Experimental evolution of ecological niches in heterogeneous environments

Abstract

Organisms live in heterogeneous environments but fail to demonstrate optimal adaptation toil the totality of the ecological conditions they experience. This imperfection would result from trade-offs between ecologically relevant traits, which implies that trade-offs are the ultimate cause of major features of life such as biodiversity. Here, I selected bacterial populations in defined laboratory environments to test for the importance of differences in productivity and quality among alternative resources (Chapter 1), as well as the spatial pattern of resources (Chapter 2), in shaping the evolution of ecological niches and genetic diversity. The experiment presented in Chapter 1 provides support for a general model for the evolution of diversity. In Chapter 2 however, I suggest that mutational processes can impinge on the expression of trade-offs, which is not recognized in our current view of the problem of diversity. These findings provide plausible explanations for situations where expected trade-offs are not found.