[Investigations on the interaction of selection and selfing on genetical equilibrium : Especially in tetraploid...

In the second part of this paper the influence of genotypically determined outcrossing rates on the genetic variability of diploid populations has been investigated. In the proposed model it has been assumed that besides self-pollination the plants share in a common pollen pool. Populations with and without selection have been taken into account. The investigations led to the following results: 1. Selfing of a genotype tends to have the same effect as selection in favour of this genotype. 2. Outcrossing rates of T 1>T 2=T 3 and T 1=T 2T 2 stable non-trivial equilibria with values of p=0.5 are possible. For this case formulas for calculating the frequencies of genotypes have been specified. 3. Outcrossing rates of T 1≠T 2≠T 3 lead in case of relations of T 1>T 2>T 3 to a fixation in a(2). Relations of T 1>T 3>T 2 respectively T 3>T 1>T 2 allow, beside a trivial stationary state, also the maintenance of a stable polymorphism. Calculations of the frequencies of genotypes are possible when the formulas specified are used. In case of the heterozygotes having the lowest selling rate, only trivial stationary states are possible, and are depending on the initial frequency. 4. Selection in favour of a genotype intensifies the effect of selling this genotype. In case of antagonism of the two factors, relatively small differences between fitness values may compensate for the effect of selfing. On the other hand, large differences between the outcrossing rates of the genotypes are necessary in order to compensate for the influence of selection.