Individual variation and selection for phenotypic plasticity of laying date and clutch size across different environmental conditions in Tree swallow (Tachycineta bicolor)

Several studies have emphasized that phenotypic plasticity should be a key mechanism to cope with current rapid environmental changes by allowing individuals to quickly express new adaptive phenotypes. Yet, few studies have investigated the evolutionary potential of plasticity for multiple traits simultaneously and using several different environmental variables. Here, we assess the extent of variation in, and the selection acting on phenotypic plasticity of key ecological traits, laying date and clutch size, using five environmental variables, in a Tree swallow (Tachycineta bicolor) population monitored since 2004. While we found some variation among females in their mean laying date and plasticity, we found evidence of selection acting only on mean laying date. We found no variation among females in mean clutch size or plasticity, such that we could not assess selection acting on either. Our results suggest that the evolutionary potential of plasticity in the population under study is limited, especially for clutch size. More studies investigating plasticity in wild populations and incorporating multiple traits and environmental variables are needed to understand future responses of animal populations to environmental changes.