Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value.
These pathways consist of disruptive selection being based on intraspecific competition, which often leads to reproductive isolation, and finally sympatric speciation.
While it is true that disruptive selection can lead to speciation, this is not as quick or straightforward of a process as other types of speciation or evolutionary change.
It is actually fairly common to see sympatric speciation when disruptive selection is supporting two morphs, specifically when the phenotypic trait effects fitness rather than mate choice.
Disruptive selection is seen in high density populations rather than in low density populations because intraspecific competition is more common when accompanied by a higher density population.