Theory predicts that when prey can reach a size refuge from predation, prey vulnerability to predation is a function of hatchling size, growth rate, and the handling limitations of its predator, which collectively influence the amount of time prey spend vulnerable. I examined the mechanistic role of prey size for the predator-prey interaction between predatory crayfish (Procambarus fallax) and apple snail prey (Pomacea paludosa and P. maculata) and found that crayfish feeding rates decreased with snail size, such that smaller hatchling P. maculata were more than twenty times more vulnerable than hatchling P. paludosa. Experimental manipulations of productivity increased apple snail growth rates, reducing the effects of predatory crayfish on P. maculata survivorship, but not P. paludosa survivorship. My results indicate that when prey can reach a size refuge from predation, increased system productivity decreases predator limitation of that prey. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Invasion of exotic species is a global threat to native species, biological diversity, and ecological restoration projects. Pomacea maculata is a macrophyte herbivore often misidentified with one of the world’s most invasive and destructive exotic snail, Pomacea canaliculata, but has a broader geographical distribution and climate tolerance, and greater egg production. This research examines whether the exotic P. maculata and native Pomacea paludosa occupy identical vegetation communities, mechanisms of interference competition, grazing impact differences on Vallisneria americana and to develop an exploratory agent based model. This model uses historical and present data to project how differences between species in life history and grazing patterns can potentially impact South Florida ecosystems. This model examined how P. maculate invasion of South Florida could affect two of the Central Everglades Planning Project’s main environmental restoration goals: function of key vegetative communities and conservation of endangered or threatened species. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection