Thesis (M.S.)--Missouri State University, 2008. / "August 2008." Includes bibliographical references (leaves 70-81). Also available online.

Thesis (M.Sc.). / Written for the Dept. of Biology. Title from title page of PDF (viewed 2009/06/25). Includes bibliographical references.

Amphibian populations around the world have been declining rapidly over the past two decades, particularly in upland regions of the neotropics, where a fungal pathogen that causes chytridiomycosis has decimated many regions. Despite increasing concern over these and other dramatic losses of biodiversity, little information is available on the overall ecological effects of amphibian declines. As part of the Tropical Amphibian Declines in Streams (TADS) project, I quantified major energy fluxes, secondary production, and macroinvertebrate community structure for two consecutive years in four stream reaches in the Panamanian uplands, two with healthy amphibian populations and two that had experienced amphibian declines in 1996-1997. Despite relatively high year-round inputs of allochthonous organic materials, storage of detritus in the stream channels was low compared to streams in temperate regions. Organic matter inputs and standing stocks were similar between pre- and post-decline streams, and did not differ appreciably with season. Seston export was a major energetic flux in these systems, and differences in the nutritional quality (C:N) of seston in pre- and post-decline streams suggested that the loss of tadpoles may decrease the quality of materials exported from these headwaters. At coarse scales (e.g., total abundance) macroinvertebrate assemblages were similar between pre- and post-decline sites, but there were noticeable differences in production and functional and taxonomic structure. Pre-decline reaches had higher shredder production and post-decline streams had higher scraper production. In addition, taxonomic differences between pre- and post-decline streams were also evident, with a shift from dominance of smaller scraper taxa in pre-decline sites (i.e. Psephenus) to larger-bodied scrapers such as Petrophila in post-decline reaches. Filterer production was dominated by hydropsychid caddisflies in pre-decline reaches, whereas black flies dominated filterer production in post-decline reaches. Overall, detritus and detritivores dominated energy flow in all study reaches. However, scrapers were well represented in these systems and appeared to be food-limited, particularly in pre-decline reaches where grazing tadpoles were still abundant. During the second year of my study, predicted amphibian declines began at the pre-decline site. The loss of amphibians through this year resulted in subtle shifts in macroinvertebrate functional and taxonomic structure, which correlated with changes in available food resources. Some grazing mayflies responded positively to declining tadpole populations and subsequent increased periphyton resources, suggesting a potential for some degree of functional redundancy in these systems. However, other grazers, such as the water penny beetle Psephenus, showed no response during the period of study. My results indicate that responses of remaining consumers to tadpole declines in streams may not be evident at some coarse scales (e.g., total abundance, biomass). However, differences in secondary production at the community and the functional level, along with assemblage structure changes were evident, with some individual taxa responding relatively quickly. Long-term studies in these same stream reaches will further illuminate the ultimate ecological consequences of these dramatic and sudden losses of consumer diversity.

Humans are modifying the global landscape at an unprecedented scale and pace. As a result, species are declining and going extinct at an alarming rate. Here, I investigate two main aspects of species’ declines: what factors are contributing to their declines and how effective our conservation efforts have been. I assessed one of the main mechanisms for protecting species by looking at the Endangered Species Act (ESA) in the United States. I examined three separate indicators of species declines for different groups of species: range contractions in Canadian imperilled species, declines in abundance in global amphibian populations and increases in temporal variability in abundance in North American breeding birds. I found that change in recovery status of ESA listed species was only very weakly related to the number of years listed, number of years with a recovery plan, and funding. These tools combined explained very little of the variation in recovery status among species. Either these tools are not very effective in promoting species’ recovery, or species recovery data are so poor that it is impossible to tell whether the tools are effective or not. I examined patterns of species’ declines in three different groups in relation to a number of anthropogenic variables. I found high losses of Canadian imperiled bird, mammal, amphibian and reptile species in regions with high proportions of agricultural land cover. However, losses of imperiled species are significantly more strongly related to the proportion of the region treated with agricultural pesticides. This is consistent with the hypothesis that agricultural pesticide use, or something strongly collinear with it (perhaps intensive agriculture more generally), has contributed significantly to the decline of imperiled species in Canada. Global increases in UV radiation do not appear to be a major cause of amphibian population declines. At individual sites, temporal changes in amphibian abundance are not predictably related to changes in UV intensity. Variability in species’ abundance of North American breeding birds, after accounting for mean abundance, is not systematically higher in areas of high human-dominated land cover or climate change. Rather, it appears that areas with a high proportion of human-dominated cover come to have a higher proportion of highly abundant, and thus more variable, species.

