The hydroperiod gradient drives species sorting in pace-of-life strategies but not in stressor sensitivity in Lestes damselfly larvae.

Many species sort along environmental gradients, whereby species traits are predicted to shift as integrated sets of life-history, behavioural and physiological traits thereby making up a fast-to-slow pace-of-life continuum. This has also been predicted to cause species differences in stressor sensitivity along such gradients with a faster pace-of-life causing a higher sensitivity. We tested for predictable differences in pace-of-life and in stressor sensitivity for a set of four Lestes damselfly species that separate along the hydroperiod gradient. We reared in a common-garden experiment, larvae of two vernal pond specialists, L. dryas and L. barbarus, and two hydroperiod generalists, L. sponsa and L. virens, and exposed them to transient food deprivation and pesticide exposure, and monitored a set of life-history, behavioural and physiological traits both in the larvae and in the adults. Consistent with the time constraints imposed by the shorter hydroperiod of their habitat, the vernal pond specialists showed a faster pace-of-life (faster growth and development, and higher activity levels) than the hydroperiod generalists. Yet, in contrast with theory, this was not associated with a higher metabolic rate and a lower energy budget, neither with a higher oxidative damage to lipids. Both food deprivation and pesticide exposure were experienced as stressors, and species showed compensatory responses to cope with the transient food deprivation, including compensatory growth and delayed development. Nevertheless, the sensitivity to these stressors could not be predicted based on the difference in pace-of-life strategy between the vernal pond specialists and the hydroperiod generalists because of a decoupling of life-history and physiological traits. Our study indicates that while pace-of-life strategies change largely predictably along the hydroperiod gradient, these are not reliable predictors of species sensitivity to stressors. This highlights the need to consider also physiological traits to arrive at a generalizable predictive framework of species sensitivity to global change.