Hybridization in Animal Evolution

In the past two decades, it has become clear that hybridization is so common in animal species as to be an almost universal feature of their evolutionary histories. Remnants of both ancient and contemporary hybridization events are present in the genomes of modern species, but their consequences are still not completely understood. In this review, we synthesize what is known about the evolutionary and genetic drivers of ancestry variation across the genome, highlighting mechanisms that play an important role in many species groups including the impacts of the local recombination rate and the role of selection in the earliest generations following hybridization. We discuss advances in our understanding of the long-term evolutionary consequences of hybridization, including the role of introgression in adaptation, and the factors that shape these consequences. We conclude with a discussion of the impacts of hybridization on conservation efforts and outline outstanding challenges in the field.