Well put abiather. However since Darwin's time things have not stood still.
I am sure you will be interested in learning about some examples of speciation... you could try here or here or really you could just google it!
Are suggesting speciation cannot happen? Considering the fact that we understand that DNA is not perfectly copied between generations, surely an animal population separated by geography for long periods of time may drift apart and become different species? It would be interesting to see some evidence of a mechanism that would stop this happening, do you have any ideas on this?