Dodecahema leptoceras

There are thirty five occurrences known with only 19 still extant. The habitat where this species occurs, alluvial terrace, is highly threatened by development, agriculture, off-road vehicle use, non native plants and other threats. The long term trend for this species is one of significant decline due to the alteration and degradation of its habitat, alluvial terrace. Further, short term decline is also quite steep.

This species is known from the foothills of the San Gabriel Mountains in Los Angeles Co., the San Bernardino Mountains of San Bernardino Co., and the San Jacinto Mountains of western Riverside Co. (Flora North America vol. 5).

This species historically extended from the southern base of the Liebre Mountains, Western Transverse Ranges, and the western edge of the San Gabriel Mountains in Los Angeles Co. to the eastern edge of the range at Cajon Canyon in San Bernardino Co. From there it extends southeast from the Santa Ana River wash close to Redlands in San Bernardino Co.. From there it reaches southeast to the San Jacinto Mountains. Finally, it is known from the Temescal Canyon and southeast to Vail Lake/Dripping Springs area (CPC 2007).

A total of 35 occurrences are known, however, only 19 are non-historic.

Habitat replaced by urbanization, agriculture. Urbanization in the Los Angeles area has significantly reduced the number of known norther occurrences (Flora North America vol. 5). Threatened by exotic annuals, sand and gravel mining, grazing, flood control, hydrological alteration, proposed reservoir construction, off road vehicles, and herbivory (CPC 2007).