Weak selection

Weak selection, therefore, is an evolutionary theory to explain the maintenance of multiple phenotypes in a stable population.

Consequently, weak selection provides a model for describing how evolution can occur in large steps in a population in which multiple alleles are maintained.

[1] Weak selection creates a situation in which the evolutionary dynamics governing the phenotype frequencies in a population are mainly driven by random fluctuations.

In smaller populations, a weakly selected mutation could proliferate due to stochastic processes such as genetic drift even more easily.

Furthermore, weak selection operates in codon-usage bias resulting in differential levels of gene expression by altering the rate of transcription in mutants with non-preferred codons.