Speciation is one of the great themes of evolutionary biology. It is the process through which new species are born and diversity generated. In this volume, thirty authors at the forefront of research into speciation present the newest findings from their studies and bring readers up to date on species concepts, modes of speciation, the nature of reproductive barriers, the forces that drive divergence of populations, the genetic control of reproductive isolation, and the role played by hybrid zones and hybridization in speciation.