Dispersal under duress: Can stress enhance the performance of a passively dispersed species?

Passively dispersed organisms do not expend energy during movement; this lack of agency suggests that the distance dispersed by these species is predominantly affected by extrinsic abiotic factors. However, theory predicts that greater dispersal has ecological and evolutionary advantages under some circumstances (e.g., stressful environments). If the biological traits that underlie passive dispersal respond phenotypically to environmental cues, these species may be able to maintain or improve dispersal distance in response to local stressors. We empirically examined context-dependent dispersal, and verified the hypothesis that the traits of an invasive, wind-dispersed plant species plastically affect predicted dispersal distances under drought conditions. We found that the effect is strongest among tall individuals that are most likely to contribute to spread, and that dispersal trait covariation among taller stressed individuals matches expectations from a fluid dynamical model. These responses probably contribute to this species' success as a fugitive invader in complex landscapes.