Washington State Potato Commission: Who's Eating Who? Molecular Detection of Predator Diets in Washington Potatoes

Predators will be screened by PCR for prey DNA to identify the complex of natural enemies most likely to impact pest species in Washington potato agroecosystems, both spatially and temporally. Sampling will be undertaken throughout the season, specimens mailed to the University of Kentucky and molecular protocols followed to identify trophic connectance at both high and low prey densities, and identify prey selectivity under natural field conditions. The DNA-based detection protocols (developed in the laboratory of the PI) will be utilized to study food web structure will identify those predators feeding on key pests, and those natural enemies most likely to exert greatest pressure in biological control programs. Furthermore, some predators feed on pests at disproportionately high rates early in the season, before populations increase. Although such a phenomenon has not been demonstrated in carabids, early-season monitoring will be undertaken to ensure accurate determination of food web structure. All specimens collected in the field will be transferred into 1.5 ml microcentrifuge tubes or 7 ml disposable plastic containers and stored at -20°C until gut extraction. The extraction of DNA will follow published protocols using Qiagen Extraction Kits, and techniques recently optimized within the laboratory of the PI. Based upon preliminary research at this field site, approximately 2,000-3,000 predators will be collected throughout the field season. This is a highly successful protocol for the collection of gut samples for molecular gut-content analysis. All predators will be identified while on ice. The mass screening of2,000 - 3,000 predators by PCR will be undertaken throughout the year by postdoctoral scholar, Dr. Eric G. Chapman, and assisted by an undergraduate student. The PCR approach provides an accurate and rapid assessment of predator gut content and will enable feeding behavior of predator communities to be evaluated. Throughout the season, the proportion of predators screening positive for prey DNA will be correlated with prey availability to identify potentially coupled relationships between organisms, and estimate the role of natural enemies in biological control.