[Wikipedia] Range, Genetic Variability, Hybridization: It is native to six islands: five of the Channel Islands of California (Anacapa Island, San Clemente Island, Santa Catalina Island, Santa Cruz Island, and Santa Rosa Island) and Guadalupe Island, part of the State of Baja California.[7] This species is a relict. Though it is now limited to the islands, it was once widespread in mainland California, as evidenced by the many late Tertiary fossils of the species found there.[5] Recently, it was found that there was a high genetic variability across many of the Q. tomentella populations, but this variation was not evenly distributed. Island oak hybridizes with canyon live oak (Quercus chrysolepis). (link added by Mary Ann Machi)