Does early-life food shortage alter the effect of elevated temperature on female life history?

Abstract Global warming is reducing prey availability in many aquatic systems, raising questions about the combined effects of higher temperatures and lower food availability on fish life histories and reproductive output. In ectotherms, higher temperatures accelerate growth and promote an earlier onset of reproduction. However, when fish have less food during development, resource depletion might constrain these temperature-driven processes. We manipulated water temperature (24 or 28°C) and early-life food availability (control or restricted) for female guppies ( Poecilia reticulata ). We measured how both factors affected key life history traits (growth, reproduction, survival, self-maintenance). Higher temperature significantly affected female life histories. Females at 28°C matured at a larger size, but then grew more slowly and produced fewer, smaller offspring than females at 24°C. The effect of temperature on reproduction persisted even after controlling for body size, suggesting there was a shift in the fecundity-size relationship. Adult mortality was greater at 28°C. Higher temperature also resulted in a longer gut, potentially enhancing resource acquisition, but a higher temperature did not affect immunity or telomere length of the surviving females. Early-life food shortage affected very few traits, except for a weak interaction with temperature that affected total fecundity. At 28°C, females that experienced early-life food restriction produced fewer offspring than females with continual food supply. No such diet effect occurred at 24°C. Our results suggest that tropical fish may be severely impacted by increased temperatures (i.e., decreased reproduction with increased morality), but are likely to be resilient to brief periods of food limitations during early development. Interestingly, early-life food shortage caused a reduction in total offspring number but only at 28°C, suggesting that global prey decline might exacerbate the negative effects of a warming climate on stock recruitment of tropical fish.