Additional Information on Chromosomal Structural Changes and Differentiation in Gossypium

may have only accompanied the differentiation process. However, some structural changes (a) may link or shelter a combination of genes having selective advantage in some ecological habitat; or (b) may link loci that are higjhly coadapted biochemically in their new relationship to one another (Snow, I960; Snow and Dunford, 1961). In both cases natural selection could fix the structural change in the population, but fixation in the former case would generally be confined to a population in a particular habitat; whereas in the second case, the structural change may have such a selective advantage that it would eventually replace the original karyotype of the species.