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Host–parasite interaction; in vitro fertilisation; paternal effects; sperm phenotype; three-spined stickleback
Abstract:
Forces shaping an individual’s phenotype are complex and include transgenerational effects.
Despite low investment into reproduction, a father’s environment and phenotype can shape its
offspring’s phenotype. Whether and when such paternal effects are adaptive, however, remains
elusive. Using three-spined sticklebacks in controlled infection experiments, we show that sperm
deficiencies in exposed males compared to their unexposed brothers functionally translated into
reduced reproductive success in sperm competition trials. In non-competitive fertilisations, offspring
of exposed males suffered significant costs of reduced hatching success and survival but
they reached a higher body condition than their counterparts from unexposed fathers after experimental
infection. Interestingly, those benefits of paternal infection did not result from increased
resistance but from increased tolerance to the parasite. Altogether, these results demonstrate that
parasite resistance and tolerance are shaped by processes involving both genetic and non-genetic
inheritance and suggest a context-dependent adaptive value of paternal effects.
