Differences in thermal tolerance between parental species could fuel thermal adaptation in hybrid wood ants

Genetic variability is essential for adaptation and could be acquired via hybridization with a closely related lineage. We use ants to investigate thermal adaptation and the link between temperature and genetic variation arising from hybridization. We test for differences in cold and heat tolerance between Finnish Formica polyctena and Formica aquilonia wood ants and their naturally occurring hybrids. Using workers, we find the parental individuals differ in both cold and heat tolerances and express thermal limits which reflect their global distributions. Hybrids however cannot combine thermal tolerance of parental species as they are equally heat-tolerant to F. polyctena , but not equally cold-tolerant to F. aquilonia . We then focus on a single hybrid population to investigate the relationship between temperature variation and genetic variation across 16 years using reproductive individuals. Based on the thermal tolerance results, we expected the frequency of
putative F. pol...