This is certainly interesting, but a little historical perspective is in
order. (Do young scientists ever read anything older than 10 years or so?)
This is not a situation discovered by this group. The ring situation in
Phylloscopus trochiloides was described by Ticehurst in 1938 and was
featured by Mayr in his 1942 book Systematics and the Origin of Species.
It's valuable to have these details about the changes in song as the species
was evolving, but the ring of subspecies, defined on morphological grounds,
was already clear. I think the authors make a bit much of their work.

Burt Guttman
The Evergreen State College 360-867-6755
Olympia, WA 98505 guttmanb at evergreen.edu

Reunite Gondwana

> ----------
> From: Eugene Hunn[SMTP:enhunn at Home.com]
> Reply To: enhunn at Home.com
> Sent: Friday, January 19, 2001 6:28 PM
> To: TWEETERS
> Subject: Fw: ring species
>
> >
> > Subject: Fwd: [evol-psych] Biologists uncover Darwin's 'missing
> evidence'
> > for divergence of species in a warbler's song
> >
> > Hey, Wishpush, this is too cool!
> > best--krazykoyote
> > Tweets,
> >
> > FYI.
> >
> > Gene Hunn, enhunn at Home.com, Seattle
> >
> > =======
> > FOR RELEASE: 17 JANUARY 2001 AT 14:00 ET US
> > University of California, San Diego
> >
> > http://www.ucsd.edu/
> >
> > Biologists uncover Darwin's missing evidence for divergence of species
> in
> > a warbler's song
> >
> > Biologists at the University of California, San Diego have demonstrated,
> > in a study of the songs and genetics of a series of interbreeding
> > populations of warblers in central Asia, how one species can diverge
> into
> > two.
> >
> > Their description of the intermediate forms of two reproductively
> isolated
> > populations of songbirds that no longer interbreed is the "missing
> > evidence" that Darwin had hoped to use to support his theory of natural
> > selection, but was never able to find.
> >
> > "One of the largest mysteries remaining in evolutionary biology is
> exactly
> > how one species can gradually diverge into two," says Darren E. Irwin, a
> > biologist at UCSD who headed the study, detailed in the January 18 issue
> > of the journal Nature. "This process, known as speciation, is very
> > difficult to study because it can take a great deal of time to occur."
> >
> > Biologists have generally learned about the divergence of species by
> > comparing many different species at various stages of speciation. But in
> > their study of the greenish warbler, a songbird that breeds in forests
> > throughout much of temperate Asia, Irwin and his colleagues' Trevor D.
> > Price, a biology professor at UCSD, and Staffan Bensch, a former
> > postdoctoral student at UCSD now at Sweden's Lund
> >
> > University discovered a rare situation known to biologists as a "ring
> > species.""Ring species are unique because they present all levels of
> > variation, from small differences between neighboring populations to
> > species-level differences, in a single group of organisms," says Irwin,
> a
> > former student of Price who is in the process of beginning his
> > postdoctoral work with Bensch at Lund University.
> >
> > In the case of the greenish warbler, Phylloscopus trochiloides, the
> > scientists discovered a continuous ring of populations with gradually
> > changing behavioral and genetic characteristics encircling the Tibetan
> > Plateau, which is treeless and uninhabitable. This ring is broken by a
> > species boundary at only one place, in central Siberia, where two forms
> of
> > the songbird coexist without interbreeding.
> >
> > "This creates a paradox in which the two co-existing forms can be
> > considered as two species and as a single species at the same time,"
> says
> > Irwin. "Such ring species are extremely rare, but they are valuable
> > because they can show all of the intermediate steps that occurred during
> > the divergence of one species into two."
> >
> > In their paper, the scientists show how they discovered a gradual
> > variation in the song patterns, morphology and genetic markers of 15
> > populations of the greenish warbler. At each end of the ring of
> > interbreeding populations, which extend around each side of the Tibetan
> > plateau and through the Himalayas, the scientists found that the two
> > distinct, non-interbreeding forms of the bird do not recognize each
> > other's songs, which are critical in the selection of their mates. They
> > determined this from experiments in which they played recordings of male
> > greenish warbler songs and judged the response of other birds in the
> > trees."In the greenish warbler, as in most songbirds, males sing to
> > attract mates and to defend territories," says Irwin. "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 gradually become longer and more
> complex.
> > On the eastern side of the ring, moving northwards through China, songs
> > also become longer and more complex, but the structure is different than
> > on the western side. Where the birds meet in Siberia, their songs are so
> > different that they do not recognize each other as mates or competitors.
> > They act like separate species, and the genetic evidence supports that
> > conclusion.
> >
> > "Apparently, as the birds moved north along two pathways into the
> forests
> > of Siberia, their songs became longer and more complex, perhaps because
> > females in the north rely more strongly on song when choosing a mate.
> But
> > the forms of complexity differed between west and east Siberia, because
> > there are more ways to be complex than simple.
> >
> > "The greenish warbler is the first case in which we can see all the
> steps
> > that occurred in the behavioral divergence of two species from their
> > common ancestor. These results demonstrate how small evolutionary
> changes
> > can lead to the differences that cause reproductive isolation between
> > species, just as Darwin envisioned."
> >
> > The study was financed in part by the National Science Foundation and
> > National Geographic Society.
> > http://www.eurekalert.org/releases/ucsd-bud011601.html
> >
> >
> >
> >
>