Can an introduced species ever be considered native?

Debate on the protection of American wild horses

source: Bob Holmes
New Scientist vol 210 no 2817, June 18 2011 p14

Wild horses are found in the western states of the USA. Animal rights groups claim that the horses should not be removed to make space for cattle farming. The federal court case could affect treatment of these horses on federal lands. Horses evolved in North America, but became extinct there aound 10,000 years ago. Wild horses found in the US today descended from European domesticated horses. Modern horses appear to be longer legged and taller than their ancestors, judging by cave paintings. Domestication tends to reduce brain size, though the reduction is smaller in horses, which also develop structured social systems and thrive in a feral state. They may merit protection whether or not they are defined as native.