Lecture 19 Adaptive Radiation & Convergent Evolution

What is adaptive radiation?

The diversification of members of a single phylogenetic lineage (clade) into a variety of different forms under the action of natural selection

What are the four common causes of adaptive radiation?

Environmental change
Mass Extinctions
Invasion of Island Archipelagoes
Key Innovations

What are some examples of adaptive radiation?

"Mammals
Hawaiian Honeycreepers
Bromeliads
Anolis Lizards
Horned Lizards (Phrynosoma)
Darwin's (Galapagos) Finches
African Rift Valley Cichlid Fishes"

What are key innovations?

A derived characteristic (morphology; behavior; physiology) that allows a new way of life that may lead to adaptive radiation

What is key innovations also known as?

"General adaptations"

What are some examples of key innovations?

Flight
Amniotic (cleidoic) egg
Ability to digest cellulose
Endothermy

Why are key innovations hard to test in a rigorous fashion?

Many putative key innovations are unique evolutionary events
Evidence is like what we have when comparing only two species
Could easily just be a coincidence

What is convergent evolution?

Occurs when unrelated species independently evolve similar traits or features often because they adapt to similar environments or ecological niches.

What is an example convergent evolution?

Marsupials show multiple examples of convergences with placental mammals