Plants of Southern California: Stephanomeria Geographic Distribution
The following maps show the locations of all the Stephanomeria individuals that have a positively-identified species determination through detailed examination of their fruit. In order to see the locations more clearly, I have plotted different areas of Southern California separately.
Northwest San Diego County Area
All the data points were collected by myself, except for two S. diegensis points that straddle I-15 near the middle of the plot; one from James Dillane for Daley Ranch, and one from Wayne Armstrong for the Merriam Mountains in the middle of the plot. The lowest latitude points are Torrey Pines State Reserve on the west and Blue Sky Ecological Reserve / Mt. Woodson on the east.
The boundary between S. virgata and S. diegensis occurs at about 20 miles inland from the coast in San Diego County. Unfortunately, the data points needed to determine the precise boundary are mostly in areas burned in 2003, so a definitive map may have to wait until next year.
The other interesting thing about the map is the apparently-restricted distribution of S. exigua. It is essentially the only species found immediately next to the Santa Margarita River. Many hundred specimens of S. exigua ssp. deanei are found there, with only a single specimen of S. diegensis found close to the river. No specimens of S. exigua were found at Torrey Pines State Reserve and Blue Sky Ecological Reserve / Mt. Woodson. However, S. exigua might be present in the Merriam Mountains and at Daley Ranch, since James and Wayne only sample the S. virgata / S. diegensis population there.
Entire San Diego County Area
Note that the symbols used in this plot are not the same as the ones in the previous plot.
The above plot shows the confirmed vouchers from the San Diego County Plant Atlas as of 8 February 2006. Surprisingly, vouchers for S. diegensis extend a full 45 miles from the coast, all the way to the boundary with Anza-Borrego Desert State Park!
At least in San Diego County, it thus appears that S. diegensis is the more common, more widespread taxon, with S. virgata uncommon and confined to a significantly smaller area.
Santa Monica Mountains and San Gabriel Mountains Region
The map for the Santa Monica Mountains and San Gabriel Mountains Region will be supplied later.
For more information about these specimens, see the following links for each species.