Cushenbury Oxytheca

Oxytheca parishii var. goodmaniana

Description

Oxytheca parishii var. goodmaniana (Cushenbury oxytheca) is a small wiry annual of the buckwheat family that stands 2-12 in (5-30 cm) tall with a basal rosette of leaves 0.4-1.2 in (1-3 cm) long and stems with bracts at the nodes. The flowers consist of six small white to rose or greenish-yellow petals; clusters of three to 12 flowers are subtended by a distinct involucral bract.

O. parishii var. goodmaniana is separated from the other three varieties of O. parishii by the presence of only four to five awns on the bracts, rather than seven or more.

Habitat

All Cushenbury oxytheca populations occur on limestone or a mixed lithology of limestone and dolomite except the population growing only on dolomite at north Holcomb Valley.

Distribution

Cushenbury oxytheca is the most restricted of the carbonate endemic species of the San Bernardino Mountains. Forest Service surveys in 1992 located three additional populations, bringing the total number of known occurrences to seven. One occurrence close to Cushenbury Spring is located near an active limestone mine; two more occurrences are located near the abandoned Green Lead gold mine, one of which is bisected by a road; the fourth occurrence is located near the north side of Holcomb Valley.

The three most recently discovered populations are located along the Helendale Fault in the vicinity of Tip Top Mountain, Mineral Mountain, and Rose Mine. This represents a significant extension of approximately 12 mi (20 km) to the southeast from the previously known range of the plant. Given the availability of potentially suitable habitat between the newly discovered and the previously known populations, other sites supporting this species may be found with additional surveys.

The total known population in 1990 consisted of less than 3,000 individuals; the discovery of three new occurrences two years later doubled the estimated number of Cushenbury oxytheca plants. Since it is an annual species, the number of individuals might be higher in years with winter and spring rainfall and temperatures favorable to seed germination and seedling establishment. The relatively low number of occurrences and individuals also subjects the species to the possibility of stochastic extinction.

Threats

Cushenbury oxytheca is restricted primarily to carbonate and adjacent carbonate/granitic substrates occupied by pinyon-juniper woodland on the northern side of the San Bernardino Mountains. The imminent and primary threat facing this species is the ongoing destruction of the carbonate substrates on which it grows by activities associated with limestone mining, including direct removal of mined materials, disposal of overburden on adjacent unmined habitat, and road construction. Additional threats to its habitat include off-highway vehicle use, urban development near the community of Big Bear, development of a ski run, and energy development projects.

Conservation and Recovery

One population of the Cushenbury oxytheca occurs on land owned by the University of California at the Burns Pinyon Reserve; no activities are planned that would affect that habitat. The other six known critical habitats are on federal land, mostly managed by the Forest Service, and to a lesser degree the Bureau of Land Management. These critical habitats should be protected from mining and other disturbances. This could be done by appropriate modifications of the management plan for the San Bernardino National Forest. The populations of the Cushenbury oxytheca should be monitored, and research undertaken into its biology and habitat requirements.

Contacts

U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 24 August 1994. "Endangered and Threatened Wildlife and Plants; Five Plants From the San Bernardino Mountains in Southern California Determined to be Threatened or Endangered." Federal Register 59.