TEMPERATURE, RESOURCE INPUT, AND STANDING GENETIC VARIATION AFFECT PREDATOR RESPONSES OF PHYSA ACUTA

Abstract

In urban areas, features such as high percentages of impervious ground cover, patchiness, and storm water runoff can lead to increases in temperature and external nutrient input into aquatic systems. Such factors can lead to changes in primary productivity, and thus the growth rates of primary consumers, as well as the vulnerability of primary consumers to predation. Additionally, isolated populations due to patchiness of natural areas in urban environments can lead to inbred populations, which can also influence growth rates and vulnerability of primary consumers. To assess how such factors can influence interspecific interactions, we test how temperature, resource availability, and standing genetic variation of the freshwater snail Physa acuta affects the snail's anti-predator responses and life history characteristics. We conducted an experiment in which we reared snails from inbred or wild-caught lineages at high or low temperatures, with high and low resource inputs, and with or without chemical cues of crayfish (Procambarus clarkii) predation. We assessed how these treatments affected predator avoidance behavior, anti-predator morphological responses, reproductive output, and survival. We found that snails reared in high temperatures, and with low resource availability were unable to exhibit typical morphological responses to predators. We also found that snails were more likely to exhibit anti-predator behaviors when resource availability was low and when temperatures were high, and that behavioral responses to predators were higher for inbred snails than wild-caught snails. Snail survival was significantly affected by temperature, resource availability, and standing genetic variation. Reproductive output of snails was also affected by temperature, resource availability, predator cue presence, and standing genetic variation. These results indicate that features common in urban systems can influence not only individuals' ability to persist in these environments, but also can have effects on species interactions in ways that can cascade through food webs and potentially change ecosystem functions.