Selection across scales—merging evolutionary biology and community ecology to understand trait shifts in response to environmental change
Selection acts on traits at both the community level, determining community assembly, and at the population level, determining the outcome of evolution. Selection at both scales combines with phenotypic plasticity to cause shifts in community-level mean trait values (average species trait values weighted by their relative abundance) in response to environmental change. If selection is typically concordant and populations and communities respond in the same direction, then responses to selection within species will amplify shifts in community mean trait values. In contrast, if selection at population and community scales are not correlated or occur in opposite directions, shifts in community mean trait values will be lower than expected based on shifts in species abundances. Plasticity will influence community-level trait values in similar ways: when plastic shifts parallel/oppose selection, community mean trait value changes will be amplified/reduced. The Selection across Scales synthesis group combines the expansive community composition data from LTER experiments with approaches, ideas, and datasets from evolutionary biology to investigate whether plasticity, selection at the population scale, and selection at the community scale are concordant or discordant. The group’s framework and findings will help predict long-term shifts in the community-level mean trait values that determine ecosystem functions.