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Selection in spatially heterogeneous environments is a convenient explanation for the high levels of genetic variation observed in natural populations. Indeed, theoretical studies predict that spatial heterogeneity leads to higher levels of variation in a variety of selection models. These models, however, have assumed quite restrictive parameters (e.g., two alleles, fixed gene flow and specific selection schemes). Therefore, the effect on spatial heterogeneity is still poorly understood for a wider range of parameters (e.g., multiple alleles, different levels of gene flow and more general selection schemes). We have relaxed some of the assumptions that have limited the previous models and studied the effect of spatial heterogeneity using simple single-locus viability selection models. First, we investigate the rarity of the parts of fitness space maintaining variation for multiple alleles and different levels of gene flow by randomly sampling that space using a "fitness space" approach. The volume of fitness space maintaining variation is always larger in a spatial model compared to a single-population model regardless of gene flow. Moreover, this volume is relatively larger for higher numbers of alleles, indicating that spatial heterogeneity is more efficient maintaining higher levels of variation. Second, we investigate the ease with which a more natural process of recurrent mutation and selection evolves to the particular area of fitness space maintaining variation using a "construction" approach. Depending on the amount of gene flow, the construction approach leads to both higher and lower levels of variation compared to a single-population model. Thus, spatial heterogeneity can both constrain and promote the ease with which a natural process of mutation and selection evolves to maintain variation. Also, the construction approach results in variation being maintained in a more stable subset of the volume of fitness space than the volume that resulted from the fitness space approach. Third, we investigate the effect of higher and lower levels of spatial environmental heterogeneity using the construction approach. The different levels of heterogeneity and gene flow interact to influence the amount of variation that is eventually maintained and this interaction effect is especially strong for intermediate levels of gene flow. More heterogeneous environments can maintain higher levels of variation, but selection in these environments also results in a higher level of migration load, lowering the final amount of adaptation that is achieved by the simulated evolutionary process. Finally, we investigate effect of genetic drift and finite populations using the construction approach. Interestingly, two different effects emerge for smaller and larger populations; in smaller populations genetic drift lowers the amount of variation as expected, whereas, more surprisingly, genetic drift increases the amount of variation in larger populations. Overall, spatial heterogeneity has profound effects on the outcome of selection, resulting in elevated levels of genetic variation for a wide variety of parameters.

Recently the independent multinomial selections model (IMS) with the multinomial logit link has been suggested as an analysis tool for radio-telemetry habitat selection data. This model assumes independence between animals, independence between sightings within an animal, and identical multinomial habitat selection probabilities for all animals. We propose two generalizations to the IMS model. The first generalization is to allow a Markov chain dependence between consecutive sightings of the same animal. This generalization allows for both positive correlation (individuals persisting in the same habitat class in which they were previously sighted) and negative correlation (individual vacating the habitat class in which they were previously sighted). The second generalization is to allow for heterogeneity. Here, a hierarchical Dirichlet-multinomial distribution is used to allow for variability in selection probabilities between animals. This generalization accounts for over-dispersion of selection probabilities and allows for inference to the population of animals, assuming that the animals studied constitute a random sample from that population.. Both generalizations are one parameter extensions to the multinomial logit model and allow for testing the assumptions of identical multinomial selection probabilities and independence. These tests are performed using the score, Wald, and asymptotic likelihood ratio statistics. Estimates of model parameters are obtained using maximum likelihood techniques, and habitat characteristics are tested using drop-in-deviance statistics. Using example data, we show that persistence and heterogeneity exist in habitat selection data and illustrate the difference in analysis results between the IMS model and the persistence and heterogeneity models. Through simulation, we show that analyzing persistence data assuming independence between sightings within an animal gives liberal tests of significance for habitat characteristics when the data are generated with positive correlation and conservative tests of significance when the data are generated with negative correlation. Similarly, we show that analyzing heterogeneous data, assuming identical multinomial selection probabilities, gives liberal tests of significance for habitat characteristics. / Graduation date: 2001

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 50-55). Also available on the World Wide Web.

