Phylogeography and population structure of the common warthog (Phacochoerus africanus) inferred from variation in mitochondrial DNA sequences and microsatellite loci

Global climate fluctuated considerably throughout the Pliocene and Pleistocene, influencing the evolutionary history of a wide range of species. Using both mitochondrial sequences and microsatellites, we have investigated the evolutionary consequences of such environmental fluctuation for the patterns of genetic variation in the common warthog, sampled from 24 localities in Africa. In the sample of 181 individuals, 70 mitochondrial DNA haplotypes were identified and an overall nucleotide diversity of 4.0% was observed. The haplotypes cluster in three well-differentiated clades (estimated net sequence divergence of 3.1-6.6%) corresponding to the geographical origins of individuals (i.e. eastern, western and southern African clades). At the microsatellite loci, high polymorphism was observed both in the number of alleles per locus (6-21), and in the gene diversity (in each population 0.59-0.80). Analysis of population differentiation indicates greater subdivision at the mitochondrial loci (FST = 0.85) than at nuclear loci (FST = 0.20), but both mitochondrial and nuclear loci support the existence of the three warthog lineages. We interpret our results in terms of the large-scale climatic fluctuations of the Pleistocene.