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Darwin Finches (1 Viewer)
- Thread starter Peter Kovalik
- Start date
Mysticete
Well-known member
I am honestly surprised something like this hasn't been previously published.
Sisyphean evolution in Darwin's finches - McKay and Zink 2014
http://onlinelibrary.wiley.com/doi/10.1111/brv.12127/abstract
The trajectory of speciation involves geographic isolation of ancestral populations followed by divergence by natural selection, genetic drift or sexual selection. Once started, the process may experience fits and starts, as sometimes diverging populations intermittently reconnect. In theory populations might cycle between stages of differentiation and never attain species status, a process we refer to as Sisyphean evolution. We argue that the six putative ground finch species (genus Geospiza) of the Galápagos Islands represent a dramatic example of Sisyphean evolution that has been confused with the standard model of speciation. The dynamic environment of the Galápagos, closely spaced islands, and frequent dispersal and introgression have prevented the completion of the speciation process. We suggest that morphological clusters represent locally adapted ecomorphs, which might mimic, and have been confused with, species, but these ecomorphs do not form separate gene pools and are ephemeral in space and time. Thus the pattern of morphological, behavioural and genetic variation supports recognition of a single species of Geospiza, which we suggest should be recognized as Darwin's ground finch (Geospiza magnirostris). We argue that instead of providing an icon of insular speciation and adaptive radiation, which is featured in nearly every textbook on evolutionary biology, Darwin's ground finch represents a potentially more interesting phenomenon, one of transient morphs trapped in an unpredictable cycle of Sisyphean evolution. Instead of revealing details of the origin of species, the mechanisms underlying the transient occurrence of ecomorphs provide one of the best illustrations of the antagonistic effects of natural selection and introgression.
Sisyphean evolution in Darwin's finches - McKay and Zink 2014
http://onlinelibrary.wiley.com/doi/10.1111/brv.12127/abstract
The trajectory of speciation involves geographic isolation of ancestral populations followed by divergence by natural selection, genetic drift or sexual selection. Once started, the process may experience fits and starts, as sometimes diverging populations intermittently reconnect. In theory populations might cycle between stages of differentiation and never attain species status, a process we refer to as Sisyphean evolution. We argue that the six putative ground finch species (genus Geospiza) of the Galápagos Islands represent a dramatic example of Sisyphean evolution that has been confused with the standard model of speciation. The dynamic environment of the Galápagos, closely spaced islands, and frequent dispersal and introgression have prevented the completion of the speciation process. We suggest that morphological clusters represent locally adapted ecomorphs, which might mimic, and have been confused with, species, but these ecomorphs do not form separate gene pools and are ephemeral in space and time. Thus the pattern of morphological, behavioural and genetic variation supports recognition of a single species of Geospiza, which we suggest should be recognized as Darwin's ground finch (Geospiza magnirostris). We argue that instead of providing an icon of insular speciation and adaptive radiation, which is featured in nearly every textbook on evolutionary biology, Darwin's ground finch represents a potentially more interesting phenomenon, one of transient morphs trapped in an unpredictable cycle of Sisyphean evolution. Instead of revealing details of the origin of species, the mechanisms underlying the transient occurrence of ecomorphs provide one of the best illustrations of the antagonistic effects of natural selection and introgression.
Me too. And I really like the name, "Sisyphean".
jurek
Well-known member
Er, how it is different from any other species adapting to local conditions?
And I think, absence of purpose in evolution means that 'partial' 'incipient' or 'incomplete' speciation is the same as 'sisyphean evolution' or 'local adaptation' etc. Evolution has no wish to lead to speciation.
And I think, absence of purpose in evolution means that 'partial' 'incipient' or 'incomplete' speciation is the same as 'sisyphean evolution' or 'local adaptation' etc. Evolution has no wish to lead to speciation.
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Peter C.
...just zis guy, you know?
