Are aphid parasitoids from mild winter climates losing their winter diapause?

Area of Science:

• Ecology
• Entomology
• Climate Change Biology

Background:

• Temperature influences insect diapause, a key overwintering strategy.
• Climate warming prompts shifts in insect seasonal responses via adaptation or plasticity.
• Aphid parasitoid guilds in French cereal fields have historically included Aphidius rhopalosiphi and Aphidius matricariae.

Purpose of the Study:

• Investigate changes in aphid parasitoid overwintering strategies in response to climate warming.
• Assess diapause incidence in key aphid parasitoid species in Western France.
• Compare the diapause induction capacity of four aphid parasitoid species under varying environmental conditions.

Main Methods:

• Conducted a field survey of parasitoid diapause incidence during winter 2014/15.
• Performed laboratory experiments exposing four aphid parasitoid species to nine photoperiod and temperature regimes.
• Quantified diapause incidence across species and conditions.

Main Results:

• Historically winter-active species (A. rhopalosiphi, A. matricariae) did not enter diapause.
• Recently active winter species (A. avenae, A. ervi) exhibited low diapause incidence (max 13.4% and 11.2%).
• Results indicate a shift from diapause to active adult overwintering in this guild.

Conclusions:

• Aphid parasitoid overwintering strategies in Western France have rapidly shifted over three decades, likely driven by climate warming.
• The replacement of diapause by active overwintering has potential ecological implications.
• Changes may affect species interactions, community composition, ecosystem function, and biological pest control.