Ectoparasitism and the Trade-Off between Current and Future Reproduction

Abstract

Ectoparasites are an ubiquitous element of the natural environment of most organisms, and by their effect on reproductive success of the host they are likely to affect the life-history trade-off between current and future reproduction. Since parents are in control of parental effort, they can compensate for the effect of ectoparasites on the current offspring by an increase in the rate of food provisioning to the nest. An increase in parental effort will enhance current reproductive success, but as predicted by the trade-off and tested here, the parents' future reproductive success will be impaired. Among passerine birds, the blue tit shows the highest prevalence and intensities of infection of the nest with ectoparasitic hen fleas. For blue tits (Parus caeruleus) we show experimentally that ectoparasitic hen fleas (Ceratophyllus gallinae) affect both the parents' likelihood to return as a breeder the year following ectoparasite exposure and their subsequent reproductive performance, suggesting that ectoparasites can modify this life-history trade-off. Our study suggests that parents pay the cost of ectoparasitism by a reduction in future reproductive success, which may be mediated by the increase in current parental effort, as predicted by life-history models.