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 (PhDEnvironmentalManagement)--University of South Australia, 2004.

Over the relatively short period since European settlement in the 1830’s, the Mount Lofty Ranges (MLR) in South Australia have suffered a precipitous decline of natural habitat. The effects of habitat fragmentation on the herpetofauna of the southern MLR were investigated in a series of forest remnants and provide the thematic background of this thesis which focuses on five separate but thematically interconnected aspects of habitat fragmentation that are presented in separate, semi-autonomous chapters (3-7). / The study confirmed that the original herpetofauna still persists in the southern MLR. Habitat fragmentation apparently did not affect the species richness of the region. However, there are important differences in the occurrences of individual species across the archipelago of forest remnants. The distribution patterns of the herpetofauna in forest remnants of the southern MLR are not random but highly nested. As a consequence of a significant association of species richness with the area, it appears that the proportion of the original forest-dependent reptiles of the MLR that can be preserved in habitat fragments is a direct function of the remnant size. The processes responsible for the observed deterministic extinction patterns appear to be habitat loss and habitat fragmentation. Contrary to many forest-dependent reptiles, most amphibian species are still widespread at the investigated scale and generally appear to be less affected by the effects of forest loss and forest fragmentation in the MLR. / Actual habitat remnancy in the southern MLR is below 13% and with 97.6% of all forest fragments smaller than 100ha, many of the most area-sensitive f orest-dependent reptiles survive in just a handful of remnants that are large enough to support viable populations. Although smaller remnants still support some forest- dependent reptiles, their herpetofauna is generally greatly impoverished. While abundances of most species were too low to estimate expected recapture values in dispersal experiments, crossings of common anthropogenic boundaries by local reptiles appear to be rare events. Where expected recapture values could be estimated, such as for L. guichenoti in a case study, most boundaries did appear to show a filter effect. Differences existed among species and communities in regard to boundary permeability. The results suggest that the extensive road network in the southern MLR, through filter effects (i.e. road mortality) and barrier effects (i.e. edge avoidance), is likely to decrease landscape connectivity. The study further demonstrated the existence of significant edge effects on reptiles. Such edge effects are expected to have a particularly large impact on populations of smaller forest fragments that are mostly or completely ecotonal and, consequently, harbour mostly edge-tolerant forest species and habitat generalists. / The above-mentioned case study of Lampropholis guichenoti demonstrated that this ubiquitous species is naturally abundant not only under relatively pristine conditions, but also in disturbed habitat. The species apparently possesses a variety of biological, ecological and behavioural traits, such as a high degree of ecological plasticity, non-territoriality and klepto-parasitic behaviour that may explain its relatively successful survival in the face of extensive habitat fragmentation in the southern Mount Lofty Ranges. / Findings of this study have clear implications for conservation and restoration planning. Nested subset analysis emerged as a useful analytical tool to identify potential focal species that could serve in the development of a taxon-based surrogate scheme. This multi-species approach could be a simple and cost-effective way to address regional conservation problems when time and resources are limited. A focal-species approach using forest dependent reptiles in a surrogate scheme appears particularly useful for herpetofaunal diversity conservation in forest remnants of the MLR. / Thesis (PhD)--University of South Australia, 2004.

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

Thesis (M.S.)--Rutgers University, 2010. / "Graduate Program in Ecology and Evolution." Includes bibliographical references (p. 55-57).

Thesis (MSc. (Veterinary Tropical Diseases))--University of Pretoria, 1999. / Also available in print format.

Thesis (Ph.D.) - University of Queensland, 2004. / Card in pocket at front. Includes bibliography.

Thesis (M. Sc.)--University of Alberta, 1997. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Renewable Resources. Also available on the World Wide Web.

1. Convoluta roscoffensis is an intertidel flatworm symbiotic with the green alga, Platymonas convolutae. Field studies of a population of Convoluta on Shell Beach, Herm, Channel Islands, involved the measurement of seasonal changes in numbers of Convoluta and in environmental conditions. Features of the habitat were measured, including the nutrient levels in the beach run-off water flowing over Convoluta colonies and the light energy available. 2. The position of the colonies on the beach meant that they received about 60% of available PAR (photosynthetically active radiation) i.e. 4883 E m-2 in 1977. The spacing of worms in the colonies (mean density 9.3 x 10 to the power 5 worms m-2) was such that they did not haye to shade each other. 3. Nutrient analyses revealed that the beach run-off water is rich in nutrients, and dominated by nitrate (mean concentration 6-16υg atoms N03-N 1to the power -1). Uptake of nutrients from the run-off water by Convoluta was not apparent. 4. The Convoluta population was most abundant in September and numbers were lowest in May and June. This pattern of fluctuation in numbers showed some relation to seasonal changes in light intensity but not to changes in nutrient levels. 5. Primary productivity measurements (using the 14C technique) of symbiotic and free-living Platymonas showed that both types of algae achieved assimilation numbers (mg carbon fixed (mg chlorophyll 'a')-1 h-1) which were in the range 1-3. Photosynthetic rate was higher in worms incubated in Herm run-off water than in offshore seawater. Comparisons between symbiotic and free-living Platymonas were made with respect to photoinhibiting light levels and the amounts of dark carbon fixation. 6. Extrapolation of primary productivity values to Convoluta in the field gave an estimated annual production of 872.9 g carbon m to the power -2 of colony for 1977. This is comparable with values for rich ocean waters and coral reefs. 7. Primary production measurements were also made on a tropical algal-invertebrate system, Zoanthus sociatus, at Discovery Bay, Jamaica. The oxygen technique was used, so the values of assimilation number were not directly comparable with those obtained for Convoluta, but the symbionts of Zoanthus (Gymnodinium microadriaticum) achieved assimilation numbers similar to those published for other free-living species of Gymnodinium. The symbionts isolated from Zoanthus were of similar size to and contained similar amounts of chlorophyll 'a' to the Platymonas symbionts of Convoluta. 8. Structural studies of the development of symbiosis in Convoluta showed that the host and symbiont are in very intimate contact. There was evidence for the controlled and integrated growth of host and symbiont in the distribution and orientation of the 20,000-70,000 algae inside Convoluta. The ratios of algal to host protein and cell volume were measured and compared with values for other algal-invertebrate systems to discover whether any general statements may be made regarding the proportions of algal to host tissue in established symbioses.

The northern leopard frog (Rana pipiens) is a species that depends on landscape connectivity to complete its lifecycle. However, due to historic and present anthropogenic landscape changes, this species encounters a variety of agriculture fields during migratory and dispersal movements. These landscape changes have potential to affect habitat connectivity for these frogs and may interfere with the species? life-cycle needs. Differing land-cover types have varying effects on movement, desiccation and predation of the northern leopard frog, which in turn affect the frog?s ability to survive. Through creation and use of an agent-based model that can simulate individual frog movement on a modeled landscape, I explored habitat connectivity in the prairie-pothole region. I used northern leopard frog movement and desiccation data collected from two summers of field work to inform my modeled scenarios. The model I developed allows for the exploration of habitat connectivity under various patterns of land-cover change. / U.S. Geological Survey Climate Research and Development Program / North Dakota State University (NDSU)