Hi all
Some more thoughts on a very intriguing subject, it was an interesting
article.
Google: evolution rapid finches
There are many examples of such minor changes in bird populations
being
cited as evidence for observable evolution, including melanotic
urban rock
doves. Darwin hypothesised that the development of all species was
due to
the gradual accumulation of just such minor variations over very long
periods of time. He also investigated at length the inheritance of
variation
in domestic animals including dogs. He didn't have any knowledge
though of
how novel variations appeared. He would have revelled I think in
modern
genetics - rearrangement of genes, mutation of DNA and pondering of
the
possible role of all that "junk" in controlling and changing gene
expression.
"Species" is of course an arbitrary division of a continuous, if
mostly
extinct, chain of variation, with more than one definition to choose
from -
the old one of genetic isolation certainly doesn't work very well,
many
"species" hybridize and produce fertile offspring. In the example
discussed
it is entirely reasonable to suppose we are seeing the first
discernable
link in this chain - we're just not going to be around nearly long
enough
to observe separation into "species". If we had observed this
process in
warblers, would we yet recognise as speciated the Willow Warbler and
the
Chiff Chaff, of for that matter the Northern, Mangrove and Grey
fantails?
The recent ABC Catalyst on Gouldian's certainly set me thinking. It
discussed the strong tendency of Red heads to select Red heads as
mates with
subsequent increased breeding success. The explanation offered was of
previous geographical isolation and merging of diverged populations
when the
climate changed. It certainly suggests early speciation and raises the
possibility of continued now sympatric speciation within actual
flocks. Who
knows, if they survive another million years of climate change there
might
be an additional "tick" to wait for.
Cheers
Andrew Bell
-----Original Message-----
From:
On Behalf Of Peter Shute
Sent: Monday, 7 December 2009 8:24 AM
To: ;
Cc: ;
Subject: Re: [Birding-Aus] Backyard birdfeeders driving avian
evolution
I don't know much about genetics, but I was wondering the same thing
(I
think).
Dogs have been selectively bred till we have an astonishing range of
breeds
of varying sizes and traits, that breed true. Yet I'm told if you
let them
inter breed they quickly revert back to something like their
ancestors.
I've never heard of this being offered as an example of evolution.
Peter Shute
--------------------------
Sent using BlackBerry
