You discount the African and Indian elephant example because they are both elephants. However, you fail to mention there are far more physical differences between the two than simply the size of their ears.
You fall for the ignorant view that they are the same species.
In fact, even the African Savanna elephant and the African forest elephant are considered to be different species. Probably not by your simplistic definition tho....
http://www.nature.com/news/2010/101221/full/news.2010.691.html
See, there is this stuff called DNA which kind of exposes arguments like yours.
The awful thing for you to contemplate is that DNA shows us, in fact proves to us, that your argument of species variation applies to every living thing on the planet. There is only a 1% difference between your DNA and a chimp's.
The genetic difference between African and Indian elephants is larger than that. If you're going to say African and Indian elephants are one species, you have to agree humans and chimps are one species, surely?
http://news.sciencemag.org/plants-animals/2012/06/bonobos-join-chimps-closest-human-relatives
Now ask yourself why are these three species of elephants physically different? And how much greater will the differences be in another few million years?
