Genetic variation in a heterogeneous environment. V. Spatial heterogeneity in finite populations.

The spatial model of Levene (1953) was examined in a finite population and compared to a temporal model. The spatial model was much more effective in retaining genetic variation in a finite population. Furthermore, the haploid spatial model was more effective in retaining genetic variation than the analogous diploid absolute dominance model. This is the opposite from that found for the temporal model, where the diploid model was more effective than the haploid. Here is an example where diploidy (sexual reproduction) may be disadvantageous. A model that permitted both spatial and temporal variation to act in concert gave retention of genetic variation in situations where either spatial or temporal variation, separately, did not. The relationship between the amount of heterozygosity and the retardation factor was discussed. An example of how spatial or temporal variation affects the proportion of populations fixed after a certain number of generations was given. It seems that these models have biological analogues, several examples of which are mentioned.