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Seasonal variations of host resources influence foraging strategy in parasitoids

Abstract : Many species have to cope with decreased resource availability and life expectancy during winter. The optimal foraging theory predicts that under these conditions, generalist foraging strategies should be favoured, via the acceptance of suboptimal resources. In contrast, during favourable seasons, specialist foraging strategies, i.e., a preferential consumption of the most profitable resources, should be favoured instead. Although spatial and fine-scale temporal dimensions of the influence of resource distribution on foraging strategies have long been studied in individual species, guild-level, large-scale temporal approaches (over multiple seasons) have rarely been considered. Parasitoids that can remain active during winter are an interesting model system which allows direct testing of resource profitability and reaching conclusions about foraging strategies from an evolutionary point of view. Here, we analysed how temporal variations of host resource availability in northwestern France impact the foraging strategies of parasitoid wasps. The foraging behaviours of dominant cereal aphid parasitoid species in relation to the two most abundant aphid host species were observed in winter and in spring. Because of a seasonal change in the host–parasitoid community and of a few species present in the fields each season, we were unable to confirm our hypothesis at the species level for all the studied species. Nevertheless, this study brought results consistent with our assumptions at the guild level, indicating that different species of a guild favour similar foraging strategies. In winter, female parasitoids generally adopted an opportunistic strategy, accepting all aphid hosts encountered, even if they were suboptimal. In spring, parasitoids displayed a specialist strategy by selecting preferentially a host species, but the better quality of preferentially selected species remains to be fully demonstrated.
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Delphine Eoche-Bosy, Yannick Outreman, Thiago Oliveira Andrade, Liliane Krespi, Joan van Baaren. Seasonal variations of host resources influence foraging strategy in parasitoids. Entomologia Experimentalis et Applicata, Wiley, 2016, 161 (1), pp.11-19. ⟨10.1111/eea.12494⟩. ⟨hal-01406208⟩

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