New bird species can arise in two generations

General birdwatching discussion, help with bird identification, and all other things relating to wild birds and birding in NZ that don't fit in one of the other forums.
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Liam Ballard
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Re: New bird species can arise in two generations

Postby Liam Ballard » Tue Nov 28, 2017 5:01 pm

The part at the end made me smile - "Charles Darwin would be excited to read this paper..."
Correct me if I am wrong, but didn't he famously say "Natura de facit saltum" or Nature does not jump...
Of course perhaps he would he happy to be proven wrong.
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David Riddell
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Re: New bird species can arise in two generations

Postby David Riddell » Wed Nov 29, 2017 11:18 am

The Latin phrase Natura non facit saltum predates Darwin by several centuries - Leibniz used it, among others. But Darwin did use the expression several times in The Origin of Species. For example:
As natural selection acts solely by accumulating slight, successive, favourable variations, it can produce no great or sudden modification; it can act only by very short and slow steps. Hence the canon of "Natura non facit saltum," which every fresh addition to our knowledge tends to make more strictly correct, is on this theory simply intelligible.

I'm not sure Darwin would have recognised the appearance of a new Galapagos finch, only slightly different from the other species in its genus with which it shares its island, as a jump. It's more in the form of, in his words, a very short step, even if not a slow one. If we had seen the sudden appearance of a bird that was radically different - something that could not be placed in the genus Geospiza, perhaps something like the warbler finch (Certhidea olivacea) - that would have been something Darwin would have found much more surprising.
We now know, as Darwin didn't, that genetic information is particulate, so changes in it are going to involve jumps, albeit mostly very small ones - the big ones tend not to be successful and are winnowed out by natural selection, just as Darwin suggested.
http://darwin-online.org.uk/content/fra ... wtype=text
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Liam Ballard
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Re: New bird species can arise in two generations

Postby Liam Ballard » Wed Nov 29, 2017 11:56 am

Interesting.... Clearly I need to brush up on my evolutionary biology. So it is then conceivable that the New Zealand Mallard (Anas novaseelandae) (yes I just made that up!) could have arisen within a few years of Mallard x Grey Duck hybridisation given the right conditions?
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Michael
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Re: New bird species can arise in two generations

Postby Michael » Wed Nov 29, 2017 3:13 pm

Liam Ballard wrote:Interesting.... Clearly I need to brush up on my evolutionary biology. So it is then conceivable that the New Zealand Mallard (Anas novaseelandae) (yes I just made that up!) could have arisen within a few years of Mallard x Grey Duck hybridisation given the right conditions?


From what I understand from this paper, the reason for the quick jump in this Galapagos finch occurred so fast as the offspring were all forced to breed amongst each other due to the song distinctions, thus "strengthening the genes". Mallards and greys are the result of many thousands of birds leading to the genes being extremely mixed, and they are at no liability to mate with another hybrid. I presume we'd need all of the populations to be a mix and breeding together for long enough that a clear phenotype for the species emerges rather than the current mismatch of shabby birds we all know and love.

That's my take on it, though I could be misinterpreting :D
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David Riddell
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Re: New bird species can arise in two generations

Postby David Riddell » Thu Nov 30, 2017 7:55 am

I think you've got that about right Michael. Ducks are nowhere near as discerning when it comes to mating, and certainly in the case of greys and mallards differences in calls/songs play virtually no role in isolating the two species from each other.

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