Appreciating the Multiple Processes Increasing Individual or Population Fitness

Natural selection results in adaptation for populations, not individuals. Yet environmental change can reduce the expected fitness of an individual. Selection will favor the evolution of traits that allow individuals to proactively compensate for such reduced fitness. Although several well-known processes can achieve this goal, they are still often neglected and often not clearly distinguished. To facilitate greater attention to the full range of processes by which individuals can increase their fitness, we present a classification scheme that integrates these: phenotypic change, selection of the environment, and adjustment of the environment. We outline how these individual-level processes relate to natural selection and population-level fitness. This framework may help to guide research (and teaching) about how individuals and populations may respond to environmental change.