Neglected patterns of variation in transgenerational plasticity: The importance of different sources of environmental variation differs across ages and sexes in a cyprinid fish

Adaptive transgenerational plasticity (TGP) requires individuals to integrate environmental experience across multiple sources. However, few empirical studies have considered that the relative relevance of certain sources might vary across ontogeny and sexes. Here, we address this knowledge gap by studying inducible antipredator defences, one of the most convincing examples of TGP. We assessed individual and combined effects of perceived high predation risk in mothers, fathers, caring males and personal environments on the morphology of juvenile, adult male and adult female cyprinids Pimephales promelas. Parental rather than personal environmental experience determined morphological defence expression across ages and sexes, likely because parents had a longer sampling period. In juveniles and adult males, egg‐mediated environmental experience outweighed sperm‐mediated environmental experience in the induction of body shape differences, likely because eggs can transmit information beyond epigenomes. However, in adult females, where body shape responses can be interpreted as life‐history plasticity, information from egg and sperm were equally important, likely resulting from different integration mechanisms between morphological and life‐history plasticity. The importance of care‐mediated relative to gamete‐mediated variation changed between juveniles and adult males, likely because they represent short‐ and long‐term environmental experience, respectively. Instead, in adult females, both sources were again equally important, potentially owing to lag‐times of life‐history plasticity. Parental care intensity only contributed marginally to defence formation. These results highlight age‐ and sex‐specific prioritization of different environmental experiences so as to generate optimal phenotypes. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.