The maintenance of variation in avian personality: the role of the social environment

PhD ceremony: Ms. E. Fuciková, 13.15 uur, Academiegebouw, Broerstraat 5, Groningen

Title: The maintenance of variation in avian personality: the role of the social environment

Promotor(s): prof. M.E. Visser

Faculty: Mathematics and Natural Sciences

The decrease in biodiversity is a global problem. This loss is often caused by a lack of variation within species in the ability to cope with environmental changes. I tested how selection on and the maintenance of variation in great tit (Parus major) personality depends on the phenotypes present in the social environment. I thereby focussed on negative frequency-dependent selection (nFDS), in which the rarer phenotype has the highest fitness. Yearly fitness was studied by investigating adult survival, reproductive success (number of juveniles a breeding pair produced that recruited) and juvenile survival. In the analyses of the long-term data I show an impact of the personality phenotypes in the social environment on adult survival if own personality is included, on reproductive success independent of parents personality, but not on juvenile survival. Years differed in type and in direction of selection and nFDS acted on personality via adult survival only in one year. A field experiment confirmed these results: selection differed between the sexes in adult survival but was not detected in reproductive success. Therefore, I propose that social and non-social environmental heterogeneity triggers variation in and the direction of selection on personality. Interactions of different selection mechanisms together with age and sex differences contribute to the maintenance of variation in personalities. Hence, evolutionary processes depend on variation and fluctuations in local conditions in which the composition of the social environment is an important factor. Finally, I stress the importance of variation in local social and non-social conditions for species conservation.