Santa Ana River
There are two subspecies of this plant. The rarer, ssp. "sanctorum" (Santa Ana River woollystar), is endemic to the Santa Ana River drainage in San Bernardino County, California. It was federally listed as an endangered species in 1987. A resident of higher floodplain habitat types, the plant was expected to suffer from the construction of the Seven Oaks Dam, which would alter the hydrology of the Santa Ana River waterways it depends on.