Evidence for climate-mediated range expansion of hybrid wood ants.

Climate change challenges many species. To persist, species can shift ranges, respond plastically, and adapt, which all require variation. Hybridization can quickly increase genetic variation, potentially facilitating climate adaptation; however, it is unclear how hybrids respond to climatic changes. Here, we combine whole-genome, life-history, acute heat-shock, and climatic data of 69 wood ant populations across Finland to assess whether F. aquilonia × F. polyctena hybrids outperform their cold-adapted parent F. aquilonia in warming climates. Compared to F. aquilonia, hybrids are active and their offspring emerge earlier in spring, and they withstand acute temperatures relevant in nature better. Further, the hybrids' border has shifted 200 km northwards, coinciding with the expansion of climatic conditions suitable for hybrids. Our results provide evidence that hybrids have an adaptive advantage over F. aquilonia due to their admixed ancestry, and recent climatic changes can lead to range expansion of hybrids.