Transgenerational plasticity mediates temperature effects on fitness in Daphnia magna

Phenotypic plasticity is an important way by which organisms respond to changes in their local environment, but it is not clear whether parents can buffer the negative impacts of high temperature on offspring fitness. To investigate this question, we exposed the waterflea Daphnia magna (Straus 1820) and their offspring to either low (15oC) or high (25oC) temperature in a crossed factorial design. High parental temperature reduced the age and size at reproductive maturation and resulted in smaller average clutch size, regardless of offspring temperature. This suggests that parents did not buffer the effects of high temperature on their offspring. However, offspring raised at high temperature that came from parents also raised at high temperature had similar adult body size and longer life span than offspring produced by parents exposed to low temperature. As a consequence of these apparent trade-offs, there was no detectable effect of parental temperature on offspring life time reproductive success. These results suggest that although transgenerational plasticity could help organisms to cope with stressful changes in their local environment, such effects might be difficult to detect in natural populations due to associated life history trade-offs.

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