Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Forestry and Environmental Conservation
Committee Chair/Advisor
Kyle Barrett
Committee Member
Robert Baldwin
Committee Member
Luke Bower
Committee Member
Brandon Peoples
Abstract
Ecological interactions such as predation are vital to shaping the distribution of organisms. For interactions to occur, organisms must undertake movement, such as dispersal, that places them in proximity to the organisms with which they may interact. Geographically isolated wetlands (GIW) are productive and biodiverse ecosystems, but little is known on broad geographic scales about the determinants of their fauna. Fishes have difficulty colonizing GIW, whereas amphibians and macroinvertebrates are adept overland dispersers – though they may be sensitive to top-down control by fishes. To better understand these phenomena, I sampled 10-20 wetlands each at nine regions in North and South America for fish, amphibians and macroinvertebrates. With these wetlands I sought to determine how fishes colonized GIW habitats despite being dispersal limited and what effect fishes had on the amphibians and macroinvertebrates in wetlands. To further explore fish effects on prey, and to determine the effect of specific fish species on amphibians and macroinvertebrates, I constructed 21 in-ground mesocosms and inoculated 7 of these with Eastern Mosquitofish, 7 with Eastern Mosquitofish and Warmouth, and left 7 fishless. Finally, I examined a subset of my wetlands in southern Florida to analyze changes in fish occupancy over time and the downstream effects of occupancy change on amphibians. Across the regions I sampled, fish occupancy in wetlands correlated to landscape variables (landscape heterogeneity, distance to the nearest fish-dominated wetland, wetland size), and in turn fish changed assemblage structure at all the regions. This latter result mirrored the results from the mesocosms, except that the 7 mesocosms with Warmouth and Eastern Mosquitofish were different from the other two treatments, and the fishless and Eastern Mosquitofish inoculated mesocosms were similar to one another. At the site in southern Florida, fish were extirpated from some wetlands, and recolonized others. Overall 46% of wetlands changed their fish status. The results of this dissertation demonstrate that fish across my diverse study regions mostly colonize other wetlands across the landscape through flooding events, and this result has profound implications to the conservation of amphibians and macroinvertebrates. Specifically, wetland creation and restoration should be undertaken with the knowledge that fish are likely to colonize a site if there is even temporary landscape-facilitated connectivity with a fish refuge, and land managers should keep in mind dynamic fish occupancy in some wetlands when contributing to imperiled species management.
Recommended Citation
Holbrook, Joshua, "Drivers of Faunal Communities in Isolated Wetlands: Local and Landscape Determinants of Assemblages" (2025). All Dissertations. 4181.
https://open.clemson.edu/all_dissertations/4181
Author ORCID Identifier
0009-0006-9062-4563