Santa Clara Valley Dudleya

Dudleya setchellii

Description

Santa Clara Valley dudleya, Dudleya setchellii, is a low-growing perennial of the stonecrop family (Crassulaceae) with fleshy, glabrous leaves. The oblong to triangular, slightly glaucous leaves are 1-3 in (2.5-7.6 cm) long and 0.3-0.6 in (0.75-1.5 cm) wide. Two or three flowering stems ascend to heights of 2-8 in (5-20.3 cm) in mid to late spring. The pale yellow petals are 0.3-0.5 in (0.75-1.3 cm) long. There are two related species in the area. D. cymosa ssp. cymosa, canyon liveforever, has bright yellow to red petals rather than pale yellow, and is, therefore, easily distinguished from D. setchellii with its pale yellow flowers. D. cymosa ssp. paniculata can be distinguished from D. setchellii by its oblong leaves-in contrast to the oblong-triangular leaves of D. setchellii ; its greater degree of rebranching of the inflorescence branches; and its longer pedicels. Santa Clara Valley dudleya is a perennial herb which flowers from May to June and produces wind-dispersed seeds. The species can also reproduce vegetatively by forming rosettes that can separate from the parent plant or remain attached. Because an individual plant can have up to 10 rosettes attached, obtaining an accurate number of true individual plants can be difficult. Individual plants may live for approximately 10 years. They are susceptible to heavy frosts but can survive for up to two years in inhospitable conditions and still exhibit minimal stress. Rock outcrops in a Santa Clara Valley dudleya site usually number from one to 100 with 30-60 plants on each. Few detailed data on the reproductive biology or demography of the species are available. Seedling germination seems to be high in wet years, but seedling survivorship is often very low in both natural and created habitats. Seedling survival is generally less than 5% and may be less than 1% after the first year. The highest survival rates have been observed on east-and north-facing slopes because of the number of rock crevices with enough soil to provide the necessary nutrient and moisture conditions.

Habitat

Santa Clara Valley dudleya is restricted to rocky outcrops within serpentine grasslands between 390 and 990 ft (118.9 and 301.8 m) in Santa Clara county. The roots of Santa Clara Valley dudleya are at least 6 in (15.2 cm) long and often extend into rock crevices of the serpentine outcrops. The narrow distribution of Santa Clara Valley dudleya may be associated with the limited number of appropriate rock crevices available.

The potential habitat for Santa Clara Valley dudleya cannot be determined by counting the number of rock outcrops because only some have crevices deep enough to provide habitat. The rock outcrops themselves have very little vegetative cover but the serpentine grassland where Santa Clara Valley dudleya occurs is often dominated by significant plant communities.

Distribution

Santa Clara Valley dudleya is found only in the Coyote Valley area, from San Jose south about 20 mi (32.2 km) to San Martin in Santa Clara county. Twenty populations are currently documented at the California Natural Diversity Data Base. Almaden Quicksilver County Park contains the three most recently discovered. The species was also identified in April 1997 at the Santa Clara county population of Tiburon paintbrush.

Threats

Santa Clara Valley dudleya has always been restricted to the Coyote Valley area of Santa Clara county. The species is threatened by development, landfill activities, unauthorized dumping, quarry expansion, and off-road vehicles. Sixteen of the 20 known populations are partially or wholly on private land, and most are subject to various levels of threat from development. The northernmost locations in southeastern San Jose and the southernmost locations in the area around Morgan Hill, approximately 17 mi (27.3 km) southeast of San Jose, are at greatest risk. One of the northern populations is threatened with the proposed Cerro Plata project, consisting of 550 dwelling units and a 164-acre (66.4-hectare) golf course on a 575-acre (232.7-hectare) site. One estimate suggested this population contains approximately 20,000 plants, or 61% of all known plants, of which approximately 2,380 would be directly eliminated by planned construction activities. All remaining plants would be exposed to human activities during and after construction that would result in significant threats to the population. These impacts include potentially harmful runoff from an upslope golf course, introduction of weedy species during construction, and uncontrolled foot traffic.

Another of the northern sites was threatened by the proposed construction of the Valley Christian School and South Valley Christian Church. As originally proposed, this construction would have eliminated 74% of the approximately 1,900 Santa Clara Valley dudleya plants found on the site. A revised plan indicates that the majority of the plants will be avoided. Approximately 700 additional mature plants have been translocated to an area near the base of the north slope of the project site. Santa Clara Valley dudleya plants were individually removed from rocks. The serpentine rocks where the plants had grown were moved, a new serpentine rock habitat created, and the plants translocated. The translocated Santa Clara Valley dudleya will be monitored for 10 years. Two f the more centrally located populations of Santa Clara Valley dudleya are also threatened with imminent development, including residential development adjacent to Tulare Hill and road construction in Metcalf Canyon. One central population, due to its proximity to an off-road motorcycle park, may be threatened by off-road motorcycle traffic and unauthorized dumping. The Kirby Canyon Landfill, located approximately 3 mi (4.8 km) north of Morgan Hill and operated by Waste Management of California, Inc., is expected to eliminate approximately 1,240 plants during its service life of 50 years. The remaining two populations that occur on private land in the center portion of the species' range are on the grounds of the IBM Bailey Avenue laboratory. The company apparently plans to preserve the habitat. In addition to development, grazing and collecting may threaten Santa Clara Valley dudleya. Grazing occurs on much of the grassland where Santa Clara Valley dudleya is located and may result in reduced vigor or death of mature D. setchellii individuals and the failure of seedling establishment. Unrestricted collecting for scientific or horticultural purposes or excessive visits by individuals interested in seeing rare plants could threaten Santa Clara Valley dudleya. Due to the slow growth rate of this species and the rarity and desirability of large succulents, mature plants found in the wild are particularly susceptible to collection.

Conservation and Recovery

Recovery of Santa Clara Valley dudleya must first focus on protecting and managing extant populations. Populations on private land should be protected by land acquisition, conservation easements, or other means. Protection of populations on public land will involve working with the Santa Clara County Parks Department to ensure the long-term survival of the species on their lands.

Contact

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. 1998. "Recovery Plan for Serpentine Soil Species of the San Francisco Bay Area." Portland, Oregon. 330+ pp.