Big-leaved Crown-beard

Verbesina dissita

Description

Big-leaved crown-beard, Verbesina dissita, is a low, semi-woody perennial shrub with bright yellow flowers that belongs to the aster family (Asteraceae or Compositae). This species reaches a height of 1.6-3.3 ft (0.5-1 m) and has distinctive scabrid leaves.

V. dissita is distinguished from other members of the genus in California and Mexican Baja California by its naked achenes and broad involucre.

V. dissita was first described by Asa Gray in 1885 from a collection made the previous September by Charles Orcutt at Ensenada, Baja California, Mexico. The species apparently was first collected in the United States in 1903 by Mrs. M. F. Bradshaw at Arch Beach in South Laguna, Orange County, California.

Habitat

Big-leaved crown-beard is frequently associated with southern maritime chaparral, although it also extends into other plant communities. This plant is restricted to rugged coastal hillsides and canyons in association with San Onofre breccia-derived soils in the southern maritime chaparral of southern Orange County. Big-leaved crown-beard also occurs in limited numbers in Venturan-Diegan transitional coastal sage scrub, Diegan coastal sage scrub, and southern mixed chaparral. The species also occurs disjunctly in similar vegetation associations from Punta Descanso south to San Telmo in northwestern Baja California, Mexico.

Distribution

Big-leaved crown-beard occurs in two disjunct populations, one in coastal southern Orange County and one along the Mexican coast of northwestern Baja California. The species is found on rugged hillsides in dense maritime chaparral from Laguna Beach in Orange County south to the San Telmo area east of Cabo Colonet in Baja California. The two California occurrences of this plant are located less than two miles apart. The total big-leaved crown-beard population has been difficult to estimate because of its preference for semi-obscured under-story locations and the low-growing posture of individual plants. The United States populations have been estimated to contain several thousand plants, but 85% of the known big-leaved crown-beard locations occur in northwestern Baja California. This species was recorded historically from 23 separate locations in Mexico; more than 20% of these sites (all north of Punta Santo Tomas) have been eliminated. Nearly all known populations are on private land.

Threats

The United States populations of big-leaved crown-beard that occur on private land along a two mile stretch of coastline near Laguna Beach are threatened by residential development and fuel modification activities. This area comprises a still relatively contiguous habitat, but several developments have been proposed that will reduce and substantially fragment this rare vegetation association. In Orange County, big-leaved crown-beard extends into Aliso/Woods Canyons Wilderness Park; however, this park encompasses only about 20% of the habitat suitable for this species and less than 10% of the known individuals. Although this county regional park is partly managed for biological conservation, big-leaved crown-beard is nevertheless threatened here by the fuel modification techniques of mechanical clearing, thinning, and irrigation. Exotic vegetation invading from the park boundary is also a considerable threat.

Residential development and fuel modification activities continue to do incremental harm to the main Laguna Beach population. At least four residences were built directly on big-leaved crown-beard plants after its state-listing as a threatened species in 1989. Although the individual houses eliminated a relatively small number of plants, local ordinances require the creation of a fuel modification zone up to 150 ft (45 m) from the residence. Over 20% of V. dissita occurrences are within 150 ft of residential development. A significant portion of this species in the United States would be eliminated if these ordinances are fully implemented. A fuel break was cut through one population on Temple Hill in 1984. The species normally persists in relatively dense brush, although it is known to respond favorably to some clearing and fires. The plants in the fuel break began to decline after four years. In 1991, the City of Laguna Beach used goats to clear fuel breaks despite objections that the goats could potentially consume rare plant species. The City of Laguna Beach has indicated that many areas containing dense brush adjacent to residential development will be cleared, areas occupied in part by big-leaved crown-beard. One development completed in 1989 has placed irrigation and hydro-mulching over one population of this plant. Big-leaved crown-beard is not expected to persist with overwatering and competition from Atriplex semi-baccata (Australian saltbush), a plant frequently used in landscaping along the borders of development.

The majority of big-leaved crown-beard populations are south of the United States-Mexico border in a coastal area of northwestern Baja California, where it occurs in vegetation associations similar to those found in Laguna Beach. The status of this plant and its habitat in Mexico are not well documented, although one prominent researcher has found the distribution of this species to be spotty in Mexico. Over 20 populations are known between Punta Descanseo and San Telmo near Cabo Colonet. A survey of historic localities in 1988 between Punta el Descanseo and Punta Santo Tomas determined that over 25% of these localities had been urbanized or converted to agriculture. Four separate localities are known from Punta Bunda just south of Ensenada, but three of these are threatened by changes in land use that occurred between 1987 and 1990. These lands went from a relatively pristine state to being extensively cleared for rural condominium development. The same factors of urban and agricultural development that threaten the species in the United States also threaten it in Mexico. Agricultural conversion, slash and burn practices, resort and residential development, and wide fuel breaks have already affected and continue to contribute to the decline of this listed species in Mexico.

Although big-leaved crown-beard is extremely threatened in the United States by development and fuel modification activities, the status of this plant in Mexico is considerably better due to a larger number of extant populations. The collective condition of the two national populations has led the Fish Wildlife Service to list this species as threatened rather than endangered.

Conservation and Recovery

The big-leaved crown-beard is only known from two privately owned sites in California, and from a disjunct area of 23 sites in Baja California. Conservation of this species in California requires that its habitat be protected. This could be done by acquiring the sites and establishing an ecological reserve, or by negotiating conservation easements with the landowners. In addition, the habitat must be protected from damaging practices, such as the construction of fire breaks and prescribed burns to reduce fuel loading. The habitat in Baja California is not protected from agricultural conversion, resort and residential development, or fuel-load management. The most important critical habitats of the big-leaved crown-beard in Mexico should be identified and conserved using methods noted above. The populations of the rare plant should be monitored, and research undertaken into its biology and ecological requirements, with a view to developing methods of managing its habitat.

Contacts

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
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Carlsbad Field Office
2730 Loker Avenue West
Carlsbad, California. 92008-6603
Telephone: (760) 431-9440
Fax: (760) 431-9624

Reference

U. S. Fish and Wildlife Service. 7 October 1996. "Endangered and Threatened Wildlife and Plants: Determination of Endangered or Threatened Status for Four Southern Maritime Chaparral Plant Taxa from Coastal Southern California and Northwestern Baja California, Mexico." Federal Register 61 (195): 52370-52384.