconstructions, based on parts or even complete mt-genomes, reveal several mt-haplogroups or clades. These, however, are only marginally concordant with the morphological variation or taxa (Newman et al, 2004;Zinner et al, 2009aZinner et al, , 2011Zinner et al, , 2013. (Kingdon,1971).…”