On The Origin of Speciation

Charles Darwin proposed the theory of evolution that natural selection leads to the evolution of organisms in "On the Origin of Species”, but did not show the mechanism by which new species differentiate and fix. Speciation requires a system in which genes are not mixed by interspecific hybridization, and reproductive isolation, especially postmating reproductive isolation, is considered to be the most reliable as guarantee. Haldane proposed that heterogametic sex was absent, rare or sterile in interspecific hybrid F1. Dobzhansky and Muller predicted that postmating reproductive isolation occurs when mutations occurring at two or more interacting loci exhibit incompatibility in the hybrid. Genes that satisfy these observation and prediction are considered speciation genes. Here, I would like to review the findings on reproductive isolation and speciation to consider the candidate conditions for the speciation genes, and present the genes that fit these conditions.