Date of Award
M'Closkey, Robert T.,
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Ecological investigations have traditionally focused on local scales and have been of short duration. The importance of scale to perception of patterns in nature is now recognized, and there is increased interest in determining the relative roles of local versus regional, and contemporary versus historical processes in structuring populations and communities. Over three years I surveyed 180 southwestern Ontario ponds to record amphibian presence and measure habitat and landscape variables. My goal was to document and explain patterns of amphibian species richness and incidence, and to investigate how these patterns change spatially and temporally. Species richness and incidence differed significantly among regions and were associated with a combination of both local and regional variables. However, the amount of regional woodlands accounted for most of the variance. Water chemistry played only a minor role in affecting species richness and distribution; however, laboratory studies revealed toxic effects of nitrates at realistic field concentrations. Species richness was significantly lower at predatory fish ponds compared to other ponds. Amphibians having large bodies or clutch sizes, or anti-predator defenses, co-occurred with fish more frequently than small species. Introduced fish produced large-scale patterns through their effect on local assemblages. Local extinction of bullfrogs was correlated with increased relative abundance of its intraguild prey, the green frog. The entire fauna showed nested subset structure. Species that require woodlands and those vulnerable to fish predation showed the highest degree of nestedness. Incidence was positively correlated with species-specific dispersal capabilities. The system is characterized by high species turnover which has resulted in trends of both increased and decreased species incidence. Green frog occupancy, abundance, and turnover was both scale and location dependent, extinctions occurred only at the local scale, and small populations were vulnerable. I developed habitat quality models for use in conservation. Incidence and duration of site occupancy were positively related to habitat quality. In this system fish predation, a contemporary local process, and historical regional deforestation appear to be the dominant processes affecting amphibian communities. Large-scale perspectives are necessary to explain the patterns in amphibian communities and to assess the status of species.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .H42. Source: Dissertation Abstracts International, Volume: 59-08, Section: B, page: 3846. Adviser: Robert T. M'Closkey. Thesis (Ph.D.)--University of Windsor (Canada), 1997.
Hecnar, Stephen Joseph., "Species richness, species turnover, and spatial dynamics of amphibian communities." (1997). Electronic Theses and Dissertations. 3554.