Layne's Butterweed

Senecio layneae

Description

Senecio layneae (Layne's butterweed) is a perennial herb of the aster family (Asteraceae or Compositae) that sprouts from a rootstock. Its mostly basal lance-shaped leaves are 3-10 in (8-24 cm) long. The several flower heads are 2-3 in (5-8 cm) wide, each having five to eight orange-yellow ray flowers and numerous yellow disk flowers. Layne's butter-weed flowers between April and June. Kate Bran-degee Layne-Curran collected the type specimen for Senecio layneae in May 1883 from El Dorado County, California, on Sweetwater Creek, not far from Folsom. E. L. Greene first described Senecio layneae in 1883. Although Asa Gray reduced Senecio layneae to a variety of Senecio fastigiatus the following year, the species currently is known as Senecio layneae. The type population is now thought to be extirpated due to inundation by Folsom Lake.

Habitat

Layne's butterweed grows in open rocky areas within chaparral plant communities, primarily on gabbro-derived soil formations and occasionally on serpentine soils. Layne's butterweed mostly occurs in fire-dependent chaparral habitat, but it also appears in the ecotone between chaparral and oak woodland. This taxon also can occur directly in oak woodland.

Distribution

Most known sites are scattered within a 40,000 acres (16,000 hectares) area in western El Dorado County that includes the Pine Hill intrusion and adjacent serpentine. A few other colonies occur in the Eldorado National Forest in El Dorado County and in the Bureau of Land Management (BLM) Red Hills Management Area in Tuolumne County. Layne's butterweed primarily occurs on privately owned land. Some populations of Layne's butterweed also occur on federal land managed either by the Forest Service or BLM. One site is on land managed by California Department of Forestry (CDF) and California Department of Fish and Game (CDFG).

Threats

Residential and commercial development, road maintenance, change in fire frequency, off-road vehicle use, competition with invasive alien vegetation, excessive horse grazing practices, mining, and other human-caused conditions threaten and are responsible for the declining trend for Layne's butterweed.

Commercial and residential development extirpated two occurrences of Layne's butterweed. Many of the remaining occurrences of Layne's butterweed are in areas undergoing rapid commercial and residential development. Layne's butterweed is also potentially threatened by a variety of disturbances including road maintenance, vegetation removal, and off-road vehicle use. Road widening occurs in the vicinity of development within El Dorado County, and this activity has already extirpated one occurrence and threatens an additional five sites there. Intensive off-road vehicle use threatens two additional occurrences of this species. Off-road vehicle use occurred historically in Tuolumne County on BLM land, but this activity no longer occurs there. Currently, off-road vehicle use occurs on two sites within the Pine Hill intrusion on privately owned land. One site of this plant in the northern part of the intrusion, already fragmented by the numerous roads that traverse the entire area, is further damaged by heavy off-road vehicle use. A southern site of Layne's butterweed that occurs across 221 acres (89 hectares) was cleared in preparation for development and is subject to off-road vehicle use over part of the site.

The suppression of fire and other forms of disturbance threatens Layne's butterweed. Limited surface disturbance is beneficial to this species in certain circumstances by promoting initial establishment. Layne's butterweed appears to be an early successional species that occupies temporary openings on gabbro-derived or serpentine soils and is eliminated as vegetation regrows in the openings.

Competition with invasive alien vegetation and shading from native tree and shrub species potentially threaten Layne's butterweed. Several alien plant species, including Cytisus scoparius (Scotch broom), have become established within the Traverse Creek Botanical Area in Eldorado National Forest and potentially threaten this occurrence of Layne's butterweed.

One occurrence of this taxon is thought to have been extirpated by roadside herbicide application. This activity may threaten several other occurrences of this species.

Overgrazing by horses in rural residential areas within the Pine Hill intrusion threatens Layne's butterweed. The horses, when confined, severely graze virtually all available vegetation.

Habitat for this taxon within the Traverse Creek Botanical Area in Eldorado National Forest historically was fragmented by serpentine quarrying. Mining claims for semi-precious stones and gold also exist on Layne's butterweed habitat in the Eldorado National Forest. Although the Eldorado National Forest is trying to withdraw these claims, the withdrawal action may not be achieved.

Conservation and Recovery

The Layne's butterweed occurs on federal land in the Eldorado National Forest (Forest Service) and the BLM Red Hills Management Area, and on state land managed by the CDF and the CDFG. The critical habitat in these areas should be protected against threatening activities. This can be achieved by suitable modifications of the management plans for these areas. However, most of the critical habitat of the Layne's butterweed is on privately owned land, and is threatened by development and incompatible landuse. These critical habitats should be protected. This could be done by acquiring the private land and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Layne's butterweed should be monitored, and research undertaken into its biology and habitat needs, including methods of beneficial management.

Contacts

U.S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
Federal Building
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

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/

Reference

U.S. Fish and Wildlife Service. 18 October 1996. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Four Plants and Threatened Status for One Plant from the Central Sierran Foothills of California." Federal Register 61 (203): 54346-54358.