Evidence for climate-mediated range expansion of hybrid wood ants

Abstract Climate change challenges many species. To persist, species can shift ranges, respond plastically, and adapt. Yet, these responses require variation - often limited in natural populations. While hybridisation can quickly increase genetic variation, potentially facilitating climate adaptation, it is unclear how hybrids respond to climatic changes. Here, we combine whole-genome, life-history, and climatic data of 67 wood ant populations across Finland to assess whether F. aquilonia x F. polyctena hybrids have advantages in warming climates compared to their cold-adapted parent F. aquilonia. We found that hybrids are active and their offspring emerge earlier in spring, suggesting a competitive advantage over F. aquilonia. Hybrids also withstand acute temperatures relevant in nature better than F. aquilonia. Further, the hybrids’ border has shifted 200 km northwards, coinciding with the expansion of climatic conditions suitable for hybrids. Our results provide compelling evidence that hybrids perform better under warming climates than their cold-adapted parent, and that recent climatic changes can lead to range expansion of hybrids.