Manzanitas of San Bruno Mountain County Park – An island of Artctostaphylos endemism
This region is the epicenter for “localized endemism” in manzanitas. Two manzanita species are found on this mountain and nowhere else (A. pacifica and imbricata) and both share space and time with a distinct form of bear-berry (A. uva-ursi), the equally rare Montara Mountain manzanita (A. montaraensis) and the more common brittleleaf manzanita (A. crustacea). The San Francisco Bay area is at the center of the range of biodiversity for the genus Arctostaphylos–which extends from just north of the Oregon-California border southward to northern Baja California, Mexico. Other nearby Bay Area rarities include the Franciscan manzanita (A. franciscana), Presidio manzanita (A. montana ssp. ravenii), and Marin manzanita (A. virgata) to name a few.
In all, more than one-third of all manzanitas in California, or 34 species and subspecies, are found within a short drive of the Bay Area. Of these, 18 are local endemics with six currently occupying ranges of less than one square kilometer! Clearly this endemism offers conservation challenges when a major urban center collides with a hotspot for biodiversity¹. Read more about manzanitas and the diversity in the genus in the new Field Guide to Manzanitas.
Citations:
- Vasey, Michael. 2011. Manzanitas Galore in the San Francisco Bay Area. Friends of the Regional Parks Botanical Garden. Volume 14 #4.