Re: Now They're Singing a Different Song

From: Aaron Agassi (agassi@erols.com)
Date: Fri Jan 19 2001 - 04:25:39 GMT

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    From: "Aaron Agassi" <agassi@erols.com>
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    Subject: Re: Now They're Singing a Different Song
    Date: Thu, 18 Jan 2001 23:25:39 -0500
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    Yes, but does this help to explain any Memetic equivalent?

    ----- Original Message -----
    From: "Wade T.Smith" <wade_smith@harvard.edu>
    To: "Memetics Discussion List" <memetics@mmu.ac.uk>
    Sent: Thursday, January 18, 2001 10:56 PM
    Subject: Fwd: Now They're Singing a Different Song

    >
    > ---------------- Begin Forwarded Message ----------------
    >
    > >From the BBC at:
    >
    > <http://news.bbc.co.uk/hi/english/sci/tech/newsid_1123000/1123973.stm>
    >
    > Songbird shows how evolution works
    >
    > By BBC News Online science editor Dr David Whitehouse
    >
    > Scientists may be witnessing one of the fundamental forces of evolution:
    > the
    > divergence of one species into two.
    >
    > One of the largest mysteries remaining in evolutionary biology is exactly
    > how one species can gradually diverge into two
    >
    > Darren Irwin, UCSD
    >
    > It is the evidence that the originator of the theory of evolution, Charles
    > Darwin, wanted to see but was never able to find.
    >
    > The new data comes from the songs of the greenish warbler, a bird that
    > lives
    > in the foothills of the Himalayas. Researchers have noticed that its song
    > changes gradually throughout its territory.
    >
    > At the extreme ranges of its habitat, the greenish warbler will sing very
    > different songs. This means that although the birds belong to the same
    > species, they will not mate. And eventually, they will become two separate
    > species
    >
    > One becomes two
    >
    > Biologists are saying that this shows how one species can become two, a
    > process known as speciation.
    >
    > "One of the largest mysteries remaining in evolutionary biology is exactly
    > how one species can gradually diverge into two," says Darren Irwin of the
    > University of California, San Diego, US.
    >
    > The Himalayan warblers are an example of a rare condition known as a "ring
    > species".
    >
    > "Ring species are unique because they present all levels of variation,
    > from
    > small differences between neighbouring populations to species-level
    > differences in a single group of organisms," says Irwin.
    >
    > Defending territories
    >
    > The greenish warbler (Phylloscopus trochiloides) lives in a ring-shaped
    > region around the Himalayas with gradually changing behavioural and
    > genetic
    > characteristics. The ring is broken in one place, in central Siberia,
    > where
    > two forms of the songbird exist.
    >
    > "This creates a paradox in which two co-existing forms of the songbird can
    > be considered as two species and as a single species at the same time,"
    > remarks Irwin.
    >
    > "Ring species are valuable because they can show all of the intermediate
    > steps that occur during the divergence of one species into two. In the
    > greenish warbler, as in most songbirds, males sing to attract mates and to
    > defend territories.
    >
    > "The greenish warblers living in the Himalayas sing songs that are simple,
    > short and repetitive. As you go north along the western side of Tibet,
    > moving through central Asia, the songs become longer and more complex,"
    > says
    > Irwin.
    >
    > Recorded songs
    >
    > Irwin and his co-researchers publish their study of the bird in the
    > journal
    > Nature.
    >
    > In their paper, they describe how when recordings of songs were played to
    > warblers which sang differently, the birds did not recognise them - and so
    > would not breed.
    >
    > "The greenish warbler is the first case in which we can see all the steps
    > that occurred in the behavioural divergence of two species from their
    > common
    > ancestor," says Irwin.
    >
    > "These results demonstrate how small evolutionary changes can lead to
    > differences that cause reproductive isolation between species, just as
    > Darwin envisioned."
    >
    >
    > ----------------- End Forwarded Message -----------------
    >

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