title: Are aphid parasitoids from mild winter climates losing their winter diapause?
abstract: Temperature is both a selective pressure and a modulator of the diapause expression in insects from temperate regions. Thus, with climate warming, an alteration of the response to seasonal changes is expected, either through genetic adaptations to novel climatic conditions or phenotypic plasticity. Since the 1980s in western France, the winter guild of aphid parasitoids (Hymenoptera: Braconidae) in cereal fields has been made up of two species: Aphidius rhopalosiphi and Aphidius matricariae. The recent activity of two other species, Aphidius avenae and Aphidius ervi, during the winter months suggests that a modification of aphid parasitoid overwintering strategies has taken place within the guild. In this study, we first performed a field survey in the winter of 2014/15 to assess levels of parasitoid diapause incidence in agrosystems. Then, we compared the capacity of the four parasitoid species to enter winter diapause under nine different photoperiods and temperature conditions in the laboratory. As predicted, historically winter-active species (A. rhopalosiphi and A. matricariae) never entered diapause, whereas the species more recently active during winter (A. avenae and A. ervi) did enter diapause but at a low proportion (maximum of 13.4 and 11.2%, respectively). These results suggest rapid shifts over the last three decades in the overwintering strategies of aphid parasitoids in Western France, probably due to climate warming. This implies that diapause can be replaced by active adult overwintering, with potential consequences for species interactions, insect community composition, ecosystem functioning, and natural pest control.
authors.affiliation: UMR 6553 Ecobio, Centre National de la Recherche Scientifique, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes, France. tougeron.kevin@gmail.com.|Université Bretagne Loire, Cité Internationale, 1 place Paul Ricœur, 35044, Rennes, France. tougeron.kevin@gmail.com.|Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 rue Sherbrooke Est, Montréal, Quebec, H1X 2B2, Canada. tougeron.kevin@gmail.com.
authors.forename: Kévin
authors.identifier: 0000-0003-4897-3787
authors.initials: K
authors.lastname: Tougeron
authors.affiliation: UMR 6553 Ecobio, Centre National de la Recherche Scientifique, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes, France.|Université Bretagne Loire, Cité Internationale, 1 place Paul Ricœur, 35044, Rennes, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Le Lann
authors.affiliation: Département de Sciences Biologiques, Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 rue Sherbrooke Est, Montréal, Quebec, H1X 2B2, Canada.
authors.forename: Jacques
authors.initials: J
authors.lastname: Brodeur
authors.affiliation: UMR 6553 Ecobio, Centre National de la Recherche Scientifique, Université de Rennes 1, 263 Avenue du Général Leclerc, 35042, Rennes, France.|Université Bretagne Loire, Cité Internationale, 1 place Paul Ricœur, 35044, Rennes, France.
authors.forename: Joan
authors.initials: J
authors.lastname: van Baaren
mesh_terms: D000818:Animals; D001042:Aphids; D017753:Ecosystem; D006927:Hymenoptera; D012621:Seasons; D013696:Temperature
keywords: Climate change; Loss of diapause; Overwintering; Phenology; Phenotypic plasticity; Seasonal adaptations