Warming and biotic interactions shape selection on plant traits and their plasticity

Global warming will impact natural selection on plant traits and their plasticity by influencing phenotypes, biotic interactions, and fitness. Because warming affects biotic interactions, community composition may influence how warming affects selection on plants, but this is little studied. We grew full-sibling pairs of Brassica rapa plants in an ambient and hot temperature environment and exposed them to visitation by a pollinator (Bombus terrestris), a pollinating herbivore (Pieris rapae), or their combination. We recorded plant phenotypes, insect visitation, herbivory, and plant fitness. We used these to calculated phenotypic selection on plant traits and their plasticity, including additive and nonadditive effects. Elevated temperature changed selection on traits related to pollinator attraction, such as flower number, nectar production, and floral scent emission. We found both positive and negative selection on temperature-mediated trait plasticity depending on the biotic treatment. Elevated temperature changed patterns of additive and non-additive selection on a variety of traits including flower morphology and scent. This study shows that elevated temperatures can reshape patterns of phenotypic selection, including nonadditive effects, and plastic trait expression. Effects of elevated temperature on phenotypic selection depended on the biotic interactors, highlighting the importance of community context for the effects of warming on natural selection.