Ecology

The purpose of this study is to understand how the relationship between generational cattle ranchers and conservation efforts is changing given rapid development and urbanization within the state of Florida over the past decade. To understand this relationship, the author used participant observation in conjunction with ethnographic interviews to work with ranchers and individuals from the Green Paths Foundation to draw a comprehensive picture of how development has affected ranching and conservation efforts in Florida. With the help of cultural consultants, I was able to make additional connections within the ranching and conservation communities that helped to provide further context to the question being investigated in this thesis and to understand how Florida’s Conservation Corridor mediates between ranchers and conservation imperatives.

By regulating the abundance of prey populations, predators can directly and indirectly influence food web interactions in ways that influence ecosystem function. Predator functional responses quantify how predator foraging rate changes with prey abundance. Due to the large numbers of individuals needed for these experiments, most studies are conducted on small, abundant taxa. Consequently, we know relatively little about the functional responses of many marine taxa, especially those that are large and highly mobile. We present a novel method for studying predator foraging behaviors by integrating two innovative approaches: passive acoustics to document the occurrence of underwater predation events in concert with a recently developed statistical method that uses the times between predation events to estimate functional response parameters. We demonstrate and expand on the application of these methods by quantifying the shape of the predator functional responses for whitespotted eagle rays (Aetobatus narinari) preying on hard clams (Mercenaria mercenaria).

I used empirical data to inform spatially- and temporally-explicit predictions of time-integrated habitat availability (TiHAB), quantify spatiotemporal patterns of resource selection by Little Blue Herons (Egretta caerulea), and evaluate foraging activity as function of resource availability and prey dynamics. Evaluating resource availability over time accounts for the magnitude and duration of resource change. This approach is useful for understanding mechanisms that underlie resource selection in dynamic environments and for guilds that are sensitive to changes in prey availability like wading birds. I found that average TiHAB varied interannually whereby gains and losses in Little Blue Heron foraging habitat at the landscape scale (1-8 km) occurred from slight differences in annual tidal cycles otherwise imperceptible with water depth data alone. Local patterns of resource selection by Little Blue Herons were temporally consistent but spatially variable across tidally influenced environments. TiHAB was the most important habitat attribute over time and space and was superior to other environmental features and prey density as a predictor of Little Blue Heron resource selection. Foraging activity did not show a clear association with probability of resource selection, but foraging metrics were best described by changes in TiHAB consistent with changes in foraging strategy. I conclude that spatiotemporal variation in resource availability reliably predicts patterns of dynamic habitat selection and supports an energy-maximizing foraging strategy for wading birds in tidally influenced habitats. This modeling framework can be applied to quantify the spatiotemporal availability of resources in real-time or under hydrologic restoration regimes and sea level rise scenarios, and track species responses to hydrologic and other environmental fluctuations.

Gopher tortoise ecology is poorly understood in the rapidly developing, urbanized southeastern end of its range. This study reports on a population at Florida Atlantic University in Boca Raton, Florida. Burrow surveys were conducted from May to July 2003 and May to August 2004. Burrows were marked and mapped as was vegetative cover. Burrow locations were tested against vegetative cover height and soil types. Burrow locations did not differ among soil types. The densest concentrations of burrows were located in areas of low, patchy vegetative cover. This is consistent with known gopher tortoise habitat preferences elsewhere in their range. Gopher tortoises on this site appeared to be acclimated to anthropogenic disturbance.

The projects described in this dissertation are focused on compounds derived from the marine environment. Chapter 1 gives an introduction to the study of marine natural products to treat human ailments and a thorough review on compounds from lithistid sponges that have been isolated or synthesized since 2000. Chapter 2 describes the isolation and structure elucidation of two sesquiterpene substituted benzoquinone derivatives, petrosiquinones A and B, from a deep-water marine sponge from the Family Petrosiidae. Although initially purified following activity in a (Sb(B-catenin/Tcf4 assay they were later followed using tumor cell line cytotoxicity assays. Petrosiquinone A was the more active of the two compounds with moderate cytotoxicity in the DLD-1, PANC-1, and AsPC-1 cell lines. In Chapter 3, the isolation and structure elucidation of two new marine-derived macrolides, madeirolide A and B, isolated from a deep-water lithistid sponge of the genus Leiodermatium is described.

It can be difficult to disentangle the factors that determine population success in freshwater systems, particularly for organisms with disturbance-resistant life stages like aquatic invertebrates. Nevertheless, the effects of environmental variation and habitat structure on animal population success in wetlands are important for understanding both trophic interactions and biodiversity. I performed two experiments to determine the factors limiting crayfish (Procambarus fallax) and dragonfly (Family: Libellulidae) populations in wetland environments. A simulation of a dry-disturbance and subsequent sunfish (Family: Centrarchidae) re-colonization revealed that crayfish populations are sensitive to sunfish, while dragonfly naiads seemed to be limited by other drying-related factors. A second manipulation revealed that small-bodied fishes and habitat structure (submerged vegetation) shaped dragonfly communities primarily through postcolonization processes.

This study compared the avian communities of treatment wetlands in South Florida called Stormwater Treatment Wetlands (STAs) to those in natural marshes and crop lands, and examined factors that influenced the size and structure of the avian communities within the STAs. The STAs contained a more abundant, rich and distinct avian community compared to reference land types. The STAs were dominated by wintering waterfowl, and therefore community patterns fluctuated more seasonally other land types. Within the STAs, density and richness in the fall and winter were much greater in the submerged aquatic vegetation than in the mixed emergent vegetation when waterfowl were present. The STAs maintain two vegetation treatments which enhanced their biodiversity value by supporting distinct avian communities with different migratory strategies This suggests the increase in treatment wetlands could partially offset the loss of natural wetlands, but avian communities in treatment wetlands are not surrogates for natural wetlands.