Summary
Selection favouring both extremes over the average, which may lead to divergence.
In depth
Both extremes are favoured, and the mean is selected against, so the distribution becomes bimodal. It may start sympatric speciation.
It maintains polymorphism and can split a population: in the African black-bellied seedcracker (Pyrenestes ostrinus), birds have either large or small beaks, matched to hard and soft seeds, and medium-billed birds feed poorly. Similar patterns occur in stickleback fish (limnetic and benthic forms) and in Darwin's finches.
If combined with assortative mating, disruptive selection can lead to speciation. In the lab, experiments with fruit flies selected for extreme bristle numbers produced two groups with reduced interbreeding.
Remember: the distribution gets wider and may become two-peaked, with the mean being the least fit.
Frequently asked questions
What is Disruptive Selection?
Selection favouring both extremes over the average, which may lead to divergence.
Which area of biology covers Disruptive Selection, and how advanced is it?
Disruptive Selection is one of the 53 topics in Evolution. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Stabilising Selection, Speciation, Sympatric Speciation.
Can you give an example of Disruptive Selection?
African seedcracker finches have two bill sizes suited for hard or soft seeds, with few intermediates.
What should I learn before Disruptive Selection?
Work through the Beginner topics in Evolution first, such as Evolution, Natural Selection, Charles Darwin, then return to Disruptive Selection. Intermediate topics assume the Beginner vocabulary.
What topics are related to Disruptive Selection?
The closest topics to Disruptive Selection are Stabilising Selection, Speciation, Sympatric Speciation, Natural Selection. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Disruptive Selection?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Disruptive Selection. To practise the whole of Evolution, use the Evolution quiz.
How is Disruptive Selection different from Stabilising Selection?
Disruptive Selection: Selection favouring both extremes over the average, which may lead to divergence. Stabilising Selection: Selection favouring intermediate phenotypes, as seen in human birth weight. Read both side by side and note what each one explains.
How should I study Disruptive Selection step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Stabilising Selection and explain the difference aloud. Finally, take the Evolution quiz and come back to this page for any question you miss.