BIOCOMPLEXITY-Evolution and Ecology of Perturbed Interactions: Modeling Disequilibria in Time and Space

Perturbation of biological communities, exemplified by habitat loss and the invasion of novel taxa is well documented. Economic development, new technologies, and population pressure have escalated the scale, frequency, and severity of such perturbations. As a result, evolutionary and ecological dynamics may be driven so far from their equilibria that the linear approximations used for understanding and predicting consequences of subtle perturbations are inappropriate and probably misleading. To elucidate the consequences of massive perturbations in biological communities, a spatially explicit model whose dynamics are complicated by ecological, genetic, and historical factors, is proposed. Studies on (i) corn smut and corn, (ii) rhizobia associated with common bean, (iii) corn borer and genetically modified Bt and non-Bt corn, and (iv) prairie plants and their pollinators provide the empirical basis that are framed by the general model of interactions between hosts and their associates. A hierarchy of models at different spatial scales will determine the evolutionary and ecological role of different factors at the different spatial scales. In addition, statistical tools are used to develop and analyze data of genetic diversity under non-equilibrium conditions using both temporal and spatial information.

Understanding the complex interactions between the members of communities undergoing such massive perturbations and their evolutionary and ecological consequences requires the integration of empirical work and mathematical models across temporal and spatial scales. The empirical studies represent examples of large perturbations that occurred either in the past (as in (i) and (ii)) or in the present (as in (iii) and (iv)). The historical studies allow testing the predictability of the theoretical models to assess the accuracy of the predictions for the consequences of massive perturbations that occur presently. The perturbations consist (1) of the introduction of novel organisms or (2) of habitat destruction, both at a large spatial scale: Corn and beans were moved from South and Central America to North America in the past carrying with them microorganism that, after introduction, competed with already present microorganisms. Bt corn is currently being introduced in North America as a control mechanism for the European corn borer, a devastating pest of corn; Bt corn is introduced at a large spatial scale that introduces large selection pressure on the evolution of resistance to Bt corn, which will make this control mechanism ineffective. Habitat destruction is an ongoing process affecting nearly every natural community in North America and in other parts of the world leading to loss in biodiversity. The goal is to predict the evolutionary and ecological consequences of large range expansions and contractions of plants on their associated biological communities in order to better manage natural and agricultural systems.