Range dynamics driven by Quaternary climate oscillations explain the distribution of introgressed mtDNA of Lepus timidus origin in hares from the Iberian Peninsula

Aim: A striking case of mitochondrial DNA (mtDNA) introgression occurs in the Iberian Peninsula: the mtDNA of Lepus timidus, a species that inhabited this territory during the Last Glacial Maximum (LGM), is almost fixed in the Iberian range of Lepus europaeus, is very frequent in the northern half of Iberia within Lepus granatensis, and is fixed in Lepus castroviejoi. Here, we used a transdisciplinary approach to understand the ecological drivers of the distribution of this introgressed mtDNA in the Iberian hare species. Location: Europe, with an emphasis on the Iberian Peninsula. Methods: First, we modelled the climatic niche of L. timidus to predict the favourability for the species during the LGM. Second, we gathered data regarding L. timidus mtDNA introgression for 1137 individuals (139 populations) from the Iberian Peninsula. We tested whether the climatic favourability for L. timidus during the LGM reflects the frequency of the introgressed mtDNA in the carrier hare populations. Results: The climatic favourability for the LGM is positively related to the presence of individuals with L. timidus mtDNA, and discriminates better than by chance between individuals with and without this lineage. At the population level, the favourability values relate to the observed frequencies of mtDNA introgression and discriminate between populations with and without L. timidus mtDNA. Main conclusions: The results suggest that the geographical distribution of L. timidus mtDNA introgression is linked to L. timidus distribution in Iberia during the LGM. Our study helps to improve our understanding of the role of climate in the reticulated evolutionary history of hares, and is a first step towards understanding the ecological impact of mtDNA introgression on Iberian hares.