Local adaptation in trait-mediated trophic cascades dataset

Predator-induced changes in prey foraging can indirectly influence community dynamics by increasing the abundance of basal resources via a trait-mediated trophic cascade. The strength of these cascades may be altered by eco-evolutionary relationships between predators and prey, but the role of basal resources has received limited attention. We hypothesized that the strength of trait-mediated trophic cascades may be shaped by selection from trophic levels above and below prey. Our field and laboratory experiments utilized snails (Nucella lapillus) from two regions in the Gulf of Maine (GoM) that vary substantially in basal resource (e.g., barnacles, mussels) availability and invasion history with the predatory green crab, Carcinus maenas. Nucella from both regions were provided with mussels as a basal resource and exposed to the presence or absence of green crab risk cues. In both experiments, Nucella from the northern GoM, where basal resources are scarce, displayed weaker responses to risk cues than southern Nucella. In the lab, however, northern Nucella foraged more than southern snails under risk, but foraging rates among the two regions did not differ without risk. Our results suggest that adaptation to basal resource availability may contribute to geographic variation in the strength of trait-mediated trophic cascades.