SYMPATRIC SPECIATION - A SIMULATION-MODEL OF IMPERFECT ASSORTATIVE MATING

The computer model of sympatric speciation (Fialkowski, 1988, J. theor. Biol. 130, 379) has been expanded and partial assortative mating incorporated. The model is intended as a working hypothesis and offers proposals for further research on sympatric speciation. As a working hypothesis it states that sympatric speciation should be looked for in populations where heterozygotes' fitness is below the average fitness of homozygotes and that assortative mating can be incubated in particular cases of stable conditions determined by Maynard Smith & Hoekstra (1980, Genet. Res. 35, 45) when polymorphs co-exist without heterozygotic overdominance. The hypothesis states that two different mechanisms of sympatric speciation exist: the first mechanism is operational in rather stable environments and (taking into account reversibility of the speciation process) may last as long as a million generations; in this mechanism a population in equilibrium is "eroded from inside". The cases when the emergence of nascent species is not accompanied by any change in environment should be researched to establish its biological existence. The second mechanism of emergence of the two populations is extremely fast (usually less than 200 generations) and is the result of notable changes in the environment. The hypothesis states that increased homozygosity in populations must exist and be observed at least temporarily as a distinct deviation from the Hardy-Weinberg recombination principle. © 1992 Academic Press Limited All rights reserved.