Look Alikes Aren't Always CopyCats

Dolphins and sharks look alike and live in the ocean, but most people regard them as different types of animals: dolphins are mammals with hair and mammary glands so they are more like us than sharks which have gills and are more like other fish.

Scientists call this phenomenon convergent evolution, and there are examples of it in all forms of life. Bats and birds fly and have wings, cacti and euphorbias have spines and grow in deserts, and koalas and humans have finger prints. These organisms are considered by science to have acquired these traits independently of each other - sometimes in response to similar environments.

For the scientist it can be exciting to identify examples of convergent evolution. However a recent study of giant plants suggests that the designation may be given erroneously if not enough lines of inquiry are pursued.

The giant Lobelia is found globally. Its range includes eastern Africa, the Hawaiian Islands, South America, French Polynesia and southeast Asia. Lobelias are most often found as small, herbaceous plants commonly used as ornamentals. So when the various populations of giant Lobelias were discovered spread across the world, it was assumed that this was an example of convergent evolution: that the herbaceous Lobelia will evolve the giant form in response to particular environments.

Alexandre Antonelli published in BMC Biology that all the giant Lobelias are actually related to each other. Scientists call this a monophyletic group meaning they come from a common ancestor and more importantly the giant form of the plant evolved once and all the giant Lobelias today come from that originating population. Antonelli used molecular analysis to establish this close relationship. He found that the giant Lobelias probably came from eastern Africa between 25 and 33 million years ago.

He concludes his paper stressing that there be careful analysis before making assumptions about morphological development and convergent evolution in all organisms.

Click here to read the original article

copyright 2009 Brendan Craughwell. All rights reserved. SCIENTIFIC STATION is a trademark of Brendan Craughwell. All rights reserved.