Phylogeny of Rungwecebus Figure 2. Phylogenetic position of Rungwecebus in relation to Papio and other members of the Papionini - mitochondrial DNA phylogeny. The phylogram is based on the neighbor-joining algorithm and by applying the TrN+I+G model of sequence evolution. Marked * nodes yielded bootstrap values of $85% (for MP, NJ and ML) or posterior probability values of $0.95 (Bayesian). Red = P. papio, green = P. anubis, grey = P. hamadryas, yellow = P. cynocephalus, brown = P. ursinus. Bars on the right side of the phylogram denote respective baboon clades and are discussed in the text. doi:10.1371/journal.pone.0004859.g002 African papionins into a Cercocebus+Mandrillus and a Lophoce- bus+Theropithecus+Papio+Rungwecebus clade. Among the latter, the clustering of Papio and Rungwecebus was significant. However, due to the low number of polymorphic sites (Table S4) we were unable to resolve the relationships among the five baboon species and whether Rungwecebus is nested within the genus Papio or represents its sister lineage. Only one transversion (guanine present in all Papio species, thymine in all other papionin genera) at position 534 in the TSPY alignment provided some indications that Rungwecebus might be basal. Alternative tree topology tests significantly rejected a sister grouping of Rungwecebus to Theropithecus, Lophocebus or a Cercocebus+Mandrillus clade (P,0.05, P,0.001, Table 1). Although a tree with Rungwecebus as a sister lineage to Papio represents the most likely relationship, an unresolved polytomy including Rungwecebus and the five Papio species was not rejected (P = 0.578, P = 0.604, Table 1). Therefore, a phylogeny with Rungwecebus nested within the Papio clade cannot be excluded. Due to the low number of variable sites in the nuclear data set, divergence ages were estimated only for mitochondrial data. Based on our estimates, the initial split separating southern baboon PLoS ONE | www.plosone.org 3 March 2009 | Volume 4 | Issue 3 | e4859