Endangered Species Recovery Program

E. San Joaquin Woolly-Threads (Lembertia congdonii)

• 1. Description and Taxonomy
  • Taxonomy
  • Description
  • Identification
• 2. Historical and Current Distribution
  • Historical Distribution
  • Current Distribution
• 3. Life History and Habitat
  • Reproduction and Demography
  • Habitat and Community Associations
• 4. Reasons for Decline and Threats to Survival
  • Reasons for Decline
  • Threats to Survival
• 5. Conservation Efforts
• 6. Recovery Strategy

1. Description and Taxonomy

Taxonomy.-- In 1883, Gray named San Joaquin woolly-threads as Eatonella congdonii. The type specimen had been collected by Congdon near Deer Creek (Tulare County) in that same year. The current name, Lembertia congdonii, was published by Greene in 1897, who determined that San Joaquin woolly-threads should be separated from snowy eatonella (Eatonella nivea). Subsequent taxonomists have upheld Greenes taxonomy (Johnson 1993, Taylor 1989). San Joaquin woolly-threads is the sole species in the genus Lembertia, which is in the aster family (Asteraceae).

Description.-- The common name "woolly-threads" is derived from the many long (up to 45 centimeters; 18 inches), trailing stems covered with tangled hairs. However, San Joaquin woolly-threads plants also can be tiny (less than 7 centimeters; less than 3 inches) and erect with a single stem (Cypher 1994a). The tiny, yellow flower heads are clustered at the tips of the stems and branches (Figure 13). Each flower head is approximately 6 millimeters (0.25 inch) long and contains two types of florets (the tiny flowers characteristic of the aster family); the four to seven outer florets differ in shape from the numerous inner florets. The two types of florets produce achenes (tiny, one-seeded fruits) that also differ in shape (Johnson 1993, Taylor 1989).

Identification.-- San Joaquin woolly-threads differs from snowy eatonella in the shape of the florets and achenes and in geographical range (Munz and Keck 1959, Johnson 1993, Taylor 1989).

Figure 13. Illustration of San Joaquin woolly-threads (from Abrams and Ferris Vol. 4, 1960, with permission).

2. Historical and Current Distribution

Historical Distribution.-- The historical range of San Joaquin woolly-threads is based on 47 herbarium specimens and literature reports dating from 1883 to 1983; 30 of the occurrences were from the floor of the San Joaquin Valley, four were from the Cuyama Valley, and the remainder were in the hills west of the San Joaquin Valley (Figure 14). These occurrences were concentrated in eight areas (in descending order of abundance): (1) the plains between Avenal and Mendota in Kings and Fresno Counties, (2) from Bakersfield to Shafter in Kern County, (3) the inner Coast Ranges of western Fresno and eastern San Benito Counties, (4) from north of Lokern to Lost Hills in Kern County, (5) the Carrizo and Elkhorn Plains in San Luis Obispo County, (6) the Cuyama Valley in Santa Barbara County, (7) east of Edison in Kern County, and (8) the type locality. However, 33 of the historical occurrences had been eliminated by 1989 (Taylor 1989).

Current Distribution.-- Many new occurrences of San Joaquin woolly-threads have been discovered since 1986, primarily in the hills and plateaus west of the San Joaquin Valley. These constitute four metapopulations and several small, isolated populations. The largest metapopulation occurs on the Carrizo Plain Natural Area, where the occupied habitat totaled over 1,100 hectares (2,800 acres) in 1993 (R. Lewis 1993), which was a particularly favorable year. In years of lower rainfall, the occupied area is much smaller (E. Cypher unpubl. observ.). Much smaller metapopulations are found in Kern County near Lost Hills, in the Kettleman Hills of Fresno and Kings Counties, and in the Jacalitos Hills of Fresno County. The isolated occurrences are known from the Panoche Hills in Fresno and San Benito Counties, the Bakersfield vicinity, and the Cuyama Valley (CDFG 1995, Taylor 1989, Stebbins et al. 1992, R. Lewis 1993, Taylor and Buck 1993, USBLM in litt. 1994, S. Carter pers. comm., R. Lewis pers. comm., S. Wilson pers. comm.).

