Modelagem de ecossistemas com competição por recursos em relevos correlacionados

Abstract

There is no doubt about the importance of experimental and computational research in biology, specifically in Ecology, given the limited knowledge about the nature. With increased computational possibilities, studies by simulations have grown considerably, despite the limitations of computational time and the complexity of nature require specific analysis. However, all contributions are important to the knowledge progress in this direction. In this thesis, computational studies on competition for resources with spatial structure were carried out, in order to observe how some aspects of spatial ecosystem structure can influence the diversity of species. The body of research was divided into two parts. At first, the environment was fragmented before the network occupation with the species, and the resources were distributed evenly across subregions, ranging heterogeneity by the number of these subregions. The type of fragmentation was promoted through a fractal structure, correlating the non-inhabitable sites by Hurst exponent, using the fractional Brownian motion (fBm), besides being considered different fragmentation percentage. In the second part of the study, the environment was not fragmented and resources were also correlated using the fBm for generating a correlated relief. In both studies, the species-area relationship was analyzed, abundance and distribution of the relationship between diversity and heterogeneity of resources. In the first study, concerning to the species-area relationship, two schemes in power law are observed, and were investigated the values of the exponents for each case. A higher diversity and higher exponents for intermediate heterogeneities were observed. In general, for large and intermediate areas, species diversity decreased with increasing Hurst exponent, fixed the percentage of fragmentation. For small areas, there wasn’t considerable variation in diversity with increased Hurst exponent and the percentage of fragmentation. Fixed the value of the Hurst exponent and heterogeneity of resources, diversity increased with increasing fragmentation. This happened more highly for extreme heterogeneities (low and high) and lower values of the Hurst exponent, less pronounced for intermediate heterogeneities. Increasing the value of the Hurst exponent, the variation in the percentage of fragmentation caused no significant difference in diversity, especially for intermediate heterogeneities. Regarding the distribution of abundance, it was observed that both the Hurst exponent, the heterogeneity and the fragmentation percentage influenced the distribution, verifying a bimodal distribution for intermediate heterogeneities. In the second study, in which the correlated resources by the Hurst exponent, were observed, for different values for the Hurst exponent, a behavior of the species-area ratio with two schemes power law. For higher values of the Hurst exponent, the diversity of species is somewhat lower. For small areas, diversity is slightly larger for small values of this exponent and for large areas the maximum diversity is given to an intermediate value of the Hurst exponent. Still, there was no major differences in the species-area relationship with the variation of the Hurst exponent. Analyzing the distribution of abundance, there was a unimodal relation to the different Hurst values, noting highest peaks for intermediate values of this exponent, although no significant differences.