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Auteur Topic: Branta leucopsis x canadensis /hutchinsii  (gelezen 201 keer)

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gjcaspers

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Branta leucopsis x canadensis /hutchinsii
« Reactie #1 Gepost op: oktober 05, 2007, 17:18:19 pm »

Since about nine years, there are Branta leucopsis x canadensis hybrids around here (Cuijk/Mook). The F1 hybrids always have some white on the forehead, and a distinct black-brown breast shield. In more recent years, some of these minima-like birds, like in the photos, have been turning up here, but they always have a colour difference between a darker breast and a lighter flank. I take these to be F2 hybrids of Branta leucopsis x canadensis.

The F1 hybrids do reproduce here, inter se as well as with both parent species. However, I have never been able to follow the fate of the goslings, after the families join the big flock of some 300 B. canadensis. So I am not really sure how F2 and R1 hybrids should look. I have no experience with Branta leucopsis x hutchinsii hybrids.

With all this hybridizing going on, maybe we should follow the biological species concept and lump the whole lot. From now on, I'll call Barnacle Goose Anser (Branta) canadensis leucopsis  ;)

 
Gelogd
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Gert-Jan Caspers

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Branta leucopsis x canadensis /hutchinsii
« Reactie #2 Gepost op: oktober 05, 2007, 17:52:14 pm »

You have to check which name is older and thus has priority. If you add the author and the year of description it becomes clear which name has priority: Branta leucopsis (Bechstein, 1803), and Branta canadensis (Linaeus, 1758). So if you want to lump these taxa the name Branta canadensis has priority over Branta leucopsis. Just adding them up as a new "species name" is against the international code of zoological nomenclature.

However, there is another article in the code that also applies here: no scientific names are given to taxa which have a hybrid origin (this is very different frrom botanical nomenclature).

So if you see these geese taxa as two species, the consequence is that there can be no valid scientific name for the hybrids, other than Branta sp.

However, if you see Canadian and barnacle as varieties of one species, B. canadensis is the correct scientific name for both. And you could then consider leucopsis as a subspecies of B. canadensis. So B. c. leucopsis becomes the valid name of the barnacle goose subspecies but not for hybrids!

We can go one step further: both geese taxa were originally described as members of the genus Anas (not Anser, which was established later!), as were most other waterbirds at that time. I know some creationist' biologists that would agree wholeheartily with this suggestion. It fits very well with the concept of "created units" of which "waterfowl" is certainly one. However, the trend is to give each separable taxon a different scientific name (=splitting) and leucopsis is certainly more different that each of the American Branta differ from each other. Also you still have to consider the status of Hawaian goose in this species complex.

What we do here on waarneming.nl (B. canadensis x B. leucopsis) has absolutely no basis in zoological nomenclature but is based on a freely (and incorrectly) used article from botanical nomenclature!

For now I would not bother too much, the vast majority of these geese taxa still evolve separately and only some flocks in some corners of the world hybridise freely. They are completely valid taxa in the phylogenetic species concept (but perhaps not in the less used biological species concept - less used in ornithology that is).

Or am I reacting way to serious on this?
« Laatst bewerkt op: oktober 05, 2007, 17:53:18 pm door tekenaar »
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Paul Veenvliet

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gjcaspers

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Branta leucopsis x canadensis /hutchinsii
« Reactie #3 Gepost op: oktober 05, 2007, 19:14:28 pm »

Citaat
You have to check which name is older and thus has priority. If you add the author and the year of description it becomes clear which name has priority: Branta leucopsis (Bechstein, 1803), and Branta canadensis (Linaeus, 1758). So if you want to lump these taxa the name Branta canadensis has priority over Branta leucopsis. Just adding them up as a new "species name" is against the international code of zoological nomenclature.

However, there is another article in the code that also applies here: no scientific names are given to taxa which have a hybrid origin (this is very different frrom botanical nomenclature).

So if you see these geese taxa as two species, the consequence is that there can be no valid scientific name for the hybrids, other than Branta sp.

However, if you see Canadian and barnacle as varieties of one species, B. canadensis is the correct scientific name for both. And you could then consider leucopsis as a subspecies of B. canadensis. So B. c. leucopsis becomes the valid name of the barnacle goose subspecies but not for hybrids!

We can go one step further: both geese taxa were originally described as members of the genus Anas (not Anser, which was established later!), as were most other waterbirds at that time. I know some creationist' biologists that would agree wholeheartily with this suggestion. It fits very well with the concept of "created units" of which "waterfowl" is certainly one. However, the trend is to give each separable taxon a different scientific name (=splitting) and leucopsis is certainly more different that each of the American Branta differ from each other. Also you still have to consider the status of Hawaian goose in this species complex.

What we do here on waarneming.nl (B. canadensis x B. leucopsis) has absolutely no basis in zoological nomenclature but is based on a freely (and incorrectly) used article from botanical nomenclature!

For now I would not bother too much, the vast majority of these geese taxa still evolve separately and only some flocks in some corners of the world hybridise freely. They are completely valid taxa in the phylogenetic species concept (but perhaps not in the less used biological species concept - less used in ornithology that is).

