Abstract
As environments are multifaceted, organisms’ fitness should be maximized if they integrate their dispersal decisions across as many environmental dimensions impacting their fitness as possible. However, to what extent individuals effectively use multiple environmental cues according to their fitness impact, and if so, whether cues have additive, synergistic or antagonistic effects on dispersal, is still poorly understood. In this experimental study, we quantified the combined effects of temperature, salinity and resource changes on dispersal decisions of the ciliate Tetrahymena thermophila, and tested whether they depend on the fitness consequences of these environmental changes. Environmental changes had non-additive effects on both fitness and dispersal, and dispersal plasticity was positively correlated with fitness sensitivity no matter the number of stressors. Environmental conditions that decreased fitness also tended to decrease dispersal propensity. Rather than a simple maladaptive scenario, we propose several hypotheses that could account for this surprising result.