Thermal tolerance in two wood ant species and their hybrids

Local populations can cope with rising temperatures, if they have adaptive potential to face the new thermal regime. Hybridization with a closely related lineage is one potential source of adaptive genetic variability and an outstanding question is whether hybridization could help contemporary populations to adapt in the face of current environmental change. We investigate thermal adaptation by testing for differences in cold and heat tolerances between Finnish populations of two mound-building wood ants, Formica polyctena and Formica aquilonia, and their naturally occurring hybrids. The results showed that parental individuals differed in both cold and heat tolerances and expressed thermal limits which reflect the global distributions of the parental species, in support to the thermal adaptation hypothesis. However, hybrids could not combine the thermal tolerance of both parental species as they were equally heat-tolerant to F. polyctena, but not equally cold-tolerant to F. aquilonia. ...