I would say it has. Evolution is just the change in frequency of alleles within a population. We have seen that many times. If you look at DNA you can get a rough estimate of when two organisms last ancestor was. You can see the beginning of reproductive isolation in species. In plants sometimes diploid turn to tetraploids. They can only produce sterile offspring. One prediction of evolution that holds true is that soldiers should be hard to identify. Since species is a man made term we should expect to see things that are somewhere between species and we do. Look at the Endler livebearer. It is considered a Skechers by some, but can create fertile offspring with the common guppy.