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Elton (1927) realized that, intuitively at least, nature was complex and stable. And that the last property contributed to the first. This idea was challenged mathematically by Gardner and Ashby (1970) and May (1972), and in the years following various models have attempted to reconcile these opposing views. Unlike previous mathematical approaches that demonstrated that simple stable systems are destabilized through added complexity, the approach presented herein began with a model that was unstable. This perspective provided allows model complexity and at the same time increased likelihood of mathematically stable. This novel observation suggested that ecosystem complication might stabilize a community. Within these models a system may be stable despite the coexistence of several competitors, in direct opposition to the Competitive Exclusion Principle. The hypothesis that the principle may not hold as an absolute generality beyond two competitors is proposed. This paradox may be explained by (1) interactions between competitors, (2) a keystone predator, or (3) a combination of the first two factors. / Graduation date: 1999

Insights gained from metapopulation and metacommunity biology indicate that the connectivity of subpopulations and communities by species dispersal can profoundly impact population dynamics, community structure, and ecosystem attributes. Recent advancements in metacommunity theory further suggest that the rate of species dispersal among local communities can be important in altering local and regional species richness and ecosystem functioning. The role of species dispersal rates relative to patch-type heterogeneity and associated intrinsic community structuring mechanisms (competition, predation) in affecting diversity of multi-trophic communities, however, remains unknown. Here, I address the relative influence of regional and local processes in altering species richness and ecosystem functioning at multiple spatial scales in freshwater pond metacommunities. In a series of experiments, I employed pond mesocosm metacommunities to manipulate planktonic species dispersal rates and the incidence of top predators which differed in prey selectivity. The consequences of dispersal and predation to zooplankton species richness, trophic structure, ecosystem stability, and prey traits were evaluated. Generally, my findings support predictions from metacommunity models, and demonstrate that dispersal strongly affects community and ecosystem-level properties. In accord with dispersal-diversity theory, dispersal rate affected species richness and ecosystem stability at multiple spatial scales. The presence, but not the rate, of dispersal had strong effects on the partitioning of biomass amongst producers, grazers, and top predators. The relative influence of predation on local and metacommunity structure varied across experiments and largely depended upon predator identity and the degree of feeding specialization. The research presented herein is some of the first work to evaluate how species dispersal rates can affect dispersal-diversity relationships, diversity-stability relationships, trophic structure, and the distribution of prey traits in metacommunities. In addition to advancing ecological theory, the results have important implications for conservation as fragmented landscapes become increasingly prevalent, and local and regional biotas modified. Ultimately, it proves critical to identify drivers of local and regional species richness in order to maintain biotic integrity at the global scale. / text

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on July 31, 2009). "Department of Entomology." Includes bibliographical references.

Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed April 14, 2010). Advisor: Mark W. Kershner. Keywords: biodiversity; nitrogen; fertilization; plant litter; trophic dynamics; epigeal community. Includes bibliographical references.

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 167-174).

An estimated 39 million m3 of timber was damaged across the Southeast Forest District of Mississippi due to Hurricane Katrina. Aggregated forest plot-level biometrics was coupled with wind, topographical, and soil attributes using a GIS. Data mining through Regression Tree Analysis (RTA) was used to determine factors contributing to shear damage of pines and wind-throw damage of hardwoods. Results depict Lorey’s Mean Height (LMH) and Quadratic Mean Diameter (QMD) are important variables in determining the percentage of trees and basal area damaged for both forest classes with sustained wind speed important for wind-throw and peak wind gusts for shear. Logistic regression based on stand damage classification compared to RTA revealed LMH, stand height to diameter ratio, and sustained wind variable concurrence. Reclassification of MIFI plot damage calls based on percentage of trees damaged increased predictability of wind-throw and shear classification. This research can potentially aid emergency and forest managers for better mitigation and recovery decisions following a hurricane.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013. / Species richness and estimates of species richness were calculated based on assemblages of bats, within the biomes of South Africa, Lesotho and Swaziland following the vegetation classification of Mucina and Rutherford (2006). Similarity indices were used to explore the various relationships between the assemblages between the various biomes. Taxonomic diversity and distinctness examined the various assemblages within each of the biomes to investigate which biomes contained assemblages that were taxonomically diverse and/or taxonomically distinct compared to all species known to occur within South Africa, Lesotho and Swaziland. The Desert biome had the lowest recorded species richness (5 species), and there was insufficient data to calculate estimates of species richness for this biome. While the Albany had 11 species recorded with species estimates (Est.) ranging between 11-12, then in increasing order - Nama-Karoo (12 species, Est. 13-25 species), Succulent-Karoo (13 species, Est. 15-30 species), Fynbos (17 species, Est. 18-25 species), Indian Ocean Coastal Belt (31 species, Est. 32-36 species), Forest (32 species, Est. 37-46 species), Grassland (39 species, Est. 42-54 species), Azonal (45 species, Est. 49-63 species) and Savanna (57 species, Est. 59-67 species). The mean recorded estimates (based on the averages of all models) and rounding up to a full species indicates that the Albany biome contains the lowest expected species richness of 12 species, then Fynbos and Nama-Karoo (21 species), Succulent-Karoo (22 species), Indian Ocean Coastal Belt (34 species), Forest (43 species), Grassland (49 species), Azonal (54 species) and Savanna (64 species). Sample completeness was calculated for each of the biomes which indicates in ascending order that the Albany biome is 93.2% complete followed by the Indian Ocean Coastal Belt biome (91.1%), Savanna biome (89.9%), Azonal biome (84.1%), Fynbos biome (81.5%), Grassland biome (80.7%), Forest biome (75.8%), Succulent-Karoo biome (61.3%), and Nama-Karoo biome (59.9%). This showed that the Albany biome was found to be the only biome that has been sufficiently sampled. The Jaccard and Sørensen pair wise indices resulted in the clustering of the biomes with similar species richness, due to the large range in species richness (5-57 species) between the biomes. The Lennon et al. (2001) index which is not affected by large species richness between the samples indicated that the Desert and Nama-Karoo assemblages were most dissimilar to one another, while the Indian Ocean Coastal Belt assemblage was the most similar to the remaining biome assemblages. The Albany biome assemblage and Azonal biome assemblage were shown to the most dissimilar to one another. The Grassland, Nama-Karoo and Savanna biomes contribute to higher taxonomic diversity, while the Albany, Azonal, Fynbos, Nama-Karoo and Succulent-Karoo biomes contain lower species richness generally but represent a higher taxonomic distinctness from the chiroptera assemblages in the Grassland and Savanna biomes. The Desert, Forest and Indian Ocean Coastal Belt biomes do not iv contain bat assemblages that are neither taxonomically distinct nor diverse when compared to the taxa of South Africa, Lesotho and Swaziland. The bat assemblage within the Nama-Karoo are both taxonomically diverse and distinct from chiroptera assemblages found within the other nine biomes, requiring a greater focus on conservation actions for the bat species assemblage located within this biome.