The Role of Hybridization and Introgression in the Diversification of Animals

TLDR

Hybridization and introgression are recognized drivers of plant diversity, yet their role in animal diversification remains uncertain; animal hybrids are rare, possibly due to bias and detection limits, yet they have produced unique polyploid and unisexual complexes that can promote diversification. This review aims to reassess the importance of introgressive hybridization in animal evolution and diversification, questioning the prevailing negative view of these processes. By synthesizing recent literature and leveraging advances in detection and changing attitudes toward hybrids, the authors evaluate evidence for hybrid origins and their evolutionary impact in animals.

Abstract

Although hybridization and introgression have been considered important in generation of plant diversity, their role in evolutionary diversification of animals remains unclear. In this review, we reconsider the significance of introgressive hybridization in evolution and diversification of animals to determine if the generally negative assessment of these processes is warranted. Unlike the situation for plants, hybrid animal taxa appear to be relatively rare. This could, however, be due to negative attitudes toward hybridization and difficulty in detecting such forms. Hybridization has been responsible for instantaneous creation of several unique complexes of polyploid and unisexual animals. Allopolyploidy has allowed for diversification, whereas unisexual taxa have acted as conduits of gene exchange among related sexual species. Many instances of diploid, bisexual taxa of hybrid origin have been put forward, but few have been carefully tested. Changing attitudes toward hybrids and technological advances should allow for careful consideration of hypothesized hybrid taxa and will undoubtedly increase the number of known animal hybrid taxa.