Evolution in Action

Researchers have found what they believe to be a speciation event occurring in two populations of small birds called the Monarch flycatcher. The two separate populations live on different islands, so there is a natural barrier which, if maintained long enough, leads to a branching in the tree of life. One group lives on the large island of Makira, part of the Solomon Islands. The other lives on smaller, surrounding islands, and it is this group that developed one small mutation to a gene that regulates the production of melanin which, for birds, determines the color of their feathers. In this case, the normally black birds on the surrounding islands developed a brownish underbelly.

According to the PhysOrg article Study catches two bird populations as they split into seperate species,

The question of whether these two populations are on the road to speciation comes down to sex. When two populations stop exchanging genes--that is, stop mating with each other—then they can be considered distinct species.

While they can't actually observer every encounter between the two populations to check for mating, male birds are notorious for defending their territory from others males that are potential sexual competitors. The Makira population was seen to not really mind if the brown-bellies came around, which leads the researchers to think they are not seen as much of a threat.

Of course, this doesn't prove anything conclusively...only time can really tell. Over the next hundred years or so, the natural barrier may not be big enough to keep the mutated gene from spreading to all flycatchers, which means no speciation. Still, this is an example of evolution in action, whether or not speciation occurs. Can you guess why?

See Elie Dolgin's post at TheScientist.com for more, including comparison images.