Ontogenetic reduction in thermal tolerance is not alleviated by earlier developmental acclimation in Rana temporaria

Complex life-histories may promote the evolution of different strategies to allow optimal matching to the environmental conditions that organisms can encounter in contrasting environments. For ectothermic animals, we need to disentangle the role of stage-specific thermal tolerances and developmental acclimation to predict the effects of climate change on spatial distributions. However, the interplay between these mechanisms has been poorly explored. Here we study whether developmental larval acclimation to rearing temperatures affects the thermal tolerance of subsequent terrestrial stages (metamorphs and juveniles) in common frogs (Rana temporaria). Our results show that larval acclimation to warm temperatures enhances larval heat tolerance, but not thermal tolerance in later metamorphic and juvenile stages, which does not support the developmental acclimation hypothesis. Further, metamorphic and juvenile individuals exhibit a decline in thermal tolerance, which would confer higher sensitivity to extreme temperatures. Because thermal tolerance is not enhanced by larval developmental acclimation, these 'risky' stages may be forced to compensate through behavioural thermoregulation and short-term acclimation to face eventual heat peaks in the coming decades.