The following dynamics with respect to genetic variation are indicated. With increasing complexity of stress conditions, heterozygosities tend to be larger in tolerant subsets as compared to the sensitive ones.
Genetic multiplicity is reduced in juvenile populations under field stress.
Genetic diversity increases in tolerant subsets as a consequence of changes in frequency distributions, i.e. a trend towards larger eveness. Viability selection with substantially changing allele frequencies is obvious only under relatively homogeneous environmental conditions. Complex and long lasting environmental stress seems to result in complex genetic response at the multi-locus level. Direction of genetic selection clearly varies among ontogenetic stages. Genetically diverse individuals and subsets obviously show a viability advantage under complex environmental stress.