Coexistence of European hares and Alpine mountain hares in the Alps: what drives the occurrence and frequency of their hybrids?

AbstractAs a glacial relict species, mountain hares are adapted to cold and snowy conditions. Conversely, European hares originate from the grasslands of the Middle East and spread from there throughout low‐lying agricultural areas of Europe. Mountain hares and European hares generally occur allopatrically, however, sympatry occurs in some areas. In sympatric areas, introgressive hybridisation poses a threat to the Alpine mountain hare by reducing its genetic integrity. Introgressed individuals can be found in both species but are far more frequent in European hares than in mountain hares. The ecology of hybrids is poorly known in these species. To examine the Alpine mountain hare and European hare populations in the Alps with a particular focus on the occurrence and ecology of their hybrids, we performed molecular genetic analysis of hare faecal samples collected in four study areas in the Alps in South Tyrol for three winters and compared habitat associations of the genotyped samples. We recorded 150 individuals (i.e. 14 hybrids, 25 European hares and 111 Alpine mountain hares). Four introgressed individuals were at levels consistent with F2 hybrids, whereas the others showed an older interspecific gene flow. We found that hybrid faeces tended to be at lower elevations compared to those of Alpine mountain hare but at higher elevations than those of the European hare. The frequency of Alpine mountain hares decreased as the proportion of Alpine grassland increased but was positively correlated with the proportion of dwarf shrub heaths. No effect of vegetation type was found for the frequency of European hares and hybrids. Our results support the widely raised concerns that the European hare, as a generalist, is a strong competitor with the Alpine mountain hare in the Alpine ecosystem in the time of global climate change.