The western scrub-jay is now made up of three species. These would be separated by the Great Basin, with the Pacific coastal lineage (California scrub-jay) and the island scrub-jay, as well as the inland lineage (Woodhouse's scrub-jay), with the Florida scrub-jay being a sister species. This treatment fails to address the problem of birds from inland southern Mexico. Nonetheless, it is actually "because" the molecular diversity pattern is so badly resolved that it supports the view that rapid Late Pliocene radiation of the North American scrub-jays led to the present diversity. Studies on the evolutionary history of "Aphelocoma" jays suggests that all New World jays originated in North America or Mesoamerica.