Doctoral Dissertation Defense by Eleanor DiNuzzo: The impacts of a non-native predator on a resident trophic cascade
Abstract:
Predators are important drivers of community dynamics and composition, exerting a strong influence on species in lower trophic levels. Predators influence prey by either directly consuming them or scaring them (i.e., predation risk effects), both of which can scale up to have population-level consequences. Thus, examining predator-prey dynamics is a crucial piece to comprehend how communities function. As the introductions of non-native species are accelerating worldwide though, existing predator-prey dynamics are becoming increasingly difficult to predict and examine. Previous work shows that examining the impact of non-native species in the context of a multi-species food chain, such as trophic cascades, can improve our understanding of the impact non-natives have and that exploring the multiple different trophic links non-native species has is crucial to assess their impact communities instead of singular dyadic interactions. However, most studies do not account for the traits of non-native species, such as changing body size, that may change over time and result in dynamic, complex interactions between non-native and resident predators that have previously not been accounted for. Thus, for my dissertation, I investigated how a non-native predator at two different stages of ontogeny disrupts a resident trophic cascade via 1) nonconsumptive effects and 2) consumptive effects, and 3) if the non-consumptive effects differ between intraspecific and interspecific predator interactions using a well-known rocky intertidal system. This system consists of the predatory green crab, Carcinus maenas, its prey the dogwhelk snail, Nucella lapillus, the basal resource the blue mussel, Mytilus edulis, and the recently invaded predator the Asian shore crab, Hemigrapsus sanguineus. I ran a series of three laboratory mesocosm experiments and found that 1) Hemigrapsus had significant non-consumptive effects resulting in increased refuge use and reduced foraging and growth in Nucella, and that when both predators were together Nucella had weaker risk responses than expected regardless of Hemigrapsus body size. 2) Hemigrapsus had risk reducing emergent multiple predator effects on shared prey mortality, but those effects varied in some contexts depending on Hemigrapsus body size and the presence of alternate prey. 3) The type of refuge Nucella used differed between the intraspecific and interspecific predator interactions between Hemigrapsus and Carcinus, but not Nucella foraging or tissue growth. This work highlights the importance of accounting for multi-species interactions to provide a more comprehensive picture of non-native species impacts on resident species interactions and communities.
Committee members:
Dr. Nancy O'Connor, Biology Department, UMass Dartmouth;
Dr. Diego Bernal, Biology Department, UMass Dartmouth;
Dr. David Kimbro, Marine and Environmental Sciences Department, Northeastern University
Advisor(s): Dr. Michael Sheriff and Dr. Sarah Donelan, Biology Department, UMass Dartmouth
SENG 115
Michael Sheriff
msheriff@umassd.edu