'Time-sharing' tropical birds key to evolutiona...( KINGSTON ON Whereas most birds are ...)

KINGSTON, ON Whereas most birds are sole proprietors of their nests, some tropical species time share together a discovery that helps clear up a 150-year-old evolutionary mystery, says Queens University Biology professor Vicki Friesen.

The Queens-led international study confirms one of Charles Darwins more controversial theories first put forward in 1859 and since disputed by many experts that different species can arise, unhindered, in the same place. Others believe that a geographic barrier such as a mountain or a river is required to produce two separate species. Although focused on how species change over time through natural selection, Darwins landmark book, The Origin of Species, also speculates that it is possible for different species to develop in the same place.

The teams findings will appear this week in the on-line Early Edition of the international journal, Proceedings of the National Academies of Science (PNAS).

With PhD student Andrea Smith and an international team of researchers, Dr. Friesen studied a small seabird called the band-rumped storm petrel, which nests on desert islands in the tropics and sub-tropics. They observed that one set of petrels will breed in burrows, raise their chicks, and leave for the winter. Then a different set of birds moves in similar to a vacation time share and repeats the pattern in the very same burrows. When the season changes again, the first set of birds will return.

Were taught today that new species generally emerge as a result of a geographic barrier such as a mountain range or river, creating two separate populations that cant easily move from one place to the other, says Dr. Friesen, an expert in evolutionary biology. While that model fits for many parts of the natural world, it doesnt explain why some species appear to have evolved separately, within the same location, where there are no geographic barriers to gene flow.

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