I don't think it is different from adapting to local conditions. The point here being that in other cases, where gene flow is more restricted, species eventually become genetically incompatible through drift; whereas in the "Sisyphean' case, gene flow is just sufficient to prevent full speciation form occurring. That's how I interpret it.
Indeed, no theoretical breakthroughs here but an interesting re-examination of ground-finch evolution in the Galapagos and the invention of a useful new term for how the "speciation" process sometimes plays out.
Richard Klim
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IOC 26, Tokyo
Ben Sheldon, 18 Aug 2014: Super carved Darwin’s Finch phylogeny on display at registration for #ioc26.
Ben Sheldon, 18 Aug 2014: Super carved Darwin’s Finch phylogeny on display at registration for #ioc26.
mckaybailey
Well-known member
strenua was included in McKay and Zink (2014). It was not distinct in the sense that it did overlap with magnirostris.
Bailey
Bailey
Melanie
Well-known member
Oh, interesting. I wonder that Hume & Walters still considered Darwin's Large Ground finch as extinct but most other sources (including HBW) recognized Geospiza magnirostris as monotypic.
mckaybailey
Well-known member
Maybe I can clarify. Gould (1937), in the first description of Darwin's Finches, originally described magnirostirs and strenua as two different species. They were later merged as one species, the Large-billed Ground-finch (magnirostris had priority, so it retained the scientific name), by most authors. Then strenua, which was confined to only one or two islands, went extinct, leaving magnirostris as monotypic.
I hope this helps.
Bailey
mckaybailey
Well-known member
I would think so. Extinct subspecies appear in Dickerman's world list.
Although, in this case, it's possible that an author might decide not to recognize strenua.
Richard Klim
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Large Ground Finch
But if strenua is not recognised as a valid taxon, then of course magnirostris sensu lato (ie monotypic) remains extant.
Hume & Walters 2012 (Extinct Birds) states the opposite, ie that 'Darwin's Large Ground Finch' magnirostris sensu stricto (Floreana and San Cristóbal) is extinct, but strenua (other islands) is extant.
But if strenua is not recognised as a valid taxon, then of course magnirostris sensu lato (ie monotypic) remains extant.
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mckaybailey
Well-known member
Sorry, this is correct. I knew it was the larger-billed form that went extinct, but I somehow forgot that this larger-billed form was called "magnirostris" :-C. I'll blame it on jet lag from my quick trip to Japan.
Because Darwin didn't record island locality information for the finches, Gould's descriptions can be difficult to match up to current populations, but magnirostris was described as slightly larger than strenua. Again, strenua is not that different (a lot of morphological overlap), and I assume it is not recognized by most.
Sorry for the confusion.
Bailey
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Richard Klim
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Richard Klim
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Richard Klim
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Lamichhaney et al
Lamichhaney, Berglund, Sällman Almén, Maqbool, Grabherr, Martinez-Barrio, Promerová, Rubin, Wang, Zamani, Grant, Grant, Webster & Andersson (in press). Evolution of Darwin's finches and their beaks revealed by genome sequencing. Nature. [abstract & supp info]
Uppsala University, 11 Feb 2015: Evolution of the Darwin's finches and their beaks.
Princeton University, 11 Feb 2015: A gene that shaped the evolution of Darwin's finches.
BBC News, 11 Feb 2015: Genomes reveal Darwin finches' messy family tree.
Lamichhaney, Berglund, Sällman Almén, Maqbool, Grabherr, Martinez-Barrio, Promerová, Rubin, Wang, Zamani, Grant, Grant, Webster & Andersson (in press). Evolution of Darwin's finches and their beaks revealed by genome sequencing. Nature. [abstract & supp info]
Uppsala University, 11 Feb 2015: Evolution of the Darwin's finches and their beaks.
Princeton University, 11 Feb 2015: A gene that shaped the evolution of Darwin's finches.
BBC News, 11 Feb 2015: Genomes reveal Darwin finches' messy family tree.
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Richard Klim
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Well, corresponding author, but not lead author. Let Sangeet Lamichhaney and Jonas Berglund have their moment of fame.
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