Humans are modifying the global landscape at an unprecedented scale and pace. As a result, species are declining and going extinct at an alarming rate. Here, I investigate two main aspects of species’ declines: what factors are contributing to their declines and how effective our conservation efforts have been. I assessed one of the main mechanisms for protecting species by looking at the Endangered Species Act (ESA) in the United States. I examined three separate indicators of species declines for different groups of species: range contractions in Canadian imperilled species, declines in abundance in global amphibian populations and increases in temporal variability in abundance in North American breeding birds. I found that change in recovery status of ESA listed species was only very weakly related to the number of years listed, number of years with a recovery plan, and funding. These tools combined explained very little of the variation in recovery status among species. Either these tools are not very effective in promoting species’ recovery, or species recovery data are so poor that it is impossible to tell whether the tools are effective or not. I examined patterns of species’ declines in three different groups in relation to a number of anthropogenic variables. I found high losses of Canadian imperiled bird, mammal, amphibian and reptile species in regions with high proportions of agricultural land cover. However, losses of imperiled species are significantly more strongly related to the proportion of the region treated with agricultural pesticides. This is consistent with the hypothesis that agricultural pesticide use, or something strongly collinear with it (perhaps intensive agriculture more generally), has contributed significantly to the decline of imperiled species in Canada. Global increases in UV radiation do not appear to be a major cause of amphibian population declines. At individual sites, temporal changes in amphibian abundance are not predictably related to changes in UV intensity. Variability in species’ abundance of North American breeding birds, after accounting for mean abundance, is not systematically higher in areas of high human-dominated land cover or climate change. Rather, it appears that areas with a high proportion of human-dominated cover come to have a higher proportion of highly abundant, and thus more variable, species.

Humans are modifying the global landscape at an unprecedented scale and pace. As a result, species are declining and going extinct at an alarming rate. Here, I investigate two main aspects of species’ declines: what factors are contributing to their declines and how effective our conservation efforts have been. I assessed one of the main mechanisms for protecting species by looking at the Endangered Species Act (ESA) in the United States. I examined three separate indicators of species declines for different groups of species: range contractions in Canadian imperilled species, declines in abundance in global amphibian populations and increases in temporal variability in abundance in North American breeding birds. I found that change in recovery status of ESA listed species was only very weakly related to the number of years listed, number of years with a recovery plan, and funding. These tools combined explained very little of the variation in recovery status among species. Either these tools are not very effective in promoting species’ recovery, or species recovery data are so poor that it is impossible to tell whether the tools are effective or not. I examined patterns of species’ declines in three different groups in relation to a number of anthropogenic variables. I found high losses of Canadian imperiled bird, mammal, amphibian and reptile species in regions with high proportions of agricultural land cover. However, losses of imperiled species are significantly more strongly related to the proportion of the region treated with agricultural pesticides. This is consistent with the hypothesis that agricultural pesticide use, or something strongly collinear with it (perhaps intensive agriculture more generally), has contributed significantly to the decline of imperiled species in Canada. Global increases in UV radiation do not appear to be a major cause of amphibian population declines. At individual sites, temporal changes in amphibian abundance are not predictably related to changes in UV intensity. Variability in species’ abundance of North American breeding birds, after accounting for mean abundance, is not systematically higher in areas of high human-dominated land cover or climate change. Rather, it appears that areas with a high proportion of human-dominated cover come to have a higher proportion of highly abundant, and thus more variable, species.

Coral reef declines, particularly in coastal zones, have been linked to thermal stress and anthropogenic impacts on water quality. St. Lucie Reef near Stuart, Florida receives increased estuarine efflux as a result of watershed changes and management policies that have substantially altered historic, natural flows. This research used ambient and elevated temperatures (25°C and 30°C, respectively), and offshore versus St. Lucie Estuarine discharge water to investigate the individual and interactive effects of thermal and water quality stress on Montastraea cavernosa, a dominant scleractinian coral species at St. Lucie Reef. These goals were accomplished using ex-situ, factorial, experimental design that was supplemented with existing in-situ monitoring on St. Lucie Reef. Zooxanthellae density and chlorophyll content were evaluated to determine effects on the corals and their symbionts. Zooxanthellae populations were significantly affected by thermal stress. Significant interactions between temperature and water treatment were observed, suggesting that the impacts of discharge water may be supplanted when corals are exposed to thermal stress. In a supplement to the experiment, M. cavernosa colonies transplanted from Palm Beach to St. Lucie Reef demonstrated resilience despite exposure to more variable environmental conditions. Collaborative partnerships with multiple state agencies and local government offices facilitated data sharing to inform decision making for South Florida’s resource management strategies. Creating effective resource management is crucial for the conservation of coastal ecosystems impacted by land-based sources of pollution both locally and globally. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Thesis (M.S.)--Texas State University-San Marcos, 2008. / Vita. Appendix: leaves 73-89. Includes bibliographical references (leaves 90-93). Also available on microfilm.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.