Context dependence of transgenerational plasticity: the influence of parental temperature depends on offspring environment and sex.

Under environmental change, the relationship between phenotype and fitness can change rapidly, leaving populations vulnerable. Plasticity within and between generations could provide the fastest mitigation to environmental change. However, plasticity may depend on interactions among parental environment, offspring environment and offspring sex, and we know little of how these interactions manifest. We examine the importance of parental and offspring thermal environment in the context of a terrestrial ectotherm (the jacky lizard, Amphibolurus muricatus), where the thermal environment depends on complex thermoregulatory behaviours. By manipulating both parental and offspring thermoregulatory (basking) opportunities in a full factorial design, we found that transgenerational plasticity was highly context dependent. Overall, longer parental thermoregulatory opportunities led to increased growth in offspring, providing a clear fitness benefit to daughters but inducing a cost of increased oxidative stress in sons. Daughters, but not sons, received the greatest advantage when their thermal environment matched that of their parents. The offspring thermal environment had little independent effect on offspring phenotype. Together, the results suggest that both directional selection on offspring size (leading to growth being dependent on thermal conditions) and selection for anticipatory parental effects operate, but with a different balance in males and females. More broadly, restrictions in thermoregulatory opportunities under climatic warming will have negative consequences both within and between generations, but the exact nature will depend on the evolved functional form of plasticity.