The role of forest expansion and contraction in species diversification among galagos (Primates: Galagidae)
Here, I investigate galagid diversification and current distribution in the context of major climatic and geological events in sub-Saharan Africa. Given their widespread distribution and presence in a large range of diverse habitats, galagids represent an excellent group to investigate the role of forest contraction and expansion on biological diversification in sub-Saharan Africa.
Sub-Saharan Africa (Afrotropical Region).
I assembled a supermatrix including 53 nuclear loci and three mitochondrial markers for 94% of the galagid species currently recognized. Bayesian and maximum likelihood methods were used to infer phylogenetic relationships and times of divergence within the family. Ancestral ranges were estimated using several methods, including ‘BioGeoBEARS’ and rasp.
Phylogenetic analyses corroborated previous results regarding the evolutionary history of this family: (1) early origin of the family soon after the Eocene-Oligocene boundary; (2) dwarf galagos (Galagoides spp.) represent a polyphyletic group with two well-defined clades, one in central-west Africa and one in the east; and (3) divergences within galagids are relatively old with most genera already present by the Late Miocene. The biogeographical analysis indicates central African origins and subsequent expansion to the east in the Early-Middle Miocene. An expansion to the northern and southern savannas occurred between the Late Pliocene and the Middle Pleistocene.
The results of this study clarify several questions related to the evolutionary history of the Galagidae in the context of sub-Saharan African biogeography. This study suggests that galagid evolution and diversification was affected by three major climatic episodes: (1) the global cooling and forest contraction in the Early Oligocene, (2) the forest expansion and the uplift of the African rifts in the Miocene and (3) the aridification and extension of open woodlands and savannas in the Late Miocene and Plio-Pleistocene.