As David Tyler writes over at Access Research Network:
Introgressive hybridization and the Galapagos finches
A branching pattern of variation was central to Darwin’s concept of speciation. As one population of organisms follows one trajectory, another population may spin off in a different direction. When they are sufficiently far apart, they are considered to be separate species. The Galapagos finches have been regarded as exemplars of Darwinian transformation, even leading to the claim that one newly developed population is “behaving as a separate species”. However, the most recent study, from one of the smaller islands (Floreana), concludes that the most likely cause of the disappearance of one of these species is hybridization.
“The authors suggest that hybridization may have been responsible for the disappearance of the large tree finch from Floreana, and that it may now be causing the remaining two species to fuse into one: speciation in reverse.” More.
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4 Replies to “Seems not even Darwin’s finches are sacred”
If you read Jonathan Weiner’s book, The Beak of the Finch, hybridization plays a very prominent role in how the book ends. It was written in the mid-90’s. Hybridization affecting finch populations in the Galapagos has been known for a long time. The “Grants” have written books and articles which, I believe, don’t acknowledge any of this. It is only this month, perhaps in the face of the article David Tyler links to, where the Grants now talk about such ‘hybridization.’
In Weiner’s book, it is a really quite fascinating account of how real, quantitative work is done in the wild, the immense work and dedication it takes, and the kind of technical innovations that are needed to do substantial research among wild populations. It’s quite impressive. At first.
Then, the whole tone of the book changes. Whereas the first half of the book is marked by a kind of scientific triumphalism—wherein Darwinism seems to be there, right in front of our eyes, ready to be seen by all, the second half of the book has a very different tome. Quite somber. And, then, finally, after a season or two of very high rainfall (previously, ‘speciation’ seemed to be happening within view of experimenters during preceding drought years), voila! the experimenters see ‘hybridization’ take place. Completely unexpected. And what happened? A ‘large’ and a ‘small’ species interbred (they had not previously) and a ‘hybrid’,
‘mid-size’ species was coming to dominate the finch population on the island they studied.
This most recent study is on a different island, but with the very same—the very same—kind of result.
Darwin insisted on sterility between species. My guess is that it was the only way of protecting his theory against what is now being documented.
PAV Wrote: “If you read Jonathan Weiner’s book, The Beak of the Finch, hybridization plays a very prominent role in how the book ends…”
As an initiate could you give me a quick definition of Hybridization vs Speciation? Are not two hybrids normally considered to be incapable of breeding? Though in the case of these finches …
Speciation, (being the useless word that it is), in this case simply means that the finches are temporarily reproductively isolated. (A much better term would just be “population splitting”) … and this leads to separate gene pools that have varied expression of the same traits found in all populations. (head/beak morphology)
All hybridization means is that different populations began interbreeding again.. really no different than if a population of humans went to live on another continent for several generations, then came back to mix in with the homeland population again….
How a fanciful, mystical Darwinian evolution fairy-tale still gets wrapped around the cyclic finches is beyond me.
lifepsy wrote: “…How a fanciful, mystical Darwinian evolution fairy-tale still gets wrapped around the cyclic finches is beyond me.”
Thanks for the definition of terms; and yes one wonders how so much about Darwin’s Finches is made out of so little?
And another question, a general one, if I may: As being very new here, if I have a question or point on an off topic or different topic subject, what is the accepted form of introduction?