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Dryad

Transgenerational effects of Aphidius platensis (Hymenoptera, Braconidae) on Schizaphis graminum (Hemiptera, Aphididae)

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Sep 25, 2026 version files 365.55 MB

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Abstract

Koinobiont parasitoids such as Aphidius platensis Brèthes (Hyme noptera: Braconidae) develop within living hosts and may alter host physiology and development to enhance parasitoid offspring performance. Aphids, however, can respond to natural enemies through a range of defensive strategies, including increased reproductive investment (fecundity compensation) and phenotypic plasticity, such as the production of winged morphs. 

This study examined whether successive generations of Schizaphis graminum (Rondani) (Hemiptera: Aphididae) exposed to the parasitoid A. platensis exhibit changes in parasitism rates and reproductive output. Aphid populations were maintained under two treatments across four generations: exposure to parasitoids and absence of parasitoids. 

Parasitism rates declined over generations in the exposed treatment, suggesting that repeated parasitoid pressure may induce host changes that reduce parasitoid developmental success. In all generations, aphids in the parasitoid-free treatment showed higher reproductive output than those exposed to parasitoids, providing no evidence for fecundity compensation. Additionally, parasitoid-free aphids produced more nymphs and winged adults than aphids exposed to parasitoids, indicating that parasitoid presence may not influence aphid polyphenism. 

Overall, the results suggest that S. graminum responses to parasitism by A. platensis can shift across generations, potentially reflecting rapid adjustments in host defense under sustained parasitoid pressure.