[Ichneumon]

Continue this trend for hundreds of thousands or millions of years and the descendants of chihuahuas and Great Danes will most certainly be considered separate species of animal.

I don't think anyone can dispute that if we had first run across the Chihuahua and the Great Dane out in the wild, with no other varieties of dog extant (if they had died out, for example), we would not have hesitated in the least to consider them separate species.

They're certainly more different morphologically, and more reproductively isolated, than many other creatures which people comfortably label as different species (such as distinct varieties of birds, etc.)

[HankReardon]

This is a real hoot! I can't believe y'all spent all day on this.