Darwin's model of speciation in his unpublished notebooks and texts

It is by now well-known that gene-flow is not the only cohesion factor in species-populations. Yet speciation theory focuses mainly the evolution of genetic barriers. Darwin's model of speciation is by no means as chaotic a claimed in the literature. To the contrary, Darwin followed in his complex speciation model exactly the technique of breeders of plants and animals. The goal of the natural breeding process is to evolve those cohesion factors that Darwin regarded as the most important: the sharing of an independent, well-developed niche, and gene-flow within a rather uniform gene-pool. The roots of most presently recognized speciation models can be found in Darwin's texts, including (i) allopatric, (ii) founder principle, (iii) clinal, (iv) stasipatric and (v) sympatric speciation.