That’s not the definition of a species. In fact, that’s a long term effect of sp

That’s not the definition of a species. In fact, that’s a long term effect of speciation. Speciation requires only a differentiation that influences selection. For example, frogs in chernobyl turning from green to black (darkbrown) by melatonin mutation. Or the famous british white moths that turned black because of the spread of a rare mutation as soot accumulated on birch trees. Or as we watch generations of bacteria adapt to survival in a medium with an antibiotic. It’s visible over just a few days.