Metcalf Canyon Jewelflower

Streptanthus albidus ssp. albidus

Description

Streptanthus albidus ssp. albidus (Metcalf Canyon jewelflower), is an annual herb of the mustard family (Brassicaceae or Cruciferae) that reaches up to 3 ft (1 m) in height. It has bristly hairs at the base and pale green, strongly glaucous stems and leaves. The flowers are borne in leafless terminal racemes. The upper three of the white to yellow to whitish-green sepals are fused, with the lower sepal free and spreading. The four petals, 0.3-0.4 in (0.8-1 cm) long, are whitish with light purple veins. The erect flattened pods are 1-3 in (2.5-8 cm) long. The only Streptanthus species likely to co-occur with Metcalf Canyon jewelflower is its close relative Streptanthus albidus ssp. peramoenus, most beautiful jewelflower. Streptanthus albidus ssp. peramoenus is distinguished by its lilac-lavender sepals.

Metcalf Canyon jewelflower flowers April to June.

Habitat

Metcalf Canyon jewelflower is endemic to serpentine outcrops with little soil development within a matrix of mostly native serpentine grassland. The species has also been seen on roadcuts through serpentine substrate. It grows between 200-1,200 ft (61-366 m) in elevation. Metcalf Canyon jewelflower grows in areas with other rare species including bay checkerspot butterfly, most beautiful jewelflower, Mt. Hamilton thistle, and Santa Clara Valley dudleya.

Distribution

Metcalf Canyon jewelflower always has been rare. It can be locally abundant, but its range is limited, extending less than 20 mi (32 km) from San Jose south to Anderson Lake, which lies northeast of Morgan Hill in Santa Clara County. Furthermore, the serpentine outcrops on which Metcalf Canyon jewelflower occurs are patchily distributed and comprise only a small percentage of the area within its range.

The 1895 Lower Soda Spring Canyon historic population is the westernmost ever recorded and the 1957 Llagas Avenue population south of Morgan Hill is the southernmost, but both populations may be erroneous. Nine populations have been more recently documented and are known to be extant. Nine populations totaling approximately 20,000-25,000 plants have been recorded.

Threats

The known historical distribution of Metcalf Canyon jewelflower is as restricted as its current distribution. It is found only in the Coyote Valley area of Santa Clara Valley, primarily on the east side of the valley. Metcalf Canyon jewelflower is known to remain at nine of the 14 documented sites; all of the nine are wholly or partially privately-owned. One population is known to have been extirpated by being covered with fill from a housing development, and one was probably extirpated by the construction of Anderson Dam. Three populations known are from historic records. Metcalf Canyon jewelflower was last observed at these historical sites in 1895, 1938 and 1957.

Metcalf Canyon jewelflower is threatened by urbanization. One population consisting of approximately 9,000 plants, approximately 45% of all known plants, occurs on the proposed site of the Cerro Plata residential and golf course project. Although no direct destruction of any plants is planned, construction activities, human disturbance, and habitat fragmentation would result in significant impacts to the population. The original plans to construct Valley Christian School and South Valley Christian Church would have destroyed 1,650 of the 2,700 plants occurring at a second site. However, the revised construction plans avoid impacts to Metcalf Canyon jewelflower.

Cattle grazing has contributed to reduced population sizes of Metcalf Canyon jewelflower and could potentially result in local extinction of the species within its range. Cattle eat or trample individual plants before they mature and set seed. Grazing threatens one population in southeast San Jose and populations in the Metcalf Canyon area.

Metcalf Canyon jewelflower is also threatened by dumping and off-road motorcycle use. Road maintenance or construction threaten populations that occur on roadcuts. One population is adjacent to an active quarry and could be threatened by activities associated with its operations.

Conservation and Recovery

All nine of the surviving critical habitats of the Metcalf Canyon jewelflower are privately-owned, and at great risk of destruction through residential development and other threatening activities. The largest of 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 Metcalf Canyon jewelflower should be monitored, and research undertaken into its biology and habitat needs.

Contacts

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

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. 1998. "Recovery Plan for Serpentine Soil Species of the San Francisco Bay Area. U.S." Fish and Wildlife Service, Portland, Oregon.