Disentangling plasticity from local adaptation in diapause expression of parasitoid wasps from contrasting thermal environments: a reciprocal translocation experiment

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Tougeron, Kévin | van Baaren, Joan | Llopis, Stéphanie | Ridel, Aurélien | Doyon, Josée | Brodeur, Jacques | Le Lann, Cécile

Edité par CCSD ; Linnean Society of London -

International audience. An important question in evolutionary ecology is to understand the drivers of phenotypic variations in contrasted environments. Disentangling plasticity from evolutionary responses in such contexts allows a better knowledge of how organisms adapt their phenotypes to changing climates. Various aspects of the seasonal ecology of insect populations are essential for their persistence in the environment, including their capacity to overwinter. Phenotypic plasticity should allow insects to adjust their locally adapted diapause levels to actually experienced environmental conditions. Using an outdoor reciprocal translocation experimental design, we compared diapause expression of Canadian and French populations of aphid parasitoid species of the genus Aphidius in both their respective and foreign bioclimatic regions, thus mostly varying temperature conditions under similar latitude (i.e. same photoperiod). From June to December 2016, diapause and mortality levels were recorded every two weeks. We found both genotypic (populations " origins) and environmental effects (experimental locations) on diapause reaction norms of parasitoid species. The incidence of diapause was higher in Canadian populations (up to 90%) than French populations (<20%) at either location, suggesting local adaptations to harsh (Canadian populations) or mild (French populations) winter climatic conditions in their area of origin. Phenotypic plasticity played an important role in mediating diapause incidence at different temperatures but similar photoperiods, as diapause was induced at higher levels in Canada than in France, independently of parasitoid " s origin. We conclude that both plastic and evolutionary responses could be involved in the adaptation of parasitoids " overwintering strategies to different thermal environments and to ongoing climate warming.

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