Transgenerational effects and acclimation affect dispersal in guppies

Abstract Evolutionary theory predicts that intergenerational environmental fluctuations lead to transgenerational effects where offspring phenotypes are matched to conditions experienced by previous generations. However, in fluctuating environments, transgenerational effects can be detrimental by causing mismatches between ancestral and offspring environments. Acclimation in offspring could alleviate these negative effects. We determined whether the interaction between transgenerational effects and acclimation affects locomotor performance and dispersal in guppies ( Poecilia reticulata ). In a fully factorial experiment, we tested the interaction between ancestral (22 or 30°C for six to eight generations), acclimation (22 or 30°C for 4 weeks) and acute test temperatures (two to five temperatures across 18–34°C). We predicted that matching ancestral and acclimation temperatures to acute environmental temperature maximises physiological capacities (swimming performance [U crit ] and metabolic enzyme activities), and dispersal in an artificial stream. Alternatively, when ancestral and acute temperatures were mismatched, we predicted that thermal acclimation compensates for this mismatch by shifting performance curves. Finally, we hypothesised that physiological capacities are positively related to dispersal. We measured dispersal as a combination of traits characterising the departure and transient phases of dispersal (time taken to leave the introductory pool, voluntary speed against the current, number of dispersal decisions taken) in an 8‐m artificial stream. As hypothesised, U crit was greatest when ancestral, acclimation and acute temperatures matched. Cold acclimation reduced the decrement in U crit resulting from a mismatch between ancestral and acute test temperatures. In both sexes, the interaction between ancestral and acclimation temperatures determined U crit , but not metabolic enzyme activities, and it affected the number of dispersal decisions in males only. Contrary to our hypothesis, physiological capacities did not constrain dispersal. Males were more likely to initiate dispersal when the acute temperatures mismatched their ancestral temperature. After initiating dispersal, males moved at a greater voluntary speed and made more dispersal decisions in environments matching their ancestral environment. Our findings imply that although the interaction between transgenerational effects and acclimation modulates locomotor capacities, these relationships do not necessarily translate to all ecologically relevant locomotor tasks. Instead, sex‐specific life‐history traits such as life span are more likely to influence dispersal, and males in particular may initiate dispersal to escape suboptimal conditions. A plain language summary is available for this article.