[Karen]

Karen asked the Naked Scientists:

Hi, I have recently built a small aviary in my back yard. It has predominantly zebra finches, which got me to wondering...

If all dog breeds are able to interbreed eg. dalmation with silky (albeit with difficulty) and are able to produce offspring, would a zebra finch breed with a different type of finch? eg. zebra finch with gouldian?

The birds seem less different to each other than the dalmation and silky would?


What do you think?

[SquarishTriangle]

I think the definition of a species is that its members can produce viable, fertile offspring. So in theory, the possibililty of them reproducing successfully would be unlikely, although certain combinations of 2 species have been known to produce hybrid, non-fertile (ie. dead-end) offspring (eg. mules).

In the case of domestic dogs, they are all breeds of the same species and can therefore breed to produce viable offspring. I think the situation is that despite distinct characteristics having arisen between breeds by extensive artificial selection, chromosomal number and sufficient genetic similarity are conserved within members of the species. That allows cross-breeding to occur successfully, provided any physical difficulties can be overcome!

[blakestyger]

That's right, dogs are all the same species but different varieties brought about by selective breeding.
Birds in the wild will hybridise viably between species but usually within the same genus; examples are tufted duck/pochard and scaup/pochard. Having said that I've seen hybrids between different genus geese: Canada/greylag.
Bird hybrids usually occur when speciation has been caused by geographical separation of populations
along clines. It is unlikely you would ever get a woodpecker X crow, for instance as the common ancestor for theses two would have been just too far back.