Haplotype diversity of mountain hare mtDNA among native mountain hares and introduced brown hares in Scandinavia

Natural hybridisation and subsequent introgression mediate the transmission of mitochondrial DNA (mtDNA) from native mountain hares (Lepus timidus) to introduced brown hares (L. europaeus). We investigated mtDNA Restriction Fragment Length Polymorphism among 62 Scandinavian mountain hares, 20 brown hares with mountain hare mtDNA and 19 presumed hybrids from 57 localities in Sweden and Norway. A high level of mtDNA haplotype diversity was detected (0.90 ± 0.026). Mountain hare mtDNA haplotypes transferred to brown hares were different from those among mountain hares, both sympatric and allopatric (p < 0.05). One possible explanation is that hybridisation and introgression were more common during the initial phase of contact between the species following the introduction of brown hares, after which some haplotypes have become extinct in declining mountain hare populations, but have been preserved among the brown hares with mountain hare mtDNA.