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Titre de la présentation : "Molecular analyses of trophic interactions to unveil the role of landscape context on the biological control of cereal aphids. Predators AND/OR/NOT parasitoids”

Summary:

The abundance and diversity of natural enemies increase with higher landscape complexity. However, this can also promote the increase of negative interactions (such as intraguild predation (IGP)), being detrimental for the efficiency of biological control of pests. In this research, the influence of landscape complexity on the population dynamics and trophic interactions of aphids and their main natural enemies (coccinellid beetles and Aphidiinae parasitoids) were investigated.

To detect trophic links among predator-prey, parasitoid-host, and predator-parasitoid interactions, DNA-based analyses were applied. A new set of molecular markers (novel species-specific and group-specific primer pairs) was used to allow the detection of the most abundant coccinellid species, cereal aphids, and their associated parasitoids. Using DNA-based gut-content analyses to detect direct and coincidental IGP and aphid consumption, we observed that with higher predator abundances, the aphid consumption increases in fields surrounded by complex landscapes, and the consumption of parasitized aphids is mostly detected early in the season, and with a detrimental effect on the parasitoid population build-up. In contrast with expected predictions, we found little evidence that landscape complexity affects negative interactions, demonstrating that direct IGP among coccinellid beetles is a common interaction in this system, independently of the landscape.

Finally, we highlighted the importance of different natural enemy groups and their temporal dynamics under contrasting agricultural contexts to understand the relationship between diversity and the efficiency of biological control of aphids.