Location: Integrated Cropping Systems ResearchTitle: Predator community structure and trophic linkage strength to a focal prey
Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2013
Publication Date: 7/23/2014
Citation: Lundgren, J.G., Fergen, J.K. 2014. Predator community structure and trophic linkage strength to a focal prey: the influence of the prey’s anti-predator defense. Molecular Ecology. 23:3790-3798.
Interpretive Summary: There is debate among scientists whether predator diversity is a good thing for biological control of insect pests. On one hand, more predators and more predator species could mean greater pressure on a focal pest. But generalist predators don’t just eat pests, they also eat each other and this could disrupt predation on a pest. We examined soil predator communities in 16 corn fields over two years, characterized their diversity, abundance, and evenness (whether predators were equally abundant, or were skewed toward a few very abundant species). Then we examined their gut contents, looking for DNA fragments of the infamous pest, Western Corn Rootworm. We found that the frequency that predators consumed rootworms increased as predator abundance and diversity within the cornfield increased. This was particularly true for chewing predators, which are known to be more affected by the rootworms' defenses. We conclude that rootworms are an unpreferred prey, and will only be consumed after predators have exploited palatable or preferred species in the cornfields. Thus, predator community diversity and abundance are key to managing rootworms using conservation biological control.
Technical Abstract: Predator abundance and community structure can increase or decrease the suppression of lower trophic levels, although studies of these interactions under field conditions are relatively few. We investigated how the frequency of consumption (measured using PCR-based gut analysis) is affected by predator abundance, community diversity and evenness under realistic conditions. Soil arthropod communities in sixteen maize fields were measured (number of predators, diversity [Shannon H], and evenness [J]) and predator guts were searched for DNA of the focal subterranean herbivore, the corn rootworm (Diabrotica virgifera). Predator abundance and diversity were positively correlated with trophic linkage strength (the proportion positive for rootworm DNA), although the latter characteristic was not significantly so. The diversity and evenness of the predator community with chewing mouthparts was strongly correlated with their linkage strength to rootworms, whereas the linkage strength of fluid-feeding predators were unaffected by their community characteristics. Chewing predators are more affected by the rootworm’s hemolymph defense. This research clearly shows that predator abundance and diversity influences the strength of a community’s trophic linkage to a focal pest, and that these community characteristics may be particularly important for less palatable or protected prey species. We also make the case for conserving diverse and abundant predator communities within agroecosystems as a form of pest management.