Date of Award

12-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

Arthur C. Echternacht

Committee Members

David A. Buehler, Susan E. Riechert, Daniel Simberloff

Abstract

Invasive species often displace ecologically-similar native species, but the extent to which invading and displaced species function similarly in the food web processes of invaded communities is largely unknown. I investigated whether populations and individuals of an invasive Anolis lizard (the brown anole, Anolis sagrei) and the native congener it displaces in Florida (the green anole, Anolis carolinensis) are functionally equivalent in the food webs of open and structurally-simple habitats. In a system of invaded and uninvaded dredge-spoils islands, I found that both arthropod communities and winter bird communities covaried with brown anole abundance (and therefore the identity of the dominant anole species operating in island food webs) in ways that were generally well explained as the direct and indirect food web effects of greater Anolis predation pressure on arthropods following brown anole invasion. Larger-bodied ground and foliage-dwelling arthropods tended to be negatively associated with brown anole abundance, as was total foliage arthropod abundance; by contrast, smaller-bodied arthropods, which are less likely to serve as brown anole prey, tended to be positively associated with brown anole abundance. The abundances of arthropod-consuming birds were also negatively associated with brown anole abundance, possibly reflecting exploitative competition for prey. Although many of the observed patterns were partly or entirely co-explained by environmental and spatial covariables, both statistical evidence and mechanistic considerations strongly suggested that at least some arthropod response groups were differentially affected by green anole and brown anole populations. To evaluate the potential contribution of anole perching and foraging behavior to differential population-level effects, I compared the per-capita effects of male green and brown anoles for several arthropod prey taxa that were stocked, over a series of experiments, into field enclosures erected over small cabbage palms (Sabal palmetto). Despite significant differences in every measured behavioral attribute, male green and brown anoles had statistically indistinguishable effects on six of seven prey taxa, suggesting that individuals of these two species have similar per-capita effects on prey assemblages when they forage in spatially-proximate locations. This dissertation represents one of the few existing comparisons of the relative food web effects of terrestrial vertebrate predators.

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