Location: Integrated Cropping Systems ResearchTitle: Dietary supplementation with non-prey food enhances fitness of a predatory arthropod Author
Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2013
Publication Date: 12/1/2013
Citation: Schmidt, J., Peterson, J., Lundgren, J.G., Harwood, J.F. 2013. Dietary supplementation with non-prey food enhances fitness of a predatory arthropod. Entomologia Experimentalis et Applicata. 149:282-291. Interpretive Summary: Most people regard spiders as strict predators, but this oversight ignores the importance of alternative foods like pollen and nectar in spider health and reproduction. Here, we examined how adding pollen to prey-based diets (springtails) affected various aspects of moneypenny spider (Mermessus fradeorum; Linyphiidae) performance. Although pollen had lower nutrient content than prey (less protein [N]), adding pollen to the springtail diet increased survival, nutrient reserves, and offspring production in spiders relative to a springtail-only diet. Thus, non-prey foods can be an important dietary component of predator’s diets, which influences when and where spiders will be found in cropland and how well they will control agricultural pests.
Technical Abstract: Uncertainties exist about the value of non-prey food for natural enemies that are commonly food limited, and the dietary conditions where non-prey foods are beneficial for carnivorous species. We examined the nutritional role of a non-prey food using a ground dwelling, tangle web-building spider that intercepts large quantities of pollen in their webs. These predators were provided diets of prey or no prey in the presence and absence of pollen. Treatment effects were quantified by measuring changes in predator body nutrient composition, survival, body size, and offspring production. Per dry weight, pollen had less nitrogen and lipids than prey, although relative quantities of these nutrients per meal were not measured. Dietary treatments altered the body tissue composition of the spiders, leading to the highest N content and lipid reserves in spiders provided with Collembola. Supplementing diets with pollen increased both juvenile and adult survival, and the greatest survivorship and offspring production was observed when spiders were provided diets of Collembola supplemented with pollen. Our results show that plant material such as pollen has positive effects on nutritional status and survival of a carnivorous species, and suggests that foraging on plant material promotes population growth at early and late developmental stages by supplementing diets of poor quality prey, and preventing starvation when prey are scarce.