Brodiaea santarosae
The Santa Rosa Basalt Brodiaea

Tom Chester, Wayne Armstrong and Kay Madore

Table of Contents

Press Release 13 November 2007
Abstract of Published Paper
Key To The Species Of Brodiaea In Southern California
Distinguishing Characteristics, including Principal Components Analysis
Geographic Distribution and Basalt Endemism
Madroño Paper (4 MB PDF file)
Additions And Corrections To Madroño Paper


Brodiaea santarosae is a newly-recognized species found only on basalt soils in areas currently or recently covered by the Santa Rosa Basalt of southwest Riverside County and a neighboring small part of San Diego County. It is the rarest of the southern California Brodiaeas, with just four known populations occupying only a small portion of an area only 10 miles long and 3 miles wide, plus a fifth very small population separated by 7 miles from the rest of the population.

Specimens of B. santarosae have previously been confused with two other rare species, B. filifolia and B. orcuttii based solely on two internal parts of its flowers. Our studies have shown these specimens are very different from those other two species; we have found 11 total differentiating characteristics.

Other specimens of B. santarosae have been thought to be hybrids between B. filifolia and B. orcuttii. That hypothesis is ruled out because B. filifolia and B. orcuttii only occur together well to the south of the Santa Rosa Basalt in San Marcos in San Diego County. In fact, we were lucky enough to find true hybrids of B. filifolia and B. orcuttii in San Marcos. Those hybrids are clearly distinguished from specimens of B. santarosae.

Species found only on a given soil type are of great interest to botanists in how they have adapted to difficult soils such as basalt. In fact, a new book just came out in 2006 devoted to such species (Kruckeberg, A. R. 2006, Introduction to California soils and plants, University of California Press). Kruckeberg made a prediction in that book which was borne out by our recognition of this species: most new species will be in places .. with kooky such remote places out of the way places in southern California.

The association with the 8 to 11 million year old Santa Rosa Basalt makes B. santarosae a fascinating species for further study. Some of the interesting possibilities are:

The name was published in mid-October 2007 in Madroño 54:187-198.

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Copyright © 2006-2007 by Tom Chester, Wayne Armstrong and Kay Madore.
Comments and feedback: Tom Chester
Last update: 30 November 2007