Reproductive isolation is generally regarded as the essence of the speciation process. The evolution of reproductive isolation allows differentiation and permits local adaptations to become fixed in diverging populations. Studying closely related species is convenient for understanding the genetic basis of this process. With this in mind, Nadir et al. restricted their subject species to the Oryza sativa complex, which includes the two domestic rice cultivars and six wild relatives. Although closely related, these rice species are separated from each other by a range of reproductive barriers.
The comprehensive review, recently published in AoBP, evaluates current understanding of the forces that shaped the formation of reproductive barriers among and between the species of the O. sativa complex; including pre-zygotic barriers, such as differing floral morphology and offset flowering time, and post zygotic barriers, such as reduced F1 hybrid viability, vigour and sterility. The authors conclude by offering some future research perspectives and highlight the potential of the Oryza sativa complex as a model system for the future study of speciation.