Biology Department, St. Lawrence University, Canton, NY, USA.
Horizontal gene and genome transfer forces us to recognize that life evolves by fusion as well as bifurcation of lineages, and necessitates the expansion of traditional views of evolution. This chapter reviews the role that horizontal gene transfer (HGT) may play in integrating selection at the gene, species, and community levels. Additionally, we provide an overview of the structure and content of this book, which reflects current thought in the dynamic field of HGT research.