Tropical bird species evolved without isolation: study
Evolutionary theorist Charles Darwin had it right when he said different species could develop in the same place, a new Canadian-led study suggests.
Darwin's theory of sympatric speciation — distinct speciesevolvingfrom a single parent species within a geographic area — first appeared in his 1859 book The Origin of Species. He was not able to prove it, and the dominant theory since has been allopatric speciation —that a barrier, such as a mountain, glacier or ocean, is required to produce separate species.
Now, 148 years later, research led by Queen's University in Kingston, Ont., may prove the existence of sympatric speciation. The international research team found that this type of evolution could occur by "allochronic isolation," or separation by breeding times.
Prior to the study, released this week in the journal Proceedings of the National Academies of Science, there were only two documented cases of species evolving in the same place and no clear evidence as to how it would occur in nature.
The research team studied a species of tropicalseabird known as the Madeiran or the band-rumped storm petrel,which populatearchipelagos in the tropic and sub-tropic, and have different breeding seasons. Some colonies have a single breeding season, othersprolonged seasons, and in five locations, there are two distinct breeding seasons.Theresearch focused on the latter five areas.
Researcher Andrea Smith told CBC News the team was interested in whether the difference in breeding periods "was a barrier to drive them to become separate species."
By analyzing genetic variation in the species, they found the petrel populations differed genetically in all five locations and had ceased to exchange genes in two.
"The seasonal populations from four of the locations are more closely related to each other than populations from the same breeding seasons elsewhere," said Smith, suggesting that "one arose from the other just out of the separation of breeding."
The study says this finding suggests that "seasonal populations appear to have arisen sympatrically at least four times." Additionally, they found that the species had not interbred for between 1,000 to 180,000 years.
"I think it's exciting for a number of reasons," said Smith. "One is that it's challenging the idea that you need a geographic barrier for species to arrive."
She said the findings also suggest that this mode of speciation might be more common than researchers had previously thought.
Smithsaid their discovery couldleadto changes in species protection.
"In finding that there are actually populations that are considered separate species, it indicates that we need to be looking into conservation for these species, because a lot of them are represented only by a couple hundred birds," she explained. "We don't want to lose that biodiversity that we've documented."
- In five locations, the tropical seabird known as the Madeiran has two distinct breeding seasons. An earlier version of the story incorrectly reported there were periods when there was no breeding at all.Nov 14, 2007 10:00 AM ET