A general framework to model the effects of fragmentation process on community diversity
Seminario I, presentado en el postgrado de Ecología del Instituto Venezolano de Investigaciones Científicas (IVIC) en Julio de 2003.
Resumen:
In the present, the acceleration of habitat destruction through human activities is dramatically changing the environment and threatening biodiversity worldwide. The main motivation to this work is to find a way to predict, how the process of habitat fragmentation alters the diversity of natural communities. First, I formulate an appropriate context, that will be useful to develop a theoretical framework for this problem. I search for a coherent concept of community, and a spatial framework to place this community (the habitat). Then, I use an abstraction of the complex process of fragmentation to define three phases dominated by different fragmentation effects. This is the general framework, in which I present the models reviewed. The first group of models are related to the question of how many species remains after habitat is loss or fragments are formed in one time step. This models predict random and deterministic species extinction during and after the process of fragmentation. The second group of models considered, intend to predict the effects of changing landscape structure after fragmentation. These landscape models document positive and negative effects of landscape composition and physiognomy. A third group of models are concerned with the persistence of species and communities in a fragmented habitat. They explore local and regional community dynamics in relation to patch size and patch isolation. The models already available make important predictions about the fate of communities in fragmented habitats. Communities diversity can diminish at every stage of the fragmentation process by different mechanism, but species don’t dissappear at random. In the worst scenario, communities in fragmented habitats might be dominated by few generalist invaders and poor competitors.
