-------- Forwarded Message --------
Subject: Re: [BIRDWG01] Western Flycatcher: two species or one?
Date: Sun, 22 Nov 2015 17:53:43 -0800
From: Andrew Rush <ar...@berkeley.edu>
Reply-To: Andrew Rush <ar...@berkeley.edu>
To: birdw...@listserv.ksu.edu
Hello all,
Because I am the primary author on the most recent genetic analysis of
these species (mentioned in the post by Douglas Futuyma cited by Peter
Post), I thought that I could add a little to this discussion. I
recently finished my dissertation research, most of which focused on
these two species. While it is true that the two species are admixed in
their DNA over a large part of the West, the Pacific-slope populations
west of the crest of the Sierra, Cascades, and Coast Ranges (i.e., the
Pacific Slope) remain genetically and phenotypically distinct. We know
that gene flow from interior populations to the west slope Pacific-slope
populations occurs to some extent, but it does not result in widespread
genetic mixing like it does on the east slope. So, it is a little more
complicated than two species just merging (back) into one. Pacific-slope
seems to be merging more into Cordilleran than Cordilleran is merging
into Pacific-slope. I’m not sure taxonomists will take this nuance !
into consideration when deciding what to do with these species, but
from an evolutionary perspective, it is interesting. I will have at
least a couple of more papers on this out soon.
As soon as you cross the crest of the Pacific Slope to the east side,
you encounter mostly genetically intermediate birds with intermediate
songs or calls. There is some proportion of admixed birds in populations
all the way to the Black Hills and to northern Utah and Colorado. On the
other hand, you almost never encounter birds with intermediate songs or
calls on the west side and almost no birds are mixed in their DNA…and
these are limited to areas like Mt. Shasta in California, which is very
close to admixed populations.
So, if you have seen a Cordilleran Flycatcher in southern Colorado, New
Mexico, or Arizona, you are probably safe…in terms of listing. If your
Cordilleran Flycatcher is from Alberta, Idaho, Montana, Wyoming, or the
eastern parts of the coastal states, you have a higher likelihood of
having seen an admixed bird.
One last thing in terms of identifying these species. I have not
formally analyzed the position notes yet (i.e., ‘pee-o-weet’ and
‘weet-seet’) but it seems that these change in a slightly different way
than the songs geographically. I.e., you can encounter birds whose
position note is more purely Cordilleran that has a more intermediate
song type and a more intermediate genotype.
I hope this is interesting to some of you.
Andrew Rush
On Nov 22, 2015, at 5:23 PM, Peter Post <pwp...@nyc.rr.com> wrote:
In light of the recent discussion on "Western Flycatcher" I thought the post by
evolutionary biologist and birder Douglas Futuyma, earlier today on NYS Birds, might be
of interest.
http://birding.aba.org/message.php?mesid=1027591&MLID=NY01&MLNM=New%20York
Peter
Peter Post
New York City
pwp...@nyc.rr.com
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