The evolutionary significance of intra- and intercolonial variation in behavior, morphology, genetics and immuno-competence in ants

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Variation and heritability of traits connected to differential reproduction invariably leads to natural selection and hence to evolution. Yet, for many species the direction and strength of natural selection on specific traits is largely unknown. We will investigate which traits of Temnothorax ants are under selection in the field by estimating selection gradients on traits such as ant behavior (standardized tests of aggression, explorative, social behaviors), worker body size, heterozygosity, genetic diversity and immune-competence via trait-fitness regressions. In social insects, not only mean trait values can vary between independent evolutionary units – the colonies – but also variation in traits. Division of labor has been recognized as a primary cause for the ecological success of insect societies and we will test how behavioral, genetic, immunological and morphological variation among nest mates is associated with colony productivity. If a strong division of labor is adaptive, then ant colonies with stronger variation in behavior will be more productive. Preliminary studies demonstrate that colonies consistently vary in morphology and behavior and that within-colony behavioral variation is associated with a fitness correlate – per-capita-productivity. However, we could also show environmental influences on ant behavior, e.g. aggression of ant colonies increased with local nest density and social parasite contact. We therefore aim to identify how natural selection (acting on genes underlying behavior) and behavioral plasticity (a response to ecological conditions) influence ant behavior.