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Re-lumping of Common & GW Teal (1 Viewer)
- Thread starter fugl
- Start date
Richard Klim
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I assume you are referring to the recent Cornell/Clements Checklist updates.
This simply reflects Cornell's decision to henceforth strictly follow AOU NACC/SACC, which do not split these taxa.
Anas carolinensis is still recognised by (at least) IOC, AERC, BOURC, DB & OSME.
Richard
This simply reflects Cornell's decision to henceforth strictly follow AOU NACC/SACC, which do not split these taxa.
Anas carolinensis is still recognised by (at least) IOC, AERC, BOURC, DB & OSME.
Richard
Ah, I see, that's all it is, thank you. I thought maybe some new research had been published.
Mysticete
Well-known member
IIRC, the reason that the AOU hasn't accepted the split is because Common and GW teal freely hybridize in the Aleutians. I KINDA of think the AOU might be correct on keeping them lumped (although it would be nice if they acknowledged the Mexican Duck split, and god knows that ducks don't tend to be terribly choosy about who/what they mate with).
Thanks for that. I was aware that the split was a controversial in the U. K (where it's "officially" recognized). but I didn't know why. Just another "evolution in action" type situation, I guess.
birdboybowley
Well-known member.....apparently so ;)
That's always the big dichotomy with ducks isn't it?? The reason why they haven't accepted the split is plain dumb - by the same measure then Tufted Duck and Pochard should also be one species...
Gentoo
Guest
I agree with everyone in this thread. But that same rationale, all large white-headed gulls should be one species as well as in one combination or another, they all hybridize.
colonelboris
Right way up again
I subscribe to Jos Stratford's theory - Big Gull, Small Gull, Ross' Gull...
l_raty
laurent raty
There is hybridization and hybridization...
When two taxa coexist broadly in sympatry, hybridize from time to time but nevertheless remain clearly distinct (vast majority of the birds looking 'pure') and do not at all seem to be in the process of merging into a single taxon, you can't treat them as a single species. (Whatever species model you choose to work with.)
When two taxa are mainly allopatric (the teals live on different continents), are in contact in an area that is very small in comparison to their entire range, and hybridize in this area, the interpretation is much more difficult. And indeed the decision to split or lump may be rather arbitrary.
Pochard and Tufted Duck are in no way comparable to the teal case. If you want something a bit more comparable, I'd suggest Baltimore/Bullock's Oriole.
In the case of the Aleutian teal populations, I do not know what 'freely hybridize' means exactly in quantitative terms, and I even think the relevance of this observation could possibly be questioned, even under the BSC. The Aleutians are remote islands. If what happens there is that the local population is only supplied from time to time with birds coming from one or the other direction, these newly arriving birds could simply have no other choice than 'do as the others do' to find a local mate. If so, what is going on there could have very little predictive value for what could happen, should the ranges of the two taxa suddenly come in much broader contact. But on the other hand, it remains true that, if this is the only existing contact zone, this is the only evidence we have at hand to try predicting the outcome of such an event.
When two taxa coexist broadly in sympatry, hybridize from time to time but nevertheless remain clearly distinct (vast majority of the birds looking 'pure') and do not at all seem to be in the process of merging into a single taxon, you can't treat them as a single species. (Whatever species model you choose to work with.)
When two taxa are mainly allopatric (the teals live on different continents), are in contact in an area that is very small in comparison to their entire range, and hybridize in this area, the interpretation is much more difficult. And indeed the decision to split or lump may be rather arbitrary.
Pochard and Tufted Duck are in no way comparable to the teal case. If you want something a bit more comparable, I'd suggest Baltimore/Bullock's Oriole.
In the case of the Aleutian teal populations, I do not know what 'freely hybridize' means exactly in quantitative terms, and I even think the relevance of this observation could possibly be questioned, even under the BSC. The Aleutians are remote islands. If what happens there is that the local population is only supplied from time to time with birds coming from one or the other direction, these newly arriving birds could simply have no other choice than 'do as the others do' to find a local mate. If so, what is going on there could have very little predictive value for what could happen, should the ranges of the two taxa suddenly come in much broader contact. But on the other hand, it remains true that, if this is the only existing contact zone, this is the only evidence we have at hand to try predicting the outcome of such an event.
