Plants of the SRPER: Ranunculus occidentalis: Speculation About Its Former Misdetermination

See Plants of the SRPER: Ranunculus occidentalis for the introduction to this page.

The probable source behind the classification of all southern California plants as "R. californicus", including the SRP plants, is a 1948 monograph by Lyman Benson, an eminent botanist of southern California plants. This is still by far the most thorough and best documented study of the problem and followed by most North American workers (quotes from the 1997 Flora of North America treatment).

Benson published an absolutely beautiful map, which very cleanly separated all the Ranunculus taxa geographically (see his book Plant Taxonomy, p. 294). In southern California, he shows only R. californicus, with var. californicus confined to the very immediate coast south of the Los Angeles basin, and var. austromontanus very local in the southern California mountains. The closest R. occidentalis is in the southernmost Sierra Nevada, some 150 miles away from the Santa Rosa Plateau.

This beautiful map, which shows no disjuncts at all for any of the 21 plotted taxa, is probably the source of the desire to call all southern California plants "R. californicus". Due to the difficulties in some species determinations, botanists are often prone to following such distribution maps by authorities with question.

However, Benson never saw a plant from the SRP; he indicates no population of Ranunculus near there at all. I strongly suspect that if Benson was asked to determine the plants at the SRP, he would have no hesitation in calling them R. occidentalis.

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Copyright © 2006 by Tom Chester
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Last update: 16 December 2006