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Understanding Evolution

Understanding Evolution

Your one-stop source for information on evolution

Understanding Evolution

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Home → Triggering adaptive radiation
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Triggering adaptive radiation

An adaptive radiation generally means an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations. Different factors may trigger adaptive radiations, but each is a response to an opportunity.

A beetle with striped wings sits on top of a yellow flower
Beetle radiations may have been triggered by adaptations for feeding on flowering plants. Photo © Windsor Aguirre

The evolution of a key adaptation

A key adaptation usually means an adaptation that allows the organism to evolve to exploit a new niche or resource. A key adaptation may open up many new niches to an organism and provide the opportunity for an adaptive radiation. For example, beetle radiations may have been triggered by adaptations for feeding on flowering plants.

Release from competition/vacated niches

Lineages that invade islands may give rise to adaptive radiations because the invaders are free from competition with other species. On the mainland, other species may fill all the possible ecological niches, making it impossible for a lineage to split into new forms and diversify. On an island, however, these niches may be empty. Extinctions can also empty ecological niches and make an adaptive radiation possible. For example, open niches vacated by dinosaur extinctions may have allowed mammals to radiate into these positions in the terrestrial food web.

The extinction of the dinosaurs at the end of the Cretaceous may have allowed mammal radiation.

Specialization

Specialization may subdivide a single niche into many new niches. For example, cichlid fishes have diversified in East African lakes into more than 600 species. This diversification may have been possible because different fish lineages evolved to take advantage of different foods (including insects, algae, mollusks, small fish, large fish, other fishes’ scales, and even other fishes’ eyes!).

This image shows different Cichlid fishes of Lake Malawi
Cichlid photos courtesy of Michael K. Oliver, Ph.D.

 

  • Evo Examples

Learn more about adaptive radiations in context:

  • Using trees to understand plants: The work of Chelsea Specht, a research profile.
  • Happy 200th, Darwin!, a news brief with discussion questions.

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