Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (p. 137-154). Also available via the World Wide Web.

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Laboratory experiments have suggested that the coexistence of certain heteromyid rodent species is facilitated through differential use of seed dispersions (clump sizes). Field experiments with the Bannertail kangaroo rat, Dipodomys spectabilis, and Merriam's kangaroo rat, D. merriami, indicate their use of different clump sizes is not sufficiently specialized to permit coexistence. Field experiments based on the assumption that these species interact primarily through aggression demonstrated that during at least one season of the year D. spectabilis excludes the smaller D. merriami from its foraging range. Preliminary characterization of spatial heterogeneity of resource productivity implies that the competitive coexistence of these species is regional and is dependent upon the existence of areas with low productivity that are not economically usable by D. spectabilis. These areas of low productivity may serve as a competitive refuge for D. merriami, facilitating its persistence. A brief review of the evidence for the occurrence of competition between heteromyid species is presented, as is a selected review of the evidence supporting the various hypotheses explaining the competitive coexistence of heteromyid rodents.

Goldfish, an exotic originally from Asia, are frequently released into North American waters, causing unknown impacts on native fauna and flora. In the wild, diet overlap between feral goldfish (Carassius auratus) and native red-spotted newts (Notophthalmus v. viridescens) is high, leading to potential interspecific competition over food. In the laboratory, we manipulated densities of goldfish and red-spotted newts to test competition for benthic food organisms between these unrelated species. / No intraspecific interference was noted for either goldfish or newts at any density. However, as density increased food resources were more rapidly depleted by both species, suggesting scramble competition. Foraging strategies of the species differed. Goldfish shoaled more and abandoned food patches before they were depleted, whereas newts were solitary and exhausted a food patch before moving on to new sites. Both species found more food patches when with heterospecifics than with conspecifics, suggesting interspecific information transfer. In addition, goldfish found more food patches than newts in all trials, indicating scramble competition occurred.

We use metapopulation models based on a classic competition-colonization trade-off in order to (1) study community responses to spatially structured habitat loss on dynamic landscapes when species are assembled by ecological (biogeographic) processes; and (2) to study how species are assembled into communities by evolutionary mechanisms. In the first part of our study we show how the response of species richness to habitat destruction in dynamic landscapes can be driven by the existence of either the spatial structure of habitat dynamics or by life-history trade-offs among species. In the second part of our study we confirm that competitive trade-off models predict runaway evolution towards stochastic extinction, making it impossible for stable multispecies assemblages to evolve. We demonstrate that by relaxing the strict deterministic nature of competitive exclusion in such models species can avoid selection towards extinction, allowing for the possibility of species co-evolution resulting in stable multispecies assemblages.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--University of Adelaide, Dept. of Soil Science, 1996. / Copy of author's previously published work inserted. Includes bibliographical references (leaves 261-306).

Thesis (M.S.)--Georgia Southern University, 2008. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Directed by Bruce A. Schulte. ETD. Includes bibliographical references (p. 69-88) and appendices.