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GCE III - Key Finding in 2015

    Mobile predators structure communities

    Large-bodied top predators are often highly mobile, with the potential to provide important linkages between spatially distinct food webs. In a series of studies of the American Alligator, Nifong found evidence that alligators can be an important consumer of blue crabs (Nifong et al. 2012), and that their presence can result in non-consumptive effects in crab behavior that indirectly affect blue crab consumption of ribbed mussels and periwinkle snails (Nifong and Silliman 2013). They also demonstrated that gut contents of alligators included numerous salt marsh species. More recently, Nifong et al. (2015) found that alligators in marine/estuarine habitats were significantly larger than those captured in freshwater and intermediate habitats, with clear differences in the stable isotope signatures among size classes (Fig. 1). Rosenblatt et al. (2015) examined the implications of these findings for individual niche specialization. This series of studies demonstrates that apex predators can exert strong top-down effects in ecological communities, and that cross-ecosystem foraging behavior is influenced by intrapopulation characteristics (body size, sex, individual specialization).

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    Fig. 1 δ13C and δ15N values of Alligator mississippiensis subpopulation groups [black diamond is small juvenile (TL>79 cm), black square is large juvenile (TL=79-100 cm), black triangle is subadult (TL=100-183 cm), and black circle is adult (TL>183 cm)], marine/estuarine primary producers (dark grey circles), marine/estuarine prey species (dark grey triangles), freshwater/upland primary producers (light grey circles), and freshwater/upland prey species (light grey triangles). Error bars are not included for prey species. From Nifong et al. 2015.



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This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.