Harmonia stebbinsii

This representative of the tarweed group is an endangered endemic to California, and characteristically associated with shallow, rocky, serpentine soils. It is only found in the narrow geographical range of Lake, Shasta, Tehama, and Trinity counties of California’ Klamath Mountain Ecoregion. Occurrences outside of this range have not been documented. Ecology. Ultramafic, “serpentine” soils in California support a high rate of endemism in plant communities. Plate tectonics and erosion over time work to produce these unique soil environments that are characterized by high levels of magnesium and iron silicate materials. In addition, they feature low levels of important plant nutrients, including nitrogen, phosphorus, potassium, and calcium. In addition, these soils contain trace minerals that are toxic to most plants, including cobalt, chromium, and nickel. California contains approximately 2300 square miles of ultramafic rocks. Thus, plants found in these environments have the adaptive ability to grow, despite these conditions. Furthermore, such an extreme environment facilitates the high rate of endemism found, as few species are able to dominate a serpentine plant community. Of all of the endemic California plants, those of the family Asteraceae have the highest affinity for serpentine soils, based on the number of species represented in these serpentine plant communities. Most serpentine endemism is concentrated in the North Coastal and Klamath Mountain Ranges of northwestern California and southwestern Oregon.