|Listed||July 19, 1990|
|Description||Branching annual, bearing white flowers with purple to green tips.|
|Habitat||Valley saltbush scrub and juniper woodland.|
|Threats||Conversion of habitat to cropland, urbanization, livestock grazing.|
California jewelflower, Caulanthus californicus, has hairless, usually branching stems, which can range from less than 4 in (10 cm) to more than 20 in (50 cm) tall. The upper leaves are egg-shaped and clasp the stem, unlike the leaves at the base of the plant, which are oblong. The maroon buds are clustered at the tip of the stem and contrast with the translucent, white flowers below. The fruits of California jewelflower are 0.4-2.4 in (1-6 cm) long, and flattened.
California jewelflower differs from all other species of Caulanthus in that it has flattened, sword-shaped fruits and spherical seeds. Other jewelflowers also have maroon buds and whitish flowers, but those that overlap in range with California jewelflower have narrow, elongated fruits and flattened seeds.
California jewelflower is an annual, and the entire life cycle from seed germination to seed set is completed in a single growing season. As is typical of annuals, both plant size and population size in California jewelflower can vary dramatically, depending on site and weather conditions.
Seeds of California jewelflower begin to germinate in the fall when the rainy season begins, but additional seedlings may continue to emerge for several months. California jewelflower seedlings develop into rosettes (clusters of leaves at ground level) during the winter months, and the stem elongates as flower buds begin to appear in February or March. Flowering and seed set continue until the plants die, which may occur as late as May in years of favorable rainfall and temperatures. Seed-dispersal agents are not known, but may include gravity, seed-eating animals, wind, and water.
California jewelflower probably forms a persistent seed bank. In greenhouse trials, viable seeds did not germinate even when exposed to a variety of typical temperature and moisture conditions. Only conditions simulating prolonged weathering induced seed germination. A persistent seed bank ensures that some seeds will be available to produce plants in succeeding years, even if no individuals survive to set seed in one unfavorable growing season. The presence of a seed bank would explain the reappearance of California jewelflower in uncultivated areas where it had not been observed for decades.
In 1992 and 1993, which were years of above-average rainfall during the growing season, 46-85% of plants in study areas on the Carrizo Plain survived long enough to produce seed. In years of below-average precipitation or above-average temperatures, however, all the plants died before setting seed. Seed production in California jewelflower may vary greatly among individuals, sites, and years.
California jewelflower occurs in non-native grassland, Upper Sonoran Subshrub Scrub, and Cismontane Juniper Woodland and Scrub. Historical records suggest that California jewelflower also occurred in the Valley Saltbush Scrub community in the past.
Herbaceous cover was dense at most California jewelflower sites studied in 1993. Native plant species, such as annual fescue, clovers, red maids, and goldfields comprised a high proportion of the vegetation at many of the known locations over several years. The exotic grass red brome was a significant component of the vegetation only at the Carrizo Plain sites. On the Carrizo Plain, California jewelflower occurred primarily on the burrow systems of giant kangaroo rats, another endangered species.
Populations of California jewelflower have been reported from approximate elevations of 240-2,950 ft (70-900 m) and from level terrain to 25% slopes. Soils at known sites are primarily subalkaline, sandy loams.
The historical distribution of California jewel flower is known from 40 herbarium specimens, which were collected in seven counties between 1880 and 1973. Approximately half of the collection sites were on the floor of the San Joaquin Valley in Fresno, Kern, and Tulare Counties. Several other collections came from two smaller valleys southwest of the San Joaquin Valley, the Carrizo Plain and the Cuyama Valley. Three occurrences were in the Sierra Nevada foothills at the eastern margin of the San Joaquin Valley in Kern County. The remainder of the historical sites were in foothills west of the San Joaquin Valley, in Fresno, Kern, and Kings Counties.
