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Published online 16 November 2009 | Nature | doi:10.1038/news.2009.1089
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Darwin's finches tracked to reveal evolution in action
A new species of finch may have arisen in the Galapagos.
A husband and wife team has spotted what could be the beginning of a new species of finch on one of the Galapagos Islands, where Charles Darwin developed his ideas about evolution.
Peter and Rosemary Grant, evolutionary biologists at Princeton University in New Jersey, have spent nearly four decades watching finches on Daphne Major, in the Galapagos archipelago where Darwin, too, studied finches.
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Extraordinarily well-documented example of evolutionary pressures that in a relatively short period resulted in the genesis of a new species of finches! Would inbreeding among the 5110 species on Daphne Major result in mutations that might be detrimental to the continuation of his species on Daphne Major? How might one predict an outcome?
Ijaz S. Jamall, Ph.D., DABT
I would like to see some points made clear. The new variety is not due to the appearance of a mutation, but the "appearance" of a bird from a different island, right? So what we have here is a line of hybrids, yes? So even if there is a "speciation event" in the confirmation of reproductive isolation, there is still nothing more going on here than a (probably temporary) separation of a subset within the total gene pool of the finches in the Galapagos. That the new variety is (apparently) intermediate between the smaller medium ground-finches of Daphne Major and the (apparently) larger medium ground-finches of Santa Cruz (let me guess: Santa Cruz is the larger of the two islands?) demonstrates that intermediate types are not necessarily transitional forms, and researchers discovering new varieties or species without observing their history should be careful about that.
Mr. Bump:
My understanding is that you do not need a mutation to form a new species. Reproductive isolation by geography or behavioral traits or other means is the first step. Over time, assuming reproductive isolation is maintained, the isolated population will accumulate small mutations in their overall genome that, at some undefined time, will make reproduction with the parent population genetically impossible under any circumstances (natural or otherwise).
Whether or not the new species looks substantially different from the parent population depends on the selection pressures (natural or sexual) faced by the isolated population. If they specialize in some new food or new habitat, their bodies will gradually evolve to be better adapted to the new life style. If females decide that blue is the new brown, perhaps (if the finch genome has was it takes) the males will gradually turn blue. If the selection pressures are not that different from those faced by the host population, the new species may end up looking pretty similar to the parent population.
The main role of mutations is, as far as I understand it, to provide the natural more or less random variation among individuals that we see every day. It is this variation that selection pressures work on.