Thesis (Ph. D)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Cliff Montagne. Includes bibliographical references.

A influência da estrutura ambiental sobre os padrões de diversidade da ictiofauna de ecótonos são analisados para o reservatório do Broa, bacia do rio Tietê (22º10\'S; 47º54\'W). Paralelamente, são avaliadas as alterações na composição dessa comunidade entre 1985 e 2000. Constituída por 24 espécies (sete ordens e 12 famílias de peixes) e com um alto nível de diversidade (1,99 bits./ind.), a ictiofauna estudada não apresentou variação espacial ou temporal na abundância de suas espécies. Os padrões de baixa captura e freqüência das quatro espécies introduzidas, parecem não evidenciar risco potencial de impacto negativo aos estoques hospedeiros. Determinadas principalmente pelo fluxo d\'água e estado trófico, as variáveis ambientais evidenciaram as alterações estruturais a que ecótonos estudados vêm sendo submetidos. Apesar da ausência de variação significativa entre a estrutura da ictiofauna de zonas de transição e bancos de macrófitas, perante a sazonalidade, essas taxocenoses apresentaram distintos padrões de composição, estabilidade e variação estrutural. Bancos de macrófitas tornam a área alagada mais heterogênea, constituindo comunidades com maior riqueza e diversidade de espécies, sendo drasticamente afetadas pela sazonalidade. Entre as espécies constantes, 90% estiveram ordenadas junto aos bancos de macrófitas, onde variações na disponibilidade de recursos críticos (p.e. alimentação e abrigo) segregam nas sazonalmente, enquanto fluxo d\'água e estado trófico são os gradientes determinantes dos habitats de abundância predominante das espécies. / The influence of environmental aspects on diversity patterns for the ichthyofauna of ecotones were analyzed for the Broa reservoir, Tiete river basin (22º10\'S; 47º54\'W). Alterations in the ichthyofauna composition have also been analyzed considering the period from 1985 and 2000. This fauna constituted by 24 species (seven orders and 12 families) and a high diversity (1,99 bits/ind.), showed no spacial or temporal variations in species abundance. The pattern of low capture and frequency of four species introduced in inchangeable, not pointing out to the risk of a potential negative impact over the native species. Determined mainly by the inflow and trophic condition, the environmental variables show clearly the structural alterations that these ecotones studied have been undergoing. Although there was no significant seasonal variation between the ictiofauna structure of the transitional zones and macrophytes banks, these taxocenoses presented a distinct composition pattern, stability and structural variation. Macrophytes banks increase the environmental heterogeneity of wetland areas, resulting communities with high species diversity, being drastically affected by seasonality. Between the constant species 90% ordained along macrophytes banks, variations on the availability of critical resources (f.e. food and shelter) cause for the seasonal segregation of these species, inflow and trophic condition were the determinant gradients on the principal habitats occupied by the species.

A influência da estrutura ambiental sobre os padrões de diversidade da ictiofauna de ecótonos são analisados para o reservatório do Broa, bacia do rio Tietê (22º10\'S; 47º54\'W). Paralelamente, são avaliadas as alterações na composição dessa comunidade entre 1985 e 2000. Constituída por 24 espécies (sete ordens e 12 famílias de peixes) e com um alto nível de diversidade (1,99 bits./ind.), a ictiofauna estudada não apresentou variação espacial ou temporal na abundância de suas espécies. Os padrões de baixa captura e freqüência das quatro espécies introduzidas, parecem não evidenciar risco potencial de impacto negativo aos estoques hospedeiros. Determinadas principalmente pelo fluxo d\'água e estado trófico, as variáveis ambientais evidenciaram as alterações estruturais a que ecótonos estudados vêm sendo submetidos. Apesar da ausência de variação significativa entre a estrutura da ictiofauna de zonas de transição e bancos de macrófitas, perante a sazonalidade, essas taxocenoses apresentaram distintos padrões de composição, estabilidade e variação estrutural. Bancos de macrófitas tornam a área alagada mais heterogênea, constituindo comunidades com maior riqueza e diversidade de espécies, sendo drasticamente afetadas pela sazonalidade. Entre as espécies constantes, 90% estiveram ordenadas junto aos bancos de macrófitas, onde variações na disponibilidade de recursos críticos (p.e. alimentação e abrigo) segregam nas sazonalmente, enquanto fluxo d\'água e estado trófico são os gradientes determinantes dos habitats de abundância predominante das espécies. / The influence of environmental aspects on diversity patterns for the ichthyofauna of ecotones were analyzed for the Broa reservoir, Tiete river basin (22º10\'S; 47º54\'W). Alterations in the ichthyofauna composition have also been analyzed considering the period from 1985 and 2000. This fauna constituted by 24 species (seven orders and 12 families) and a high diversity (1,99 bits/ind.), showed no spacial or temporal variations in species abundance. The pattern of low capture and frequency of four species introduced in inchangeable, not pointing out to the risk of a potential negative impact over the native species. Determined mainly by the inflow and trophic condition, the environmental variables show clearly the structural alterations that these ecotones studied have been undergoing. Although there was no significant seasonal variation between the ictiofauna structure of the transitional zones and macrophytes banks, these taxocenoses presented a distinct composition pattern, stability and structural variation. Macrophytes banks increase the environmental heterogeneity of wetland areas, resulting communities with high species diversity, being drastically affected by seasonality. Between the constant species 90% ordained along macrophytes banks, variations on the availability of critical resources (f.e. food and shelter) cause for the seasonal segregation of these species, inflow and trophic condition were the determinant gradients on the principal habitats occupied by the species.

Ecotones are gradients of change between expanses of similar species composition. These regions often mark co-occurring range limits for several species, and thus are ideal for elucidating ecological and biogeographical phenomena. The forest to tundra transition (FTT) is one of the world's most prominent ecotones, but remains poorly studied especially with regard to vertebrate species occurrence. Vertebrate diversity, ecological structure and resource selection were characterized across the Yukon FTT using diversity metrics, ordination, hierarchical clustering, and resource modeling. The FTT represents an abrupt drop in vertebrate species richness within the more gradual, continental scale diversity gradient. Despite the patchiness and complexity in vegetative structure over this ecotone, the terrestrial vertebrate community is divisible into boreal, taiga, and tundra compartments. Most species conform to resource associations reported closer to the core of their range, generating remarkably consistent habitat and species associations despite a complex patchwork of contrasting habitat types.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 8, 2008) Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaves 88-105) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaves 88-105) Also available online.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 25, 2007) Vita. Includes bibliographical references.

Thesis (Ph. D.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 7, 2007) Includes bibliographical references.

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