The nutritional status of Heliophanus spiders shifts their food preferences for aphid prey over intraguild spider prey.

Spiders are dominant predators of agroecosystems, where they must adapt to regular disturbances. Recent studies show that their abundance in crop fields has declined, even at sites not sprayed with agrochemicals. These declines have been attributed mainly to reduced ecosystem complexity, which decreases herbivore populations and consequently limits the prey available to predators. Moreover, spiders, similar to other arthropods, are sensitive to frequent disturbances, such as plowing and mowing. In addition to these well-established drivers, undernourishment of spiders following repeated anthropogenic disturbance may further contribute to declines. We hypothesized that the food preferences of agrobiont spiders change in response to the previously provided diet. As a model, we used females of Heliophanus cupreus (Walckenaer, 1802) and Heliophanus flavipes (Hahn, 1832) (both Araneae: Salticidae), provided with Drosophila melanogaster Meigen, 1830 of various nutrient compositions, and then provided with a protein-rich intraguild prey represented by Dictyna Sundevaal, 1833 spiders and a lipid-rich agricultural pest prey represented by rose-grain aphids Metopolophium dirhodum (Walker, 1849). The prey preferences of the spiders changed in response to the previously provided diet. The lipid-rich diet increased spider survival and led to a preference for agricultural pest prey. In contrast, spiders on standard or protein-rich diets did not prefer agricultural pest or intraguild prey. Agrobiont spiders are able to adjust the spectrum of captured prey to pests dominating the respective crop type. However, the present findings suggest that the nutritional status of spiders may shape their food preferences, with potential, but untested, implications for predator-prey interactions in agroecosystems.