Brodiaea santarosae (Themidaceae) is a new species from southwest Riverside County and immediately-adjacent Miller Mountain of San Diego County, CA. It is easily distinguished from other Brodiaea species in southern California by its large flowers and distinctive, variable staminodes; morphological analysis revealed 11 total differentiating characteristics. Brodiaea santarosae occurs only on or very close to the 8–11 million-year-old Santa Rosa Basalt. It has the smallest range of the southern California Brodiaeas, with just four known populations occupying only a small portion of a ∼40 km2 area, plus a fifth small population disjunct by 11 km.
It has been speculated that the B. santarosae population is a hybrid swarm between B. filifolia and B. orcuttii, based solely on the appearance of the staminodes and filaments in selected flowers. This speculation was rejected due to the lack of sympatry between the three taxa and because specimens of B. santarosae have numerous characteristics that are not intermediate between the claimed parent taxa. In contrast, intermediate characteristics were seen in F1 specimens of B. filifolia X B. orcuttii discovered in San Marcos, CA, the only location where those species overlap.
We also report extensions to the length characteristics for both B. filifolia and B. orcuttii and demonstrate that two populations of B. filifolia previously thought to be hybrids are consistent with other B. filifolia populations.