Joined: Sep. 2002
|Quote (RDK @ Nov. 09 2009,21:15)|
|Quote (Zachriel @ Nov. 09 2009,20:45)|
|Joseph: All the finches on the Galapagos Islands are considered one species.|
No. They're not. Darwin didn't even recognize them all as finches. They were originally determined to be separate species of finch by John Gould in 1837, and they've been considered separate species ever since.
Grant & Grant: The adaptive radiation of Darwin's finches in the Galapagos archipelago stands as a model of species multiplication. The radiation began two to three million years ago, and resulted in 14 species being derived from the original colonizing species ...The role of natural selection and adaptation to feeding niches in the allopatric phase of speciation has been demonstrated repeatedly, Annals of the Missouri Botanical Garden 2006.
Sato et al., Darwin's finches comprise a group of 15 species endemic to the Galápagos (14 species) and Cocos (1 species) Islands in the Pacific Ocean. The group is monophyletic and originated from an ancestral species that reached the Galápagos Archipelago from Central or South America, Molecular Biology and Evolution 2001.
Gould, Birds: Part 3 of The zoology of the voyage of H.M.S. Beagle, 1841.
BUT IT'S STILL A BIRD!!11!!!
Don't you see, Zach? It's still of the bird species. That finch will never be a dog; it will always be a bird.
Edit: Whoa. Something rotten in the water supply over at UD? And I mean more than usual, because O'Leary's latest post is some mighty strong Tard.
Jerry is simply obsessing on the idea that many of the populations in the Galapagos hybridize, albeit rarely. Therefore they have to be of the same species.
An interesting fact (which jerry also seems dazzled by) is, birds as a group tend to develop genetic incompatibility (hybrid sterility) as a form of reproductive isolation much more slowly than with other groups, like mammals, by a factor of about 10. It's not clear why that is so-- the reason may be develpomental. So avian species possess a large capoacity for hybridization between species.
Why this is of such interest to jerry is beyond my simple mind. What is obvious in birds is, they do maintain enough reproductive isolation (geographic, ecological, etc)to develp not only an astonishing diversity, but enough to keep those diverse populations relatively stable enough for us to recognize and think of them as separate species without having to resort to artificial selection to keep them that way. This means the actual level of hybridization is not high enough to disrupt the diversification. The fact they make take longer to develop hybrid sterility is truly irrelevant.
Those who know the truth are not equal to those who love it-- Confucius