In 1964, a symposium on “The Genetics of Colonizing Species” was held at Asilomar, California, which brought together “geneticists, ecologists, taxonomists, and scientists working in some of the more applied aspects of ecology – such as wildlife conservation, weed control, and biological control of insect pests” (Baker and Stebbins, 1965:vii). It was felt that the biology of colonizing species would be more readily understood using a multidisciplinary approach, and, in particular, the conference recognized the need for interaction between population genetics and ecology. Even so, after what was evidently a most stimulating meeting, Mayr (1965) in his summary paper wrote, “The one firm conclusion I can draw is that it is quite impossible to summarize the conference.” Since then, there has been progress, but it has been rather sporadic, often arising from investigations having other primary objectives. This book was written in the belief that this situation is about to change. For example, there is renewed interest in attempts at genetic analyses of ecologically significant complex traits, such as life-history characteristics, environmental stresses, and the use of feeding and breeding sites in relation to habitats occupied.

Until recently, genetics, ecology, and the study of behavior have been regarded as separate entities. This view is not realistic in the development of a coherent evolutionary biology of an organism, and we should look forward to a unification of all three disciplines. Nowhere is this more evident than in the study of colonists in their habitats. By using colonizing species as a case study, an object of this book is to demonstrate the importance of such a unified approach.