is their wide morphological diversity not sufficient to classify modern domestic dogs as multiple species (or subspecies) branched from the initial stock?
I would say that with our current usage of 'species', some dog breeds could be considered different species.
Or are there, in fact, larger genetic differences, despite their respective appearances? For example, is there actually a greater genetic difference between, say, a German Shepherd and a Gray Wolf than there is between a German Shepherd and a Pekingese?
I don't know but I would like to know.
Obviously, there is the question of the physical practicality of certain couplings, but is it possible to do, even if only in principle? For instance, could you cross, say, a Great Dane with a Chihuahua via artificial insemination? Would it produce viable offspring? And if you could not, or if the offspring were sterile, would this qualify the two breeds as having become significantly diverged to be classified as separate species?
Aren't there some ring species that
could interbreed, genetically, but don't because of morpholigical differences? If they are considered different species not because they
can't interbreed but because the
don't interbreed, the same could be said of some
species breeds of dogs.
But just to muck up the distinctions some more... A dog and a wolf
can, and will, interbreed to produce viable offspring. I don't think that a great dane and a chihuahua would ever reproduce, naturally.
So where do you draw the line? Do you redefine the word species just because the dogs screwed it up?
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