Subject Editor: Rachid HannaPredatory interactions form food webs and shape ecosystems. Such predator-prey relationships underlie the survival, fitness, and landscape utilization of predatory arthropods. Synanthropic arthropod species thrive in agroecosystems and in other landscapes transformed by human activity. Understanding the characteristics of synanthropic arthropod predator-prey relations is crucial to understanding and mitigating their impacts in nonnative ranges. One way to quantify predation is via the functional responses, which describe the strength and nature of predator-prey interactions. Predator traits and environmental conditions can influence functional responses, the resulting energy and nutrient flows, and ultimately population dynamics. Here, we present the first functional response quantification for the European harvestman (Phalangium opilio L.), an introduced opilionid species in the United States. We explore how predator sex, body size, leg characteristics, and environmental light levels influence foraging rates of wild-caught P. opilio on midge prey. We find that P. opilio exhibits a type II functional response on midges, and that predator sex, environmental light conditions, and many continuous predator characteristics such as body size and leg length do not influence functional response parameters. The number of legs missing also did not influence functional response parameters. Our results show that foraging rates in this species are primarily driven by prey density, while many classic determinants of interaction strengths do not appear to alter foraging. Our results improve our understanding of the role of nonnative predators in food webs and highlight the need for species-specific functional response experiments to quantify interaction strengths between novel predators and native prey.
Stowe et al. (Sun,) studied this question.