Abstract

The trophic interactions between predators can vary depending on the abundance of their prey. In the alfalfa fields of central Chile, coccinellids (Coleoptera: Coccinellidae) are the main natural enemies of aphids (Hemiptera: Aphididae), whose populations vary throughout the season. Coccinellids can forage for alternative prey, remaining in the crops when target pests are scarce, favoring their presence before the pest arrives and improving biological control. Therefore, knowledge of the different predator-prey interactions in different scenarios of prey availability has gained great importance. Based on DNA metabarcoding analysis, we describe the diet of the most abundant coccinellid species in alfalfa fields and how food web varies in scenarios of higher and lower aphid abundance. Additionally, we analyzed the consumption of alternative prey, such as pollen. The results revealed a set of generalist predators with high stability in their trophic interactions regardless of aphid abundance. However, Hippodamia variegata (Goeze) is less generalist than Eriopis chilensis Hofmann and Harmonia axyridis (Pallas). The native E. chilensis has a stable consumption of aphids, and other important pests are exclusively preyed by this species. Pollen is frequently consumed by these coccinellids, E. chilensis and H. variegata, which remain in alfalfa throughout the season, increasing its consumption during periods of lower aphid abundance. Aphids are the key prey for the permanence of H. axyridis in these crops. This study shows that coccinellids consume a variety of prey and alternative resources, allowing some species to persist in the fields when aphids are scarce.