Hybridization with mountain hares increases the functional allelic repertoire in brown hares

Abstract Brown hares ( Lepus europaeus Pallas) are able to hybridize with mountain L. timidus Linnaeus) and produce fertile offspring, which results in cross-species gene flow. However, not much is known about the functional significance of this genetic introgression. Using targeted sequencing candidate loci combined mtDNA genotyping, we found ancestral diversity Finnish brown hare be small, likely due founder effect range expansion, while flow from constitutes an important source variability. Some variability, such as alleles thermogenin (uncoupling protein 1, UCP1 ), might have adaptive advantage for hares, whereas immunity-related MHC reciprocally exchanged maintained via balancing selection. Our study offers a rare example where expanding species can increase its allelic variability through hybridization congeneric native species, offering route shortcut evolutionary adaptation local environmental conditions.