The answer is sometimes yes. When we think about exotic plants growing in a native habitat in California we of think of the invasive weedy type plants such as Star Thistle or Broom that push out the native plants.
However in a ScienceDaily story How native plants and exotics coexist a Brown Ph.D. student discovers there are situations where the exotics may help the natives. He describes an example where an exotic plant becomes the favorite food of an insect that was previously was devastating a neighboring native plant. However, the balance is precarious and this is not advocating for more exotics but more about learning plants' relationships with each.