The strange blood: natural hybridization in primates

Hybridization between two closely related species is a natural evolutionary process that results in an admixture of previously isolated gene pools. The exchange of genes between species may accelerate adaptation and lead to the formation of new lineages. Hybridization can be regarded as one important evolutionary mechanism driving speciation processes. Although recent studies have highlighted the taxonomic breadth of natural hybridization in the primate order, information about primate hybridization is still limited compared to that about the hybridization of fish, birds, or other mammals. In primates, hybridization has occurred mainly between subspecies and species, but has also been detected between genera and even in the human lineage. Here we provide an overview of cases of natural hybridization in all major primate radiations. Our review emphasizes a phylogenetic approach. We use the data presented to discuss the impact of hybridization on taxonomy and conservation.