Subject: [Tweeters] Gene's query about gulls
Date: Feb 22 13:34:34 2009
From: Dennis Paulson - dennispaulson at comcast.net


I should add to the discussion that DNA studies aren't always the
last word, and I'm with Gene in being shocked by these two
conclusions. I see now that he has responded at some length to Hal's
comments.

I reviewed a paper years ago in which DNA analysis showed
conclusively that Wilson's Phalarope wasn't a phalarope. It was just
plain wrong, as subsequent studies showed, but the paper might have
been published as it was if another reviewer also hadn't questioned
the conclusions. And the AOU Checklist committee might have stuck the
Wilson's in with the tringine sandpipers (yellowlegs and their
relatives), puzzling us all, until subsequent studies suggested that
it belonged back with the other phalaropes.

It's quite counterintuitive to me to think that the two yellowlegs
are not each other's closest relative, as they are alike in so very
many ways. This would either imply convergent evolution of the two
yellowlegs from different ancestors or that they are indeed related
but that one of them is the sister species of the very different
Willet. This is not impossible, just seems very unlikely. I will have
to go back and reread the Pereira & Baker paper in the Condor in
which these conclusions were reached. From genetic evidence, they
concluded that both Willet and tattlers were in the genus Tringa
rather than in their own genera, not surprising, but I don't recall
if they gave reasons for the exact order of the list.

It's also hard to imagine that Western and Yellow-footed Gulls are
more closely related to Ring-billed or California than they are to
Glaucous-winged and the other large gulls. I'm not speaking with much
authority here, as I haven't seen the paper by Pons et al. that Hal
mentions. But as Gene wrote, there is other evidence that speaks
against this genetic evidence, and that must be taken into account.

I can certainly see the generic splitting that has been recommended,
with several species taken out of Larus. Laughing and Franklin's Gull
are now in the genus Leucophaeus, Bonaparte's and Black-headed in
Chroicocephalus, and Little in Hydrocoloeus. Interestingly, Pons et
al. proposed also putting Ross's Gull (now Rhodostethia rosea) in the
genus Hydrocoloeus, but the AOU Checklist committee did not accept
that change.

There is always a problem in expressing phylogeny (evolutionary
relationships within a group) in a list. Phylogenies show a series of
branches, and a list merely goes out one branch, then comes back and
goes out another branch. So two species in a row aren't necessarily
considered each other's closest relative. One branch may contain
species 1, 2, and 3, then you have to go back and species 4 came from
the same immediate ancestor as species 1, so it is closer to species
1 than it is to species 3. This happens again and again in longer
lists of species. In many of our lists and field guides, Rock Pigeon
comes right after Tufted Puffin, and no one ever thought they were
closely related. Pigeons are on another branch, far from the branch
that ends in alcids.

I think Bullock's and Baltimore Orioles were lumped on the basis of
their frequent hybridization, not any genetic evidence. They were
then split again based on the fact that this hybridization was
sufficiently infrequent that there was probably substantial
reproductive isolation between the two. This would then just be a
different interpretation of the existing information or additional
field work that provided better information. Later genetic studies
showed (f they are to be believed) that Baltimore and Bullock's
aren't each other's closest relatives.

Question authority! That goes for science as well as everything else.
The great thing is that that is exactly how science is supposed to
work, unlike many of our institutions.
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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