really strange ducks (3 Viewers)

[Joern Lehmhus]

Hi Michael and all others interested,
Found some more info concerning Aix hybrids at this site.

http://212.187.155.84/wnv/Subdirect...galericulata/Aix_galericulata.html#Aviculture

There are some interesting informations under Aviculture Information (Captive Management).
On Mandarin hybridization they say:
· Pairing with Aix sponsa – Wood duck has been reported but eggs were infertile; there have been no confirmed hybrids. N.B. these ducks have a different chromosome number from other waterfowl; hybridisation appears to be impossible.
On Wood duck hybridization they say
· These ducks (Aix sponsa – Wood duck) are promiscuous and hybridisation is common, particularly with Netta rufina – Red-crested pochard and Aythya ferina – Common pochard drakes.

What do you think, could those two possibilities be these hybrid combinations?

Joern

 

[Michael Frankis]

Hi Joern,

I suppose the first one could be Netta rufina x Aix sponsa, but I don't know enough about hybrid ducks to commit myself.

Thanks for the info on the reasons for the lack of Aix hybrids, I'm surprised no-one has shoved them in different genera yet.

Michael

 

[Joern Lehmhus]

Hi Michael, during Lorenz working time with ducks, somebody, not Konrad Lorenz, actually did a split, I think (Aix galericulata and Lampronessa sponsa).
Lorenz as well as others, was not happy with that. He said allthough there are some differences in the display of the drakes, most other aspects of the behaviour are very similar.

I was looking for more information about this "different chromosome number thingy", but I did not find more on those two species.
But in general, different chromosome numbers can stop interbreeding, because of problems with the different parental chromosome numbers occurring during mitosis, resulting in the embryos death. In other cases it only happens one generation later with the hybrid offspring being sterile, due to problems in the meiosis.
Genetically such species can still be very close, having very similar genes.
Hope, I got this understandable in English , but I think that might be a reason for two species being genetically very close and still not having offspring. One easily forgets that genes and Chromosomes are two different things.

Joern

 

[Charles Harper]

Your English is fine but-- Huh? For genotypic similarity don't the genes have to be in similar positions on equivalent chromosomes?

 

[Joern Lehmhus]

Hi Charles,

that is not nessesarily so; due to crossing overs and due to situations where two different chromosomes are combined to a bigger one. Thats how the different chromosome numbers in different species of Drosophila flies happened, for example. But whereas crossing overs are a common occurence, that other thing is not so common.
One slightly different example in humans is that one of the two chromosome 14, I think it was, and one of the two chromosome 21 can stick together with the ends. Then you can get a problem during the meiosis, one egg or sperm cell ending up with two chromosome 21 and the other with none. None is lethal, three of them means a genetical problem called "Mongolismus" or Trisomie 21 in German. English word is similar, i suppose. But as you can conclude from the above you neednt get a problem during meiosis, if the two glued together chromosomes get in one cell and the two ones not glued to gether in the other.
But imagine an individual would have both its chromosome 21 attached to his chromosome 14, then you have a specimen with one pair of chromosomes less than the others, as this would look like one then (function of the genes is not affected).
If there are several such individuals in a small founder population, you may get a species with one chromosome pair less.

I think, thats it, roughly...

Joern

 

[Charles Harper]

OK, think I got it... generally. I thought all Drosophila had just 4 pairs of chromosomes too, but I'm no geneticist. (Your 'Trisomie 21' is, I presume, our 'Down's syndrome', once called 'mongolism', a rather unfair appelation.)

Thanks, Joern.