Data from: Regulation of thermal acclimation varies between generations of the short-lived mosquitofish (Gambusia holbrooki) that developed in different environmental conditions

1. Environmental variability and perturbations can influence population
persistence. It is therefore important to understand whether and how
animals can compensate for environmental variability, and thereby increase
resilience of natural populations. Evolutionary theory predicts that in
fluctuating environments selection should favour developmental modifiers
that reduce phenotypic expression of genetic variation. The expected
result is that phenotypes are buffered from environmental variation across
generations. 2. Our aim was to determine whether phenotypes of
mosquitofish (Gambusia holbrooki) remain stable across generations in
which individuals were born into different thermal environments. We
predicted that the spring generation (cool environment) would acclimate by
increasing the concentration of regulatory transcription factor mRNA and
activities of rate-limiting enzymes (hierarchical regulation) to
compensate for the negative thermodynamic effects of lower temperatures on
metabolic and locomotor performance. In contrast, the summer-born
generation (warm environment) would show less capacity for acclimation and
hierarchical regulation. 4. We show that fish from both generations
acclimated, but that there were significant differences in the phenotypic
consequences of acclimation. The overall result was that sprint
performance, metabolic scope, and the activities of cyctochrome c oxidase
and lactate dehydrogenase were buffered from environmental change, and did
not differ between spring and summer fish at their natural water
temperatures of 15oC and 25oC, respectively. However, there were
differences between generations in sustained swimming performance and
citrate synthase activity. 5. We used metabolic control analysis to show
that modes of regulation of metabolic scope and locomotor performance
differed between generations. Spring fish showed primarily hierarchical
regulation, but regulation in summer fish relied to a lesser extent on
rate-limiting enzymes and transcription factors. 6. We suggest that
developmental modifiers are favoured in fluctuating environments to
maximise phenotypic fitness of each generation. We show that the
interaction between developmental and reversible acclimation can render
physiological performance of a natural population independent from climate
variation.