Figure 14. Distribution of San Joaquin woolly-threads (Lembertia congdonii).

3. Life History and Habitat

Reproduction and Demography.-- San Joaquin woolly-threads is an annual herb, and its phenology varies with weather and site conditions. In years of below-averae precipitation, few seeds of this species germinate, and those that do typically produce tiny plants. Seed germination may begin as early as November but usually occurs in December and January. San Joaquin woolly-threads typically flowers between late February and early April, but flowering may continue into early May if conditions are optimal (B. Delgado pers. comm.). Populations in the northern part of the range flower earlier than does the Carrizo Plain metapopulation. Each plant may have from 1 to more than 400 flower heads. Seed production depends on plant size and the number of flower heads; in 1993, achene production ranged from 10 to 2,500 seeds per individual (Mazer and Hendrickson 1993b, Cypher 1994a, E. Cypher unpubl. data). The seeds are shed immediately upon maturity, and all trace of the plants disappears rapidly after their death in April or May. Seed dispersal agents are unknown, but possible candidates include wind, water, and animals. Seed-dormancy mechanisms apparently allow the formation of a substantial seed bank in the soil (Twisselmann 1967, Taylor 1989, R. Lewis 1993, Mazer and Hendrickson 1993b, Cypher 1994a).

Insect pollinators are not required for seed-set in San Joaquin woolly-threads (Mazer and Hendrickson 1993b). However, animals may be important to this plant species in other ways. On the Carrizo Plain Natural Area, giant kangaroo rat activity contributes to greater plant size and flower head production in San Joaquin woolly-threads, probably by increasing available soil nutrients and reducing competition from other plants. The microhabitat offered by giant kangaroo rat precincts also contributes to earlier seed germination and maturation of San Joaquin woolly-threads, possibly because precinct surfaces are warmer than the surrounding area during the winter months (Cypher 1994a, 1994b).

Habitat and Community Associations.-- San Joaquin woolly-threads occurs in Nonnative Grassland, Valley Saltbush Scrub, Interior Coast Range Saltbush Scrub, and Upper Sonoran Subshrub Scrub (Cypher 1994a). This species typically occupies microhabitats with less than 10 percent shrub cover, although herbaceous cover may be either sparse or dense, and cryptogamic crust may or may not be present. Plant species that often occur with San Joaquin woolly-threads include red brome, red-stemmed filaree, goldfields, Arabian grass (Schismus spp.), and mouse-tail fescue (Vulpia myuros). Hoovers woolly-star often occurs in populations of San Joaquin woolly-threads, although the reverse is not true (Taylor 1989, R. Lewis 1993, Taylor and Buck 1993, Cypher 1994a). In two cases, San Joaquin woolly-threads was found at low densities in previously disced areas that were adjacent to undisturbed populations (R. Lewis 1993, Taylor and Buck 1993).

San Joaquin woolly-threads occurs on neutral to subalkaline soils that were deposited in geologic times by flowing water. On the San Joaquin Valley floor, this species typically is found on sandy or sandy loam soils, particularly those of the Kimberlina series, whereas on the Carrizo Plain it occurs on silty soils. San Joaquin woolly-threads frequently occurs on sand dunes and sandy ridges as well as along the high-water line of washes and on adjacent terraces. Occurrences have been reported at elevations ranging from approximately 60 to 260 meters (200 to 850 feet) on the Valley floor and surrounding hills, and from 600 to 800 meters (2,000 to 2,600 feet) in San Luis Obispo and Santa Barbara Counties (Hoover 1937, CDFG 1995, Taylor 1989, R. Lewis 1993, Taylor and Buck 1993, E. Cypher unpubl. observ., R. van de Hoek pers. comm.).

