A molecular detection approach for assessing wheat aphid-parasitoid food webs in northern China

Abstract

In northern China, wheat aphids are widespread and pose serious threats to wheat crop yields. As parasitoids are important parasitic natural enemies of wheat aphids, their interactions with wheat aphids have received much attention. Traditional methods commonly cannot provide clear evidence of trophic links between primary parasitoids and hyperparasitoids or multiparasitism. To overcome this problem, we developed a molecular approach including three multiplex PCRs and five singleplex PCRs. With this approach, four wheat aphid species, four primary parasitoid species and eight to nine hyperparasitoid species were detected from aphid samples, which covered all the primary parasitoids and 94.8-98.1% of the hyperparasitoids found in wheat fields of northern China. The trophic interactions between aphids and primary parasitoids and between primary parasitoids and hyperparasitoids were determined, and a quantitative tri-trophic food web was established through molecular detection. The proportion of hyperparasitized samples was 53.36%, and multiparasitism was very common in the hyperparasitoid trophic interactions (22.02%). These results indicate that this approach is effective for revealing the complex wheat aphid-parasitoid-hyperparasitoid networks in northern China.