PS 35-172 - Assessing the importance of phenotypic plasticity for key ecological traits in a wild bird population

Background/Question/Methods

Evolution and adaptation of populations are, most of the time, slow processes. Facing new selective pressures, a population will evolve over several generations towards phenotypes and genotypes that are favorable to the new environmental conditions. However, in the actual context of accelerated climate change, populations are exposed to new selective pressures over really short period of times, which may challenge their adaptive capacity. This context emphasizes the importance of studying phenotypic plasticity that consists in the expression of different phenotypes from a same genotype, according to the environment. Through phenotypic plasticity a trait can thus be expressed differently without modification of genes, which is an important advantage considering the actual rapid changes of the environment. Here we assess the extent and importance of phenotypic plasticity for key ecological traits, laying date and clutch size, in a Tree swallow (Tachycineta bicolor) population located in southern Québec, which has been monitored since 2004.

Results/Conclusions

Preliminary results suggest that the population mean laying date exhibits limited inter-annual variation, but large intra-annual variation. In our study system, laying dates extend from the Julian day 126 (May 6) to 177 (June 26), a difference of 51 days. These results suggest that females differ in their laying dates adjustment to within-year environmental conditions. Clutch sizes also show limited inter-annual variation, but slight variation is intra-annually, ranging from 2 to 8 eggs. Following these results, we will assess individual phenotypic plasticity in different environmental conditions, such as temperature, occurrence of extreme events and habitat quality, for both laying date and clutch size. We will then evaluate the relationship between phenotypic plasticity and reproductive success to determine if being more plastic confers an adaptive advantage in this population. These analyses will provide information on whether phenotypic plasticity could evolve within this population and inform us on its adaptive potential in face of environmental changes. Our study will contribute to knowledge about the evolutionary potential of phenotypic plasticity in wild populations and improve our understanding of adaptive processes in populations facing changing selection pressures.