Genetics of speciation in rice

Abstract

One of the central issues of evolutionary biology is the origin of the species, although the definition of species is an endlessly debated issue (Coyne and Orr 2004). According to the biological species concept (BSC), a species is a group of an actually or potentially interbreeding natural population, which is reproductively isolated from other such groups (Mayr 1942). No concept of speciation could be complete without a genetic interpretation of the rise of isolating mechanisms. Fitness reduction can range from maladaptation to inviability or sterility. The loci that underlie such reduction in fitness might be considered ‘speciation genes’, which are important in driving the nascent species to become independent genetic entities (Wu and Ting 2004). Therefore, we can analyze the genetic basis of speciation as a more tractable problem by focusing on the genetic basis for reproductive isolation. Recent work on reproductive isolation in Drosophila has advanced our understanding of many fundamental questions about speciation (see review in Coyne and Orr 2004). The BSC can be favorably adopted regarding domesticated plants, and the concept of gene pools based on the degree of their sexual affinities is useful for their classification (Harlan 1975). Any good species are by no means completely isolated. Wild and cultivated complexes in crops are taxonomically distinct but phylogenetically conspecific. Their genetic differentiation is maintained through disruptive selection associated with habitat adaptation, indicating that domestication proceeds at the intra-specific level under human influence.