|Listed||May 29, 1984|
|Description||Evergreen shrub with prominently veined leaves and white or yellow flowers.|
|Habitat||Gravelly clay-loam soils over limestone.|
|Threats||Livestock grazing, mining, low reproduction.|
Arizona cliffrose, Purshia subintegra, is an evergreen shrub with pale gray, ragged bark that grows up to 30 in (75 cm) in height. Leaves, twigs, and flowers are covered with dense, short, white hairs. The leaves have a prominent vein and are untoothed or sometimes lobed. The five-petaled flowers are white or yellow and up to 1.2 in (3 cm) long. The horizontal lower branches are spreading, and the central branches are irregularly ascending. New shoots tend to be rust-colored; the older branches have light gray bark that becomes shredded with age.
Arizona cliffrose grows in gravelly clay loam soils over limestone. It is found on low rolling hills in the Arizona upland area of the Desert Formation. Habitat elevation is between 2,050 and 3,660 ft (625 and 1,115 m). Associated desert scrub plants are dominated by creosote bush, rabbitbrush, false palo verde, and catclaw acacia.
This cliffrose species is closely related to Cowania ericaefolia, which grows in the Chihuahuan Desert of Trans-Pecos Texas and Coahuila, Mexico. The widely separated ranges of these two species suggest a prior continuous range that long ago became fragmented. Botanists consider these and other limestone endemics valuable for understanding the evolution of southwestern floras.
Four disjunct Arizona cliffrose populations are currently known along the northern edge of the Sonoran Desert. They occur along the sub-Mongollon region of central Arizona over a 200 mi (321.9 km) range. The first known population was found along Burro Creek in southeastern Mohave County. In 1968, a second population was discovered near Bylas in Graham County. In 1984 and 1985 two additional populations areas were documented near Cottonwood in Yavapai County and near Horseshoe Lake in Maricopa and Yavapai Counties.
Each population of Arizona cliffrose has unique biological and ecological characteristics and threats. Dangers to the species include livestock and burro grazing, mineral exploration and development, construction and maintenance of roads and utility rights-of-way, recreation, poor reproduction, off-road vehicle use, urbanization, pesticides, and inundation.
At all sites the plant is reproducing at a very low rate. Seeds collected from Burro Creek plants were found to be non-viable. At the Graham County site, researchers found few seedlings and little fruit production. Such reproductive problems make any disturbance to existing plants a particular threat.
Mining exploration at the Burro Creek site, which requires scraping the surface to expose subsurface formations, is another threat, as the technique destroys plants and causes extensive damage to the ecosystem. Browsing by cattle, mule deer, and feral burros also threatens the Arizona cliffrose.
Conservation and Recovery
Since populations occur on lands managed by the Bureau of Land Management (BLM), the Bureau of Indian Affairs, or the state of Arizona, protection of the plant and its habitat is feasible. The BLM has adopted a management plan for the cliffrose that calls for close supervision of mining activities and livestock grazing. In 1989, the BLM constructed a fence that excludes cattle and burros from most of the largest subpopulations.
The Arizona Cliffrose Recovery Plan, released by the U.S. Fish and Wildlife Service in March 1995, outlines a recovery criteria, including the maintenance of the four viable populations, protection of sufficient quantity and quality of habitat needed to support viable populations, regulatory mechanisms or written land management commitments that provide for long-term protection, and determination that the species no longer is endangered. The five basic actions called for in the plan are the production of management plans for the four recovery units; the conduction of research to guide recovery efforts; the elimination or minimization of threats; the enforcement and application of existing laws and regulations; and the development of programs to inform and educate land users. The plan notes that if continuous progress is made, downlisting may be possible by 2008.
Kearney, T. H. 1943. "A New Cliffrose from Arizona." Madroño 7:15-18.
Phillips, A. M., et al. 1980. "Status Report: Cowania subintegra. " Office of Endangered Species, U. S. Fish and Wildlife Service, Albuquerque.
U.S. Fish and Wildlife Service. 1986. "Arizona Cliffrose Recovery Plan, Technical/Agency Review Draft." Endangered Species Office, Albuquerque.
U.S. Fish and Wildlife Service. 1995. "Arizona Cliffrose Recovery Plan." Endangered Species Office, Albuquerque.
Van Devender, T. R. 1980. "Status Report: Cowania subintegra." Arizona Natural Heritage Program, Tucson.