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Individuals can respond to predation risk by building morphological defenses or by altering their behavior. We tested whether freshwater Physa acuta (Draparnaud, 1805) snails with better morphological defenses against predation risk displayed lower or higher behavioral responses to predator cues compared to more poorly defended snails. We examined how the morphological traits of snails influence their risk of predation by crayfish, inferred by crush resistance, and how those same traits also influence their patch use in the absence and presence of predator cues. Using model selection, we found that a large shell width increased crush resistance. We also found that other morphological traits interacted with predator cues to influence the use of high resource patches, however shell width had almost no influence. Aperture length and aperture width both strongly interacted with cue: larger aperture length and larger aperture width snails decreased their use of the high resource patch substantially. ...

Phenotypic expression can be altered by direct perception of environmental cues (within-generation phenotypic plasticity) and by the environmental cues experienced by previous generations (transgenerational plasticity). Few studies, however, have investigated how the characteristics of phenotypic traits affect their propensity to exhibit plasticity within and across generations. We tested whether plasticity differed within and across generations between morphological and behavioral anti-predator traits of Physa acuta, a freshwater snail. We reared 18 maternal lineages of P. acuta snails over two generations using a full factorial design of exposure to predator or control cues and quantified adult F2 shell size, shape, crush resistance, and anti-predator behavior – all traits which potentially affect their ability to avoid or survive predation attempts. We found that most morphological traits exhibited transgenerational plasticity, with parental exposure to predator cues resulting in larger and more crush-resistant offspring, but shell shape demonstrated within-generation plasticity. In contrast, we found that anti-predator behavior expressed only within-generation plasticity such that offspring reared in predator cues responded less to the threat of predation than control offspring. We discuss the consequences of this variation in plasticity for trait evolution and ecological dynamics. Overall, our study suggests that further empirical and theoretical investigation is needed in what types of traits are more likely to be affected by within-generational and transgenerational plasticity.

Prairie potholes are the dominant wetland type in the intensively cultivated northern Great Plains of North America, and thus have the potential to receive pesticide runoff and drift. We examined the presence of pesticides in sediments of 151 wetlands split among the three dominant land use types, Conservation Reserve Program (CRP), cropland, and native prairie, in North and South Dakota in 2011. Herbicides (glyphosate and atrazine) and fungicides were detected regularly, with no insecticide detections. Glyphosate was the most detected pesticide, occurring in 61% of all wetlands, with atrazine in only 8% of wetlands. Pyraclostrobin was one of five fungicides detected, but the only one of significance, being detected in 31% of wetlands. Glyphosate was the only pesticide that differed by land use, with concentrations in cropland over four-times that in either native prairie or CRP, which were equal in concentration and frequency of detection. Despite examining several landscape variables, such as wetland proximity to specific crop types, watershed size, and others, land use was the best variable explaining pesticide concentrations in potholes. CRP ameliorated glyphosate in wetlands at concentrations comparable to native prairie and thereby provides another ecosystem service from this expansive program.