Molecular, genetic and modelling techniques are central to ecology, providing valuable new tools for addressing complex ecological questions. Genes in the Environment presents a review of the recent research in this exciting and rapidly developing field, illustrating how such techniques have provided considerable new insights into our understanding of the dynamics of populations and communities. A diverse range of topics are covered, including community dynamics in soils and water, gene flow and spatial dynamics, and the evolution of pathogenic and symbiotic relationships. Organisms studied range from bacteria, viruses and fungi to insects, plants and fish. New light is thrown on such questions as: what is the relationship between population dynamics and the spatial patterns of genetic variation observed in fragmented populations?; how is genetic variation maintained?; what are the relative roles of gene flow and selection in the maintenance of clines? This volume will appeal to both advanced students and researchers interested in developments at the interface of molecular biology and ecology.