Or am I reacting way to serious on this?
Yes, you are reacting way too seriously, and yes, I know the name B. canadensis has priority over B. leucopsis, and yes, I would like to see B. leucopsis as a subspecies of B. canadensis.

B. leucopsis may be closer related to B. hutchinsii than B. hutchinsii is to B. canadensis. If you lump these taxa, Hawaiian Goose would have to be included, too. See:
Paxinos EE, James HF, Olson SL, Sorenson MD, Jackson J, Fleischer RC.
mtDNA from fossils reveals a radiation of Hawaiian geese recently derived from the Canada goose (Branta canadensis).
Proc Natl Acad Sci U S A. 2002 Feb 5;99(3):1399-404.

And yes, I know that creationists would like to see only one "kind" of waterfowl, and no, I am not one of them. It's just that with the ease that Anser and Branta species hybridize, one genus of geese would be sufficient in my opinion, with subgenera for the grey and the black geese.

Next point of discussion: do creationists consider Mandarin Duck to be a "kind" of its own, separate from all other waterfowl? ;)  
Gelogd
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Gert-Jan Caspers

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Branta leucopsis x canadensis /hutchinsii
« Reactie #4 Gepost op: oktober 06, 2007, 09:38:36 am »

I feel that the division between Anser and Branta is a valid one because hybrids between these two genera tend to be sterile (as yet I still have to hear about the first proven fertile hybrid between these two genera. They certainly incubate eggs but if they hatch they are not their own!). At the same time hybrids within the same genus are fertile. This indicates that species within each genus are are probably more closely related to each other than to the species of the other genus, so both genera are valid groups within the geese. As a genus is defined as the first grouping above the species level, I favour these as different genera (and I think that the creationists' "kind" could many times be seen as the taxonomists' "family" level).

The other solution is to lump all Anser as one species and all Branta as one species within the genus Anas but then also all ducks as one single species to be consistent. That would go against the biological species concept as many duck taxa co-occur and usually don't hybridise (indicating behavioural barriers against hybridisation, which is sufficient to regard them as separate specues under any species concept).

Ans I am neither creationonist nor evolutionist, I am too busy with current life forms and can't decide who should be more correct. Both are interesting ideas though.

About mandarin: i agree that it is an interesting case, but can't forget how similar it is to American wood duck.
« Laatst bewerkt op: oktober 06, 2007, 09:39:14 am door tekenaar »
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Paul Veenvliet

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Alcedo atthis

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Branta leucopsis x canadensis /hutchinsii
« Reactie #5 Gepost op: oktober 08, 2007, 10:54:44 am »

Sorry, maybe i didn't make myself clear in the beginning...It was not my intention to start a taxonomic discussion ... just in short:
as all this taxonomy is a man-made tool to distinguish between animals, this is bound to cause some problems.

I just wanted to draw attention to this: that very many birds reported as minima in fact seem to be hybrids!

 
Gelogd
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Jörn Lehmhus

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Branta leucopsis x canadensis /hutchinsii
« Reactie #6 Gepost op: oktober 13, 2007, 20:59:02 pm »

well, birds on photo's 1, 2, 4, 12 and 13 appear to have a trace of a dark brest, which would, in my view, indicate that they are hybrids. With all unknown backcrosses we are bound to end up with more and more "unclear" birds and hybrid individuals which look almost entirely like one of the parental (sub) species.

For how many hybrids is it clear that really only one "Canadian" taxon is involved in the parentage? When both (presumed) parents are walking next to them, maybe (but gees are known to dump eggs in nests of other geese: the young they raise don't have to be their own!).

Honestly, I am not sure how to treat these in the database. One "lumped taxon" "Branta-hybrids" maybe? And which Dutch name should we give them? "zwarte-gans hybride" doesn't sound good and no-one knows what I mean with that.
« Laatst bewerkt op: oktober 13, 2007, 20:59:24 pm door tekenaar »
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Paul Veenvliet

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Branta leucopsis x canadensis /hutchinsii
« Reactie #7 Gepost op: oktober 14, 2007, 09:06:55 am »

Citaat
Honestly, I am not sure how to treat these in the database. One "lumped taxon" "Branta-hybrids" maybe? And which Dutch name should we give them? "zwarte-gans hybride" doesn't sound good and no-one knows what I mean with that.
Just Branta-hybrids
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Frank van der Meer

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Branta leucopsis x canadensis /hutchinsii
« Reactie #8 Gepost op: oktober 17, 2007, 13:15:22 pm »

Branta -hybrids sounds a good idea


I also posted these links on birdforum and received some answers; with an experienced North american birder seeing the bird in picture 1  as a Branta hutchinsii (probably minima), as minima can have a darker brownish breast, and some other races too  (I found some on the web which are as extreme as this bird 1, so he is probably right).
however he thought all other birds doo look somehow odd to him and being probably hybrids, but he also agreed that ID from single photos  often is near impossible.

so I tend to give up here....

I guess it would be possible to produce a hutchinsii by hybridising canadensis x leucopsis over some generations...
Gelogd
greetings,
Jörn Lehmhus
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