Natural hybridization and speciation

Abstract

Natural hybridization plays a pivotal role in the formation of new species during the evolution of organisms. There are two principal types of hybrid speciation: polyploidization and homoploid hybrid speciation. The former has been regarded as an important force driving plant speciation, whereas the latter has proved to be a main mode of speciation based on an increasing number of cases, which have reported successful crosses between the species at the same ploidy level. However, only a few cases of homoploid hybrid speciation have been documented when strict criteria are applied. Therefore, molecular evidence involving more genomic loci and morphological investigations from different kinds of hybrid zones, as well as assessments of existing speciation models and new computer stimulations, are required for further understanding the genetic basis of the initial and entire process of speciation. Through the historical reconstruction of gene flow between diverging lineages, additional organismal models for hybrid speciation need to be developed to reveal the effects of natural selection on the formation of reproductive isolation, and to discern the ecologically adaptive changes and the formation rules of novel diversity in the process of hybrid speciation. Here I briefly review the history of studies examining natural hybridization and speciation to introduce concept changes, research methods, and the latest advances of natural hybridization and speciation, to identify the unsolved core and basic scientific questions and to provide feasible suggestions for future studies and the protection of biodiversity involved in natural hybridization.