Does Early-Life Food Shortage Alter Female Life History at Elevated Temperatures?

AbstractGlobal warming is reducing food availability in many aquatic systems, raising questions about the combined effects of higher temperatures and lower food availability on fish life histories. 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 investigated how water temperature (24°C or 28°C) and early-life food availability (control or restricted) affected adult life history traits in female guppies (Poecilia reticulata). There was no significant interaction between temperature and food availability affecting adult traits, nor was there an independent effect of food availability. Instead, higher temperature alone affected female life histories. Females at 28°C were larger in early adulthood but then grew more slowly and produced fewer, smaller offspring than females at 24°C. The effect of temperature on reproduction persisted after controlling for female size, suggesting a shift in the fecundity-female size relationship. Adult mortality was greater at 28°C. Higher temperatures also resulted in a longer gut but did not affect immunity or telomere length of the surviving females. Our results suggest that tropical fish may be vulnerable to increased temperatures but resilient to brief periods of early-life food limitation.