[Simulation of populations with randomly fluctuating fitness values].

The behaviour of populations due to fluctuating fitness values has been investigated using a computer. Six model systems were considered. The results have been illustrated by figures showing the composition of the populations as a function of the number of generations. The curves obtained for the genotype frequencies of the zygotes and adults (Z i and f i) from repeated runs have been analysed statistically by characteristic parameters as means, relative variances RV zi and RV fi and fluctuation frequencies. The study gave the following results: 1. The value of the parameters is determined by the selection coefficient s, the relative variance of the fitness values RV wi, the position of the deterministic equilibrium and the fertilization system. 2. In the systems without selfing the extent of the fluctuations, measured by RV zi and RV fi, primarily is caused by RV wi; the fluctuation frequency, as a measure for the length of time of the deviation from the mean, on the contrary is determined by s. 3. Equal rates of selfing (S i) of the three genotypes and lesser rates of selfing of the heterozygotes (S 2 < S 1 = S 3) extend, whereas greater rates of selfing of the heterozygotes (S 2 > S 1 = S 3) reduce, the fluctuations. 4. In all systems the mean of the frequency of the heterozygotes was smaller than the value of the deterministic equilibrium. The size of the difference, called heterozygote decrease A z2 resp. A f2, showing dependencies similar to RV zi and RV fi. 5. The relative variances of the heterozygote frequencies ordinarily were lower than those of the homozygote frequencies. This means that the heterozygote frequencies are less influenced by fluctuations of the fitness values.