Box 1 Sources of phenotypic variation in human-altered environmentsTrait values differ as a result of the environment, as a result of evolved genetic differences, or both. Both environmental and genetic variation can lead to phenotypic changes that are adaptive (or not) in human-altered environments. † shows the influence of such variation on the probability of population persistence (‘+’ positive, ‘–’ negative). Developmental flexibility and behavioural plasticity may enhance the performance of individuals in changed circumstances. For example, threatened prey species may learn to avoid introduced predators by associating novel signals with the threat (‡).
[ Fates of populations via individual and evolutionary responses to environmental change. Adaptive responses that increase the probability of population persistence may be induced or genetically based; they may also operate simultaneously, and plasticity may evolve as well (e.g. §; ¶). Adaptive change is not guaranteed (‖; ††). ]