Browsing by Subject "Formicidae"

Global surface temperature is increasing at an alarming rate. Local populations can cope with the change, 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. My thesis aimed to investigate thermal adaptation by looking into thermal tolerance differences between two mound-building wood ants Formica polyctena and Formica aquilonia and their hybrids. The two parental species have distinct distributions: F. aquilonia can be found in Northern Europe while F. polyctena is distributed from Central Europe to Fennoscandia. The samples for this thesis were collected from a relatively small area in southern Finland and Åland Islands. Aim of my thesis was to clarify whether the two parental species have distinct thermal tolerances, which would reflect the differences in their distributions. I also tested whether hybrid individuals have wider thermal limits since they have alleles from both northern and southern parental species and could therefore show adaptive potential. I tested thermal tolerance differences with two temperature assays: heat-knockdown resistance and chill-coma recovery. I hypothesized that F. aquilonia would express more cold-tolerant thermal limits whereas F. polyctena would express more heat-tolerant limits. My results showed that the parental species differed in their thermal tolerance and expressed thermal limits which reflected their distribution. These results support the thermal adaptation hypothesis: parental species expressed thermal limits that reflected the thermal environment in their native habitat. The results also showed that hybrids could not combine the thermal tolerance of both parental species as they did not have wider thermal tolerance than parental species. Intriguingly, dry weight had a significant role in thermal tolerance, bigger ants coping better with higher temperatures. These results contribute to building up knowledge on the outcomes of hybridization and the potential that species possess in coping with the environmental change. Wood ants are keystone species in boreal forests and the findings of my thesis shed a light on the changes in population dynamics for these species in the face of global climate change.