Estudo dos efeitos da distribuição de recursos em um ecossistema sobre a biodiversidade

Abstract

Competition is one of the most important forms of interaction among individuals, as well as mutualism and predation, and occurs when there is a common need for a limited resource. Competition theory afirms that in equilibrium, the number of competing coexisting species can not exceed the number of limiting resources in an ecosystem, known as the Principle of Competitive Exclusion. However, there is a biodiversity riddle for aquatic ecosystems, where a limited amount of resources are found to support the coexistence of a wide variety of phytoplankton species, called the Paradox of the Plankton. Experimental results show a unimodal relationship between species diversity and the amount of resources. In this work, our main goal is to study the effects of the amount of resources available in an ecosystem on diversity using a computational model with spatial structure. We investigate how the distribution of resources in the ecosystem, as well as the quantity that is available to each one, affects ecosystem equilibrium. We note that the increase in spatial heterogeneity leads to the growth of the number of species until it reaches a peak for intermediate heterogeneity, and decreases for larger heterogeneities. Considering that the variation in the quantity available for each resource affects the number of species present in the equilibrium we vary this quantity in order to observe the effects caused on the diversity of the species. We observed that for habitats with low heterogeneity the diversity grows with the increase of the amount of resources, and for habitats with high heterogeneity the diversity decreases, whereas a unimodal relation is observed for values of intermediate heterogeneity.