Habitat fragmentation is a fundamental process that determines trends and patterns of distribution and density of organisms. These patterns and trends have been the focus of numerous terrestrial and marine studies and have led to the development of several explanatory hypotheses. Systems and organisms are dynamic and no single hypothesis has adequately accounted for these observed trends. It is therefore important to understand the interaction of these processes and patterns to explain the mechanisms controlling population dynamics. The main aim of this thesis was to test the effect of patch size and isolation on organisms with different modes of dispersal. Mode of dispersal has previously been examined as a factor influencing the effects that habitat fragmentation has on organisms. Very few studies have, however, examined the mode of dispersal of marine organisms because it has long been assumed that marine animals are not directly influenced by habitat fragmentation because of large-scale dispersal. I used two co-occurring species of siphonariid limpets with different modes of dispersal to highlight that not only are marine organisms affected by habitat fragmentation but that they are affected in different ways. The two species of limpet, Siphonaria serrata and Siphonaria concinna, are found within the same habitat and have the same geographic range along the South African coastline, however, they have different modes of dispersal and development. The effect of patch size on organism density has been examined to a great extent with varied results. This study investigated whether habitat patch size played a key role in determining population density and limpet body sizes. The two species are found on the eastern and southern coasts of South Africa were examined across this entire biogeographic range. Patch size was found to have a significant effect on population density of the pelagic developer, S. concinna, but not the direct developing S. serrata. Patch size did play a role in determining limpet body size for both species. S. concinna body size was proposed to be effected directly by patch size whilst S. serrata body size was proposed to be affected indirectly by the effects of the S. concinna densities. The same patterns and trends were observed at five of the seven examined regions across the biogeographic range. The trends observed for S. concinna with respect to patch size conform to the source-sink hypothesis with large habitat patches acting as the source populations whilst the small habitat patches acted as the sink populations. Many previous studies have focused on the effects of habitat patch size at one point in time or over one season. I tested the influence of habitat patch size on the two species of limpets over a period of twelve months to determine whether the trends observed were consistent over time or whether populations varied with time. S. concinna showed a consistently significant difference between small and large patches; whilst S. serrata did not follow a consistent pattern. The mode of dispersal for the two limpets was used to explain the different trends shown by the two species. This examination allowed for the determining of source and sink populations for S. concinna through the examination of fluctuations in limpet body sizes and population densities at small and large habitat patches over twelve months. The direct developing S. serrata trends could not be explained using source-sink theory, as populations were independent from one another. S. serrata demonstrated body size differences at small and large patches which, may be explained by interspecific and intraspecific competition. Habitat isolation is known to play an important role in determining the structure of assemblages and the densities of populations. In this study the population density of the pelagic developing S. concinna showed a weak influence of degree of isolation whilst that of the direct developing S. serrata did not, which may be because of habitat patches along the South African coastline not having great enough degrees of isolation. The population size-structure was influenced directly influenced by isolation for S. concinna, whilst the different population size structure for S. serrata may be explained by assemblage co-dependence. The mode of dispersal showed effects on the relationship of population density and population size-structure with habitat size and isolation. This study indicates the importance of investigating patterns and processes across a range of spatial and temporal scales to gain a comprehensive understanding of factors effecting intertidal organisms.

