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Extra molting and selection on nymphal growth in the desert locust

Pélissié B., Piou C., Jourdan H., Pagès C., Blondin L., Chapuis M.P.. 2016. PloS One, 11 (5) : e0155736 (18 p.).

In insects, extra-molting has been viewed as a compensatory mechanism for nymphal growth that contributes to optimize body weight for successful reproduction. However, little is known on the capacity of extra-molting to evolve in natural populations, which limits our understanding of how selection acts on nymphal growth. We used a multi-generational pedigree, individual monitoring and quantitative genetics models to investigate the evolution of extra-molting and its impact on nymphal growth in a solitarious population of the desert locust, Schistocerca gregaria. Growth compensation via extra-molting was observed for 46% of the females, whose adult weight exceeded by 4% that of other females, at a cost of a 22% longer development time. We found a null heritability for body weight threshold only, and the highest and a strongly female-biased heritability for extra molting. Our genetic estimates show that (1) directional selection can act on growth rate, development time and extra-molting to optimize body weight threshold, the target of stabilizing selection, (2) extra-molting can evolve in natural populations, and (3) a genetic conflict, due to sexually antagonistic selection on extra-molting, might prevent its fixation. Finally, we discuss how antagonistic selection between solitarious and gregarious environments and/or genetic correlations between growth and phase traits might also impact the evolution of extra-molting in locusts. (Résumé d'auteur)

Mots-clés : schistocerca gregaria; génétique des populations; Évolution; mutation; croissance; héritabilité

Thématique : Ravageurs des plantes; Ecologie animale

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