By 1986, all the occurrences on the San Joaquin and Cuyama Valley floors had been eliminated, and the only natural population known to survive was in Santa Barbara Canyon, which is adjacent to the Cuyama Valley in Santa Barbara County. A small, introduced colony also existed at the Paine Preserve in Kern County at that time. Since then, several more introductions have been attempted, and a number of colonies were rediscovered in two other areas where the species had been collected historically. The naturally occurring populations of California jewelflower that were known to be extant in the late 1990s were in three centers of concentration: Santa Barbara Canyon, the Carrizo Plain in San Luis Obispo County, and the Kreyenhagen Hills in Fresno County. Additional populations of California jewelflower may occur in the foothills of Fresno, Kern, and Kings Counties, where potential habitat remains in rangeland. Access to historical sites in these areas has been restricted, however, so the presence of the species has not been verified in more than 50 years.
The primary reason for the decline of California jewelflower was habitat destruction. All the populations on the San Joaquin and Cuyama Valley floors have been eliminated. Conversion to agriculture accounted for the loss of most sites, but those closest to Bakersfield and Fresno were destroyed by urbanization. Oilfield activity may have eliminated a few sites in the foothills at the western margin of the San Joaquin Valley.
Development remains a threat in Santa Barbara Canyon, where more than 90% of the California jewelflower metapopulation occurs on private land. The California jewelflower habitat near the canyon mouth is for sale; the landowner cleared California junipers from the site and planted ornamentals in anticipation of resident development. On private land in the upper portion of Santa Barbara Canyon, California jewelflower is subject to cattle grazing through the growing season, but the magnitude of the threat posed by livestock is unknown. Grazing in the period between rosette stage and seed set is believed to be detrimental to California jewelflower because seed set would be reduced if flowering or fruiting stems were consumed.
Red brome could be particularly competitive because some strains are resistant to air pollution. Insecticides could present a threat to California jewelflower viability on the Carrizo Plain by decreasing pollinator populations. Prior to 1980, the California Department of Food and Agriculture sprayed malathion on the Carrizo Plain to control beet leafhoppers. The effect of malathion on native insect populations has not been investigated. Thus, it is unknown whether fall spraying would affect pollinator populations the following spring, or how large a buffer zone would be needed to avoid affecting insects that pollinate California jewel-flower. Under the current environmental assessment and pesticide use permit, spraying has been suspended on the Carrizo Plain, at least through 2001. Small population size may be another factor in the continued existence of California jewel-flower.
Conservation and Recovery
The known California jewelflower habitat in two of the three concentration areas is in public ownership. The Carrizo Plain metapopulation is entirely within the Carrizo Plain Natural Area, which is administered jointly by the U. S. Bureau of Land Management (BLM), the Nature Conservancy, and the California Department of Fish and Game. The BLM also administers and has monitored since 1991 the Kreyenhagen Hills and a small part of Santa Barbara Canyon. The BLM no longer allows green-season grazing in California jewelflower habitats under its management, which include approximately 40% of individuals known to exist. In 1994, an exclosure was constructed around the plants on public land in Santa Barbara Canyon to preclude grazing.
Several experimental introductions of California jewelflower have been attempted in Kern, Santa Barbara, and Tulare Counties on lands protected by the Nature Conservancy and the Los Padres National Forest. In all instances, the number of plants at each site has declined precipitously following the initial seeding. Possible causes of failure included unfavorable site conditions, use of seed sources that were not adapted to the introduction site, lack of genetic diversity in the introduced populations, and insufficient numbers of seeds. Considering the variable germination rates in natural populations, plants may reappear at some of the reintroduction sites after several years.
Although restoration of California jewelflower to all its former sites of occurrence is not feasible, the recovery goal is to maintain self-sustaining populations in protected areas representative of the former geographic and topographic range of the species and in a variety of appropriate natural communities. Surveys will be necessary to determine whether natural populations remain in all target areas. Where natural populations no longer exist, such as the floor of the San Joaquin Valley, reintroduction will be necessary to achieve recovery.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619
Heady, H. F. 1977. "Valley Grassland." In Terrestrial Vegetation of California, edited by M. G. Barbour and J. Major. Wiley, New York.
Hoover, R. F. 1970. The Vascular Plants of San Luis Obispo County, California. University of California Press, Berkeley.
Taylor, D. W., and W. B. Davilla. 1986. "Status Survey of Three Plants Endemic to the San Joaquin Valley." U. S. Fish and Wildlife Service, Sacramento.