Stebbins' Morning-glory

Calystegia stebbinsii

Description

Calystegia stebbinsii (Stebbins' morning-glory) is a leafy perennial herb in the morning-glory family (Convolvulaceae). Its stems range up to 3.28 ft (1 m) in length and generally lie flat on the ground. The leaves are palmately lobed with the two outermost lobes being divided again. The leaf lobes are narrow and lance-shaped. White flowers, which appear in May through June, are on stalks 1-5 in long and bear two leaf-like bracts. The fruit is a slender capsule. Its distinctively shaped leaves, each having seven to nine narrow lance-shaped lobes, distinguish C. stebbinsii from other California morning-glories.

G. Ledyard Stebbins collected the type specimen of C. stebbinsii in 1970, 10 mi (16 km) west of Placerville in El Dorado County, California. Richard K. Brummitt described the species in 1974 using specimens collected by Stebbins as the type.

Habitat

Stebbins' morning-glory is associated with chap-arral on gabbro-derived soils in El Dorado county; in Nevada County it occurs on serpentine. Stebbins' morning-glory occurs in fire-dependent chaparral habitat.

Distribution

Stebbins' morning-glory occurs in two localized areas. Most occurrences are discontinuously scattered within two population centers in the northern and southern portions of the Pine Hill intrusion. Stebbins' morning-glory does not occur at the center of the intrusion on Pine Hill. It recently was discovered in Nevada County near the County landfill, where it was sparsely scattered over a distance of 3.5 mi (5.6 km). The species may have been transplanted from El Dorado County by the transport of soil to the Nevada County Sanitary Land-fill. Stebbins' morning-glory occurs primarily on privately owned land, although the Bureau of Land Management (BLM) manages land harboring some occurrences.

Threats

Development has extirpated at least one-third of the known occurrences. Other threats to these populations include off-road vehicle use, grading, dumping, road maintenance, change in fire frequency, and competition with invasive alien vegetation.

Commercial and residential development has extirpated at least one-third of the known occurrences of Stebbins' morning-glory. Most of the remaining occurrences for Stebbins' morning-glory are on the Pine Hill intrusion. All of these sites, except for those in the northern part, are in areas threatened by rapid residential and commercial development as discussed above. Habitat for Stebbins' morning-glory in Nevada County is threatened by a proposed County works project.

Other human activities also destroy or damage habitat of Stebbins' morning-glory. One occurrence was adversely impacted by grading for construction. Off-road vehicle use has adversely impacted the habitat of Stebbins' morning-glory at one site. In the northern part of the Pine Hill intrusion, several hills are scarred with off-road vehicle tracks. Erosion promoted by scarring adversely modifies the habitat. Road maintenance and herbicide spraying potentially threaten another site of Stebbins' morning-glory that occurs along a road cut.

The suppression of fire and other forms of disturbance threatens Stebbins' morning-glory. Limited surface disturbance is beneficial to this species in certain circumstances because it promotes initial establishment. Studies indicate that seeds of this taxon need disturbance by either heat or scarification for germination. At the Nevada County landfill site, this species is more prevalent in the burned areas than in the unburned sections. Stebbins' morning-glory is eliminated as soon as the surrounding chaparral grows tall enough to shade it.

Competition with invasive alien vegetation, herbicide spraying, and unauthorized dumping threaten individual occurrences of Stebbins' morning-glory. Convolvulus sp., an introduced species of field bindweed, competes with one colony of Stebbins' morning-glory within Nevada County. Trash dumping also threatens three occurrences of this taxon. Herbicide spraying potentially threatens a significant portion of one occurrence of this plant near Shingle Springs and several local occurrences adjacent to roads.

Overgrazing by horses in rural residential areas within the Pine Hill intrusion threatens Stebbins' morning-glory. The horses, when confined, severely graze virtually all available vegetation.

Conservation and Recovery

The Stebbins' morning-glory only occurs in scattered locations within two population centers. Some of its critical habitats are on federal land managed by the BLM. This publicly owned habitat should be strictly protected from any threatening activities. Other habitat is on privately owned land. These critical habitats should also be protected. This could be done by acquiring the habitats and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Stebbins' morning-glory should be monitored, and studies made of its habitat needs.

Contacts

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

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. 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.