Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 24-34)

Thesis (Ph.D.(Zoology)) -- University of Pretoria, 2001. / Abstract in English. Includes bibliographical references.

This work explores the effect of diversity of individuals on a community. The mechanisms generating diversity are explored, their effects on patterns of diversity are examined, and the impact of diversity on community properties (such as productivity and stability) is investigated. Three individual-based models are employed: 1) a meanfield differential equation model, 2) a simulation model of plant populations, and 3) a simulation model of interacting organisms. The mean-field model is used to show that the traits of individuals in a community affect community diversity. The mathematical analysis, supported by numerical simulations, demonstrates that trade-offs between the individual traits are required for community diversity to exist. Moreover, the form of the trade-offs defines the equilibrium distribution of the population over the trait values. The nature of interactions among individuals (in particular, competition) determines the stability of the equilibrium state. For a more realistic representation of the community, a more detailed and spatially explicit model of a community is defined. This model simulates each individual explicitly, with a fuller description of the physiological traits and interactions. The model is parameterised using experimental data from a grassland species <i>R. acetosa</i>. Diversity patterns in the modelled communities are of the same form as the patterns observed in biological communities. The mechanisms generating diversity patterns are examined. As in the mean-field model, analysis of the simulation model shows that a trade-off between physiological traits is responsible for generation of diversity in the simulation model also. Moreover, it affects the form of the diversity patterns. Community productivity results from the interplay of community diversity and environmental conditions. To further explore the effect of individual interactions on community diversity and stability, a model of interacting organisms is developed. This model is a modification of the plant model, with the possibility of two-way mutualistic interactions between organisms. The mutualistic interactions are found to increase community diversity in space and time and to promote community stability under environmental disturbance. The impact of individual-scale processes on community-scale dynamics has recently been recognised as an important factor contributing to ecosystem dynamics. This work defines and explores some of the links between individual and community scales within ecological communities. In particular, it shows that individual traits in a community can affect community- scale properties such as diversity patterns and productivity, while individual interactions are important for community diversity and stability.

published_or_final_version / abstract / toc / Comparative Asian Studies / Master / Master of Arts

Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 98-112)

Thesis (M.App.Sc.) -- University of Adelaide, Dept. of Applied and Molecular Ecology, 2000. / Bibliography: leaves 107-117.

Soil biodiversity is an often overlooked component of global biodiversity, despite being important for supporting soil ecosystem services, notably decomposition processes. As the UK becomes increasingly urbanised, knowledge is required to help gardeners maximise urban green space resources for biodiversity. It is often assumed that non native vegetation has negative impacts on biodiversity, however, this hypothesis has not been tested for soil biodiversity. The overarching aims were to establish whether the geographical origin of vegetation affected soil faunal assemblages and decomposition rates for a UK soil. Traditional taxonomic methods and a molecular phylogenetic approach were used to characterise the Collembola communities of plots planted with vegetation from three geographical regions: ‘Native’, ‘Near native’ and ‘Exotic’. For comparison, additional soil cores were collected from the amenity grassland sites adjacent to the experimental plots, a lowland heath and a semi-natural woodland. No difference was found either in terms of the taxonomic diversity (1-D & H’) or phylogenetic diversity (PD & MPD) for the Collembola, under the different vegetation treatments, although differences in abundance were observed for some taxa (Acari & Collembola). Decomposition rates were assessed for each plot, using both twig (B. pendula) and leaf (Q. robur) litter bags for the soil mesofauna and bait lamina strips for earthworm activity; none of these parameters showed evidence of a vegetation origin effect on decomposition processes. The greatest differences were found when all sites were considered, with distinct Collembola communities found at each of the habitats; the semi-natural habitats had greater Collembola species diversity than the experimental plots, however, the decomposition rates of the latter were significantly higher. The implications of all results have been discussed with regards to the management of gardens for soil biodiversity, reaching the conclusion that vegetation origin is not of paramount importance.

Grassland communities represent major biodiversity hotspots across the United States. Among these grassland types is the short-leaf pine savanna, a major historical habitat along the Cumberland Plateau. The Cumberland Plateau’s grasslands are under threat due to land use changes such as urbanization and land conversion to pasture and hardwood forests. This study seeks to better understand the community ecology of ants on the Cumberland Plateau using powerlines as a comparison to degraded and historic habitats. Ants have a preference between open sites and forested sites, a separation of 44.5% on a DCA. The Simpson diversity places the short-leaf pine savanna significantly lower than adjacent forest, (df-3, F=3.56, p-value=0.029; Figure 1.5). Stenamma Westwood, 1839 is a cryptic genus with a Holarctic clade of 44 species, six of which occur in the southeastern United States. This work is a redescription providing an updated key, with images to those species in the southeast.

No description available.

No description available.