Abstract
Transgenerational plasticity (TGP) occurs when the environment encountered by one generation (F0) alters the phenotypes of one or more future generations (e.g. F1 and F2). Selective inheritance of ancestral environments, via specific lineages or to only male or female descendants, may be adaptive if it allows past generations to fine-tune the phenotypes of future generations in response to sex-specific life history strategies. Here, we reared F1 offspring of unexposed and predator-exposed threespined stickleback (Gasterosteus aculeatus) fathers under ‘control’ conditions and generated F2s with a predator-exposed maternal and/or paternal grandfather. Grandpaternal effects were both sex and lineage-specific: female F2s were heavier and reacted less strongly to a simulated predator attack when their paternal grandfather was exposed to predation risk while male F2s were bolder when their maternal grandfather was exposed to predation risk. Therefore, grandpaternal effects were mediated across sexes, from F1 males to F2 females and from F1 females to F2 males. However, these patterns were only evident when one grandfather, but not both grandfathers, were exposed to predation risk. This selective inheritance may mean that grandparental effects are underestimated in the literature and raises new questions about the proximate and ultimate causes of selective transmission across generations.
