A very interesting point raised in this clip: different breeds could become different species, because they can no longer interbreed.
Size and phenotype (“mechanical reasons”) are not the only thing keeping these different strains from interbreeding.
Cultural reasons play a bigger role. Most purebred dogs exist within a closed registry system or within what amount to Potemkin open registries.
Those have not been around very long, but if they continue for thousands of years, they could result in many speciation events.
Of course, one thing will prevent this happening: inbreeding depressions.
These breeds all have relatively small founder populations, and this problem is further exacerbated by the process of intense line-breeding and the fact that just a few sires in any given breed produce such a large bulk of puppies in any given generation.
Inbreeding depressions almost always mean fertility issues, as we have seen in the wild cheetah population.
That means that if dogs were to ever speciate by breed they would be in as much trouble as cheetahs are today.
Of course, dogs haven’t speciated.
They haven’t even speciated from their wild ancestor, which means we have plenty of opportunities to ensure that the domestic dog population remains viable.
I know this sounds a bit alamist, and in terms of genetic variance, domestic dogs are a long way from becoming many different species.
However, if we continue down this path, we are headed toward crisis.
It is more likely that genetic diversity issues will put a halt to any speciation.
But in theory, they could all become separate species.
In theory.
