New dolphin from Australia

In another example of how what scientists find is often quite different from what they look for, Dr. Luciana Möller of Australia's Macquarie was trying to unravel the relationships of bottlenose dolphins (Tursiops truncatus) from Australian coastal waters. The DNA, though, diverged more than she expected: so much that dolphins from southern Australia should should be considered a new species, even if they look very much like their cousins around Australia and around the world (the bottlenose dolphin gets around).
COMMENT: This is important stuff, but it raises anew the question of what degree of difference, and/or what specific differences, are adequate to prove that populations are separate (non-breeding) species. I asked two scientists of my acquaintance that question, and both Ph.D.'s threw up their hands.