Investigating the extent of local scale heterogeneity in assemblages is necessary to achieve a sound understanding of the processes giving rise to local assemblage patterns and the variation between them. Moreover, a clear understanding of local scale heterogeneity of assemblages is imperative in the development of effective regional conservation strategies. Previous studies examined the local scale heterogeneity in dung beetle assemblages between mixed woodland and sand forest habitats in Tembe Elephant Park, KwaZulu-Natal. Sand forest is an endangered habitat type in southern Africa which, when disturbed, opens up and changes towards mixed woodland. Reversion to the original sand forest structure after disturbance has never been recorded. Dung beetle assemblages were found to be homogenous within, but significantly heterogenous between, habitat types. It was therefore suggested that disturbance of sand forest (elephant foraging inside, and human occupation outside the Park) was likely to affect the assemblage structure of dung beetles in sand forest. Therefore, the aim of this study was to determine the effect of human- and elephant-induced disturbance on dung beetle assemblages in sand forest. Furthermore, disturbed sand forest dung beetle assemblages were predicted to be more similar to mixed woodland than to undisturbed sand forest assemblages. Disturbance by elephants causes sand forest vegetation structure to change to that of mixed woodland and this resulted in elephant-disturbed sand forest dung beetle assemblages becoming more similar to mixed woodland assemblages. Assemblages in human disturbed sand forest were unique and associated with human-related activities. The reliability and predictability of dung beetle indicator (species specific to a particular habitat type) and detector species (species indicative of the direction of habitat change) identified for Tembe in a previous study were tested. The results of this study largely supported the suite of bioindicator species first identified. Detector species were found to provide information complimentary to the indicator species and vegetation data available for sand forest. In addition, an identification key for the dung beetle species collected in Tembe Elephant Park to date was compiled. This key facilitates the use of dung beetle assemblages in indicator and monitoring systems in this reserve by providing a rapid and effective means of identifying the dung beetle species. The abundance-body size relationships of the dung beetle assemblages in mixed woodland, undisturbed and disturbed sand forests were also determined. Four hypotheses that account for the relationship between body size and abundance or its variants, were tested here, namely the energy equivalence rule, interspecific competition, differential extinction, and the biomass frequency distribution hypothesis. The disturbed sand forest assemblages were used to test whether disturbance alters the relationships between the macroecological variables (i.e. body size, abundance and biomass) and their interrelationships. This study provided some support for the biomass hypothesis. The major relationship between body size and abundance held despite human- and elephant-induced disturbance. Nonetheless, this study indicates that human- and elephant-induced disturbance alter sand forest dung beetle assemblages and may have significant implications for other taxa that occupy this endangered habitat type. Monitoring of the impacts of large herbivores on sand forest in reserves should thus be continued, and dung beetles provide one effective means by which this can be achieved. / Dissertation (MSc (Entomology))--University of Pretoria, 2001. / Zoology and Entomology / unrestricted

Thesis (M.S.)--Baylor University, 2009. / Includes bibliographical references (p. 53-55).

Made available in DSpace on 2015-06-17T19:34:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-09-26. Added 1 bitstream(s) on 2015-06-18T12:48:54Z : No. of bitstreams: 1 000830927.pdf: 1829000 bytes, checksum: 734f974335dd5f1dad129f0fe1150e4b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Atualmente, a instalação de pequenas centrais hidrelétricas (PCHs) tem sido a alternativa mais visada quando a questão é suprir a demanda energética considerando-se os menores impactos ambientais possíveis. Contudo, são escassos os trabalhos que avaliam as alterações causadas por esses empreendimentos. Este estudo procurou avaliar o impacto da construção de uma PCH sobre a fauna de macroinvertebrados aquáticos associados aos ambientes de pedrais. Para isso, amostras de macroinvertebrados foram coletadas em dois pedrais localizados no rio Sapucaí-Mirim (SP); o primeiro deles considerado como um pedral funcional, ou seja, que mantém as características naturais do rio, e o segundo, um pedral alagado em decorrência da instalação de uma PCH. As amostragens foram realizadas em dois períodos do ano e os dados avaliados através de análises multivariadas. Concluímos que a implantação da PCH acarretou alterações na composição e estrutura da comunidade de macroinvertebrados, com redução nos valores de riqueza, abundância e diversidade desses animais. Além disso, destacamos o fato de a construção de pequenas barragens interferirem no processo de transporte e sobrevivência dos organismos, alterando os sistemas a jusante. Assim, sugerimos que a manutenção de pedrais ao longo do rio é fundamental para conservação da biodiversidade aquática regional / Small hydroelectric power plants are the most used alternative to generate and provide electricity with less environmental impact. Nevertheless, there are few studies which evaluate the environmental alterations caused by these projects. The present study aimed to evaluate the impacts of a small hydroelectric power plant on the aquatic macroinvertebrate fauna associated to riffles. The macroinvertebrates were sampled in two riffles in the Sapucaí-Mirim River (São Paulo State, Brazil); the first one was considered as functional, maintaining the natural characteristics of the river; the second riffle was considered as non-functional due to its permanent flooding after the building of the small hydroelectric power plant. The samplings were carried out in two seasonal periods and the data were analyzed through multivariate analysis. It was concluded that the implementation of the small hydroelectric power plant caused compositional and structural alterations of the macroinvertebrate fauna, with reduction of richness, abundance and diversity of these organisms. In addition, it was highlighted the interference of the small hydroelectric power plants in the downstream transportation and survival of organisms, changing downstream systems. It is suggested that maintaining riffles along the river allow the conservation of regional aquatic biodiversity

