Monday, March 26, 2012

Types of Evolution

There are three major types of evolution: adaptive radiation, divergent evolution, and convergent evolution. Some modern species are very good examples of these different forms of evolution.

Adaptive Radiation

Four of the species of finch that can be found on the Galapagos islands
This is usually only seen in island populations and is where a single founding species will evolve to a wide variety of ecological niches. One very famous example of this is Darwin's finches on the Galapagos. It's likely that all of the finches evolved from a small group that somehow drifted to the islands many years ago. Now, the numerous species have adapted to eat virtually anything that can be found on the island. This includes some very clever things, including a species that uses cactus needles to spear insect larvae out of trees. 

Divergent Evolution

A hyrax
An African elephant
This is when two closely related species become quite distinct over time. My personal favorite divergent evolution example involved the elephant and the hyrax. These species appear incredibly different in size, shape, and many other characteristics. However, the two groups are far closer than you would suspect. The hyrax is not very close to the rodents it resembles, but its closest living relative is, in fact, the elephant. There are many other examples, including weasels and the red panda.

Convergent Evolution

This hyrax looks like a rodent
Rock cavies greatly resemble the hyrax
Convergent evolution is when two very distantly related species evolve in a similar habitat and end up appearing quite similar. In line with my last example, the hyrax also shows convergent evolution. Though most closely related to the elephant, these small animals most closely resemble rodents such as the capybara. Closer examination reveals numerous differences, but the resemblance is quite startling. There are many examples of this as well, including two snake genera (one Asian, one American) that are nearly identical.

Sources are PBS, more PBS, and Earlham College. Images are from Wikimedia Commons and are under Creative Commons licenses or are copyright free: one, two, three, four, five.


  1. Lake Malawi cichlids are my favorite example of adaptive radiation. They are thought to have all descended from a common ancestor that came from Lake Tanganyika about a million years ago. Right now there are about 500 different species that all descend from that common ancestor, and they have adapted to so many different niches in the lake that it is really quite amazing.

    1. There are some really good examples of adaptive radiation out there, and that's a great one. I love studying species relationships such as these.

  2. Thank you for choosing the wonderful hyrax for your example. Not enough people know about these lovely creatures...