UNT Theses and Dissertations - 3 Matching Results
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- Effects of Macrophyte Functional Diversity on Taxonomic and Functional Diversity and Stability of Tropical Floodplain Fish Assemblages
- Multiple dimensions of biodiversity within and across producer and consumer guilds in the food web affect an ecosystem’s functionality and stability. Tropical and subtropical aquatic ecosystems, which are extremely diverse, have received much less attention than terrestrial ecosystems in regards to the effects of biodiversity on ecosystem functioning. We conducted a field experiment that tested for effects of macrophyte functional diversity on diversity and stability of associated fish assemblages in floodplain lakes of the Upper Paraná River floodplain, Brazil. Three levels of macrophyte functional diversity were maintained through time in five floodplain lakes and response variables included various components of fish taxonomic and functional diversity and stability. Components of functional diversity of fish assemblages were quantified using a suite of ecomorphological traits that relate to foraging and habitat use. Response variables primarily distinguished macrophyte treatments from the control. Macrophyte treatments had, on average, double the number of species and total abundance than the control treatment, but only limited effects on stability. The high diversity treatment was essentially nested within the low diversity for assemblage structure and had similar or even slightly lower levels of species richness and abundance in most cases. Gymnotiformes and young-of-year were diverse and relatively abundant in macrophyte treatments contributing to the large differences in diversity between macrophyte and control treatments. Higher fish diversity in structured habitats compared to more homogenous habitats is likely associated with increased ecomorphological diversity to exploit heterogeneous microhabitats and resources provided by the macrophytes.
- Stock Returns and the Brazilian Default an Analysis of the Efficient Market and Contagion Effect Hypotheses
- This thesis attempts to analyze the market response of stock prices of major U.S. banks to the February, 1987 Brazilian loan default announcement. The study's general hypothesis is that the market revalued stock prices according to each bank's amount of Brazilian loan exposure. The first chapter examines the significance of the default announcement. A survey of related literature is presented in the second chapter. Chapter III specifies the methodological techniques involved in analysis of the data. Chapter IV reports the findings of the study. Conclusions about the results are drawn in Chapter V. The results indicate the market is efficient. They also suggest that individual exposure was the major determinant of bank stock price decline.
- The Development of the Sugar, Rubber, and Cotton Industries in Brazil
- In this study of the development of the sugar, rubber, and cotton industries in Brazil, the writer proposes to show the development of these industries from the beginning of the industries to about 1947.