Molecular ecology of hybridization

Hybridization is an important feature of the evolution of many plant and an imal groups. On one hand, it can be viewed as a natural experiment that pro vides a window on evolutionary processes. On the other hand, it is a signif icant evolutionary process in its own right that can lead to the origin or merger of species. This chapter reviews the contributions of molecular appr oaches to our understanding of hybrid zone structure and dynamics, phylogeo graphy, reproductive isolation, introgression, and hybrid speciation. After concepts and terminology are clarified, the potential utility of different kinds of molecular markers for investigating hybridization is reviewed. Th is is followed by an examination of several models that predict the structu re and dynamics of hybrid zones and an exploration of empirical and theoret ical studies that test the validity of these models. Finally, I will review how molecular markers have informed our understanding of several consequen ces of hybridization, such as introgression, hybrid speciation, species ext inction, and phylogenetic incongruence.