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Daniel Philippe
Well-known member
What about this tree Laurent ? Is it reliable enough to conclude that carolinensis may not be the closest relative of crecca ?
l_raty
laurent raty
There are two issues here.
One is that this is a gene tree, not a taxon tree, and the taxon tree could be different. It would be vastly better to have this tree complemented with nuclear data, preferably from a few different genes, to see if these show a congruent pattern. With mtDNA only, the conclusion cannot go beyond the fact that the mtDNA of carolinensis may not be the closest relative of the mtDNA of crecca.
The other is that the tree offers no measure of support, so we cannot know to which extent the branching pattern is solid. However:
- This tree shows that the mtDNA of most American A. (crecca), most Eurasian A. (crecca), and most Argentinian A. flavirostris segregate into three distinct clusters (note the single Russian sample among the American samples, though - but of course we don't know how this bird looked).
- There are published analyses, based on other mtDNA genes (cyt-b and ND2; e.g. http://elibrary.unm.edu/sora/Auk/v116n03/p0792-p0805.pdf), that included much fewer birds but showed exactly the same branching pattern, and in these analyses the branching pattern was strongly supported.
Considering these two sources of evidence together, I think it is rather safe to say that the branching pattern, as you see it in the barcode tree, must be solid.
Laurent -
Richard Klim
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Of related interest, Gibson & Byrd 2007 (Birds of the Aleutian Islands, Alaska) includes comprehensive species accounts and an inventory of specimens collected in the Aleutians. It treats the Aleutian subspecies nimia (normally considered a subspecies of A crecca sensu strictu) as a synonym of crecca. The book includes two colour photos of male crecca/carolinensis intergrades: one with both scapular stripe and breast bar; and one with neither scapular stripe nor breast bar.
Nimia is/was recognised by (at least) H&M3, Cornell/Clements, HBW, Madge & Burn 1988 (Wildfowl), BNA, BWP, AERC, & BOURC; but not by Alderfer 2006 (Complete Birds of North America).
Richard
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Even if carolinensis is more closely related to flavirostris (and not crecca), it does not mean that carolinensis and crecca cannot be lumped into one species, and flavirostris put into another species, if your follow the BSC (and a good majority of the AOU-CLC does). Theoretically, two populations (say, A & C) that are very different genetically can be phenotypically identical (thus no reproductive isolation), while it may take only one nucleotide substitution (in population B that has recently split from A) to create a phenotypic difference that leads to reproductive isolation. Thus A & B are more closely related than A & C, but A & C are considered the same species because they are not reproductively isolated, while A/C & B are different species. Many who follow the BSC do not think that monophyly is an absolute critereon at the species level.
Andy Kratter
Andy Kratter
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Daniel Philippe
Well-known member
There was a recent consensus from all SACC members to split Anas andium from A. flavirostris: http://www.museum.lsu.edu/~Remsen/SACCprop356.html
The 3-way merger may not be topical …
l_raty
laurent raty
If you're interested in these, you can check this -
http://web.archive.org/web/20051103...vin_mccracken/reprints/iab-2005-mccracken.pdf
(But it's unpublished... despite not being very recent.)
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Thanks for that-- interesting & thought provoking. All one seems to hear about nowadays--I'm a non-biologist standing outside all this looking in--is cladistics & the various flavors of PSC so it's nice to know that the BSC is still alive & kicking
l_raty
laurent raty
Though I generally don't disagree, I'd suggest you read this :
http://socrates.berkeley.edu/~ccicero/reprints/IOC1999.spconcepts.pdf
(The authors are two current and one former member of the AOU NACC.)
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l_raty
laurent raty
With the recent publication of Kerr et al. 2009, Argentinian bird barcodes - including several barcodes of A. flavirostris - have now been made publicly available. As a result, I can now at least answer this concern. The branching is quite clearly strongly supported.
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