O ne of the most interesting of all dune plants, and certainly one of the most bizarre wildflowers in North America is "sand food" (Pholisma sonorae). This amazing parasitic flowering plant grows in the Algodones Dunes of southeastern California and adjacent Arizona, and in the sand dunes of El Gran Desierto in Sonora, Mexico (north of Bahia Adair in the Gulf of California). Within this area, the plants grow on sand dunes produced by wind transport of sand from the beaches of ancient Lake Cahuilla and the Colorado River delta. Another unusual species of sand food (Pholisma culiacana) is endemic to rocky, subtropical thorn scrub 500 miles (800 km) south in Sinaloa, Mexico. The disjunct distribution of these two species may be explained by plate tectonics. Floras west of the San Andreas fault and Gulf rift, in southern California and Baja California, have been displaced northward at least 500 km since the Miocene epoch (about 30 million years ago). Assuming that P. culiacana is more like the tropical progenitor of both species, P. sonorae could have diverged into a more xeric (drought resistant) species west of the San Andreas fault as peninsular California moved northward. Present day populations of P. sonorae east of the fault could have migrated there by shifting sand dunes in the region.