Orientador: Marcos Gomes Nogueira / Banca: Vírgínia Sanches Uieda / Banca: paulo Augusto Zaitune Pamplin / Resumo: Atualmente, a instalação de pequenas centrais hidrelétricas (PCHs) tem sido a alternativa mais visada quando a questão é suprir a demanda energética considerando-se os menores impactos ambientais possíveis. Contudo, são escassos os trabalhos que avaliam as alterações causadas por esses empreendimentos. Este estudo procurou avaliar o impacto da construção de uma PCH sobre a fauna de macroinvertebrados aquáticos associados aos ambientes de pedrais. Para isso, amostras de macroinvertebrados foram coletadas em dois pedrais localizados no rio Sapucaí-Mirim (SP); o primeiro deles considerado como um pedral funcional, ou seja, que mantém as características naturais do rio, e o segundo, um pedral alagado em decorrência da instalação de uma PCH. As amostragens foram realizadas em dois períodos do ano e os dados avaliados através de análises multivariadas. Concluímos que a implantação da PCH acarretou alterações na composição e estrutura da comunidade de macroinvertebrados, com redução nos valores de riqueza, abundância e diversidade desses animais. Além disso, destacamos o fato de a construção de pequenas barragens interferirem no processo de transporte e sobrevivência dos organismos, alterando os sistemas a jusante. Assim, sugerimos que a manutenção de pedrais ao longo do rio é fundamental para conservação da biodiversidade aquática regional / Abstract: Small hydroelectric power plants are the most used alternative to generate and provide electricity with less environmental impact. Nevertheless, there are few studies which evaluate the environmental alterations caused by these projects. The present study aimed to evaluate the impacts of a small hydroelectric power plant on the aquatic macroinvertebrate fauna associated to riffles. The macroinvertebrates were sampled in two riffles in the Sapucaí-Mirim River (São Paulo State, Brazil); the first one was considered as functional, maintaining the natural characteristics of the river; the second riffle was considered as non-functional due to its permanent flooding after the building of the small hydroelectric power plant. The samplings were carried out in two seasonal periods and the data were analyzed through multivariate analysis. It was concluded that the implementation of the small hydroelectric power plant caused compositional and structural alterations of the macroinvertebrate fauna, with reduction of richness, abundance and diversity of these organisms. In addition, it was highlighted the interference of the small hydroelectric power plants in the downstream transportation and survival of organisms, changing downstream systems. It is suggested that maintaining riffles along the river allow the conservation of regional aquatic biodiversity / Mestre

The study of biological diversity has seen a tremendous growth over the past few decades. Among the commonly used indices capturing both the richness and evenness of a community, the Berger-Parker index, which relates to the maximum proportion of all species, is particularly effective. However, when the number of individuals and species grows without bound this index changes, and it is important to develop statistical tools to measure this change. In this thesis, we introduce two estimators for this maximum: the multinomial maximum and the length of the longest increasing subsequence. In both cases, the limiting distribution of the estimators, as the number of individuals and species simultaneously grows without bound, is obtained. Then, constructing the 95% confidence intervals for the maximum proportion helps improve the comparison of the Berger-Parker index among communities. Finally, we compare the two approaches by examining their associated bias corrected estimators and apply our results to environmental data.