Definition of Disruptive Selection
Disruptive selection is an evolutionary force that isolates the population. This selection will compel the organisms having intermediate traits to reproduce less and those organisms will tend to reproduce more which have extreme traits. In this way, the alleles of extreme traits would increase in frequency. The population becomes completely divided when there is enough disruptive selection.
Under such circumstances, separate species are formed from such diverse populations. The variance of a trait in a population becomes the basis of disruptive selection. There would be no variance if the gene has only one allele. On the other hand, the genes which have a number of alleles create a large variety of functions.