Mitochondrial phylogeography of the European wild boar: the effect of climate on genetic diversity and spatial lineage sorting across Europe

Abstract

Aim Climate changes in the past had a deep impact on the evolutionary history of many species and left genetic signatures that are often still detectable today. We investigated the geographical pattern of mitochondrial DNA diversity in the European wild boar (Sus scrofa). Our final aims were to clarify the influence of present and past climatic conditions, infer the geographical position of glacial refugia, and suggest post-glacial spatial dynamics. Location Europe. Methods D-loop sequences were obtained for 763 individuals from Portugal to western Russia. Phylogenetic, multivariate and interpolation methods were used to describe the genetic and geographical patterns. Climatic suitability during the Last Glacial Maximum (LGM) was predicted using MaxEnt. The effect of present and past suitability on the observed patterns of diversity was evaluated by multiple linear regression. Results We confirmed the existence of a ubiquitous mitochondrial clade in Europe (E1), an endemic clade in Italy (E2) and a few East Asian haplotypes (A), presumably introgressed from domestic pigs. No Near Eastern haplotypes were detected. Genetic divergence was not simply related to geographical distance. A clear south-north decreasing gradient of diversity was observed, with maximum levels in putative glacial refugia. Latitudinal variation in climatic conditions during the LGM was shown to be a good predictor of current genetic diversity. Moreover, an unexpected similarity between Iberia and eastern Europe was observed, while central European populations showed a higher affinity to the Italian gene pool. Main conclusions The current distribution of mitochondrial genetic diversity was highly influenced by past climatic events, especially those related to the LGM, and is consistent with a major contribution of the Italian peninsula and the Balkans to the post-glacial recolonization of northern areas. More recent processes, such as restocking and extensive hunting, probably acted at rather local scales, without great impact on the global pattern of mitochondrial diversity.