Competitive Interactions of Two Species of Freshwater Turtles, a Generalist Omnivore and an Herbivore, Under Low Resource Conditions

Abstract

Abstract Under low-resource conditions, the outcome of competition between a generalist omnivore and an herbivore may depend on whether one species can more efficiently use a limiting resource. I evaluated the levels of omnivory and competitive interactions between two abundant sympatric emydid turtles, Trachemys scripta and Pseudemys floridana, that coexist across a productivity gradient in lakes in northern Florida. A foraging experiment indicated that both species were omnivorous in the juvenile stage, but P. floridana was more herbivorous and T. scripta consumed more insects and carrion. This low level of resource overlap was consistent with previous studies of gut contents and stable isotope analyses. In a 13-mo enclosure experiment in a natural pond under low-resource conditions, the generalist T. scripta grew more slowly with conspecifics than with P. floridana, and the more specialized P. floridana grew at the same rate with both T. scripta and conspecifics. Trachemys scripta with P. floridana exh...