4. Reasons for Decline and Threats to Survival

Reasons for Decline.-- Habitat loss was responsible for the decline of San Joaquin woolly-threads on the floors of the San Joaquin and Cuyama Valleys, where the majority of the occurrences were eliminated by intensive agriculture. In addition, several sites in and around Bakersfield were eliminated by urban development, and two others between Lokern and Lost Hills apparentl were destroyed as a result of intensive oilfield development (CDFG 1995, Taylor 1989).

Threats to Survival.-- The Lost Hills metapopulation is on private land in an area of high value for commercial development and agriculture (Taylor 1989, Taylor and Buck 1993). Several occurrences in the Kettleman Hills, the Jacalitos Hills, and west of Bakersfield are in low-density oilfields; the plants do not seem to be threatened by the current level of activity but could be destroyed by more intensive use of the areas (R. Lewis 1993, E. Cypher unpubl. observ.). Preliminary studies suggested that both competition from exotic plants and spring grazing reduced survival rates, but not flower production, in San Joaquin woolly-threads (E. Cypher unpubl. data). Trampling also reduces survival in areas where livestock congregate, such as around water troughs (Taylor 1989, R. Lewis 1993, Mazer and Hendrickson 1993b, Cypher 1994a,b, E. Cypher unpubl. data, B. Delgado pers. comm.). However, removal of livestock from areas that have been grazed continuously for decades would be inadvisable without additional data, because grazing may in fact be a useful management tool to control competition from exotic plants (E. Cypher unpubl. observ.).

5. Conservation Efforts

San Joaquin woolly-threads was federally listed as endangered in 1990 (USFWS 1990; Table 1). USBLM biologists have conducted extensive surveys for San Joaquin woolly-threads. Thus, many of the occurrences that are known currently are on lands administered by USBLM, including the entire Carrizo Plain Natural Area metapopulation, part of the Kettleman Hills metapopulation, and the sites in the Jacalitos and Panoche Hills. Within these areas, fences have been erected around several small occurrences of San Joaquin woolly-threads that showed evidence of trampling by livestock (R. Lewis 1993, S. Carter pers. comm., B. Delgado pers. comm.). The Carrizo and Elkhorn Plains and the Kettleman Hills are within Areas of Critical Environmental Concern, which would restrict activities on USBLM lands in those regions (USBLM 1996a,b). USBLM and the Endangered Species Recovery Program are cooperatively monitoring selected populations and conducting research on the impacts of livestock grazing (Cypher 1994a,b, USBLM in litt. 1994).

Other groups also are contributing to conservation of this species. CDFG funded research on the demography, reproductive biology, and ecology of San Joaquin woolly-threads (Mazer and Hendrickson 1993b, Cypher 1994a). California Energy Commission, U.S. Department of Energy, and California Department of Water Resources have sponsored surveys for rare plants, including San Joaquin woolly-threads, in various parts of the southern San Joaquin Valley (Anderson et al. 1991, Stebbins 1993, B.L. Cypher pers. comm.). The Metropolitan Bakersfield Habitat Conservation Plan identified a 121-hectare (300-acre) area west of Bakersfield as a preserve acquisition target for this species (Metropolitan Bakersfield Habitat Conservation Plan Steering Committee 1994). If the Kern County Valley Floor Habitat Conservation Plan is implemented as currently proposed, private landowners in the vicinity of Lost Hills would be offered incentives to protect San Joaquin woolly-threads habitat (T. James pers. comm.).

6. Recovery Strategy

The recovery goal for San Joaquin woolly-threads is similar to that for the other endangered plant species in this plan: to maintain self-sustaining populations in protected areas representative of the former geographic and topographic range of the species and in a variety of appropriate natural communities. A sufficient number of natural populations exist that reintroduction should not be necessary, provided that the existing sites are protected and managed properly. Unoccupied habitat within metapopulations also should be protected to allow for population fluctuations with rainfall and to facilitate seed dispersal. Thus, additional elements of the strategy are to protect land in blocks of at least65 hectares (160 acres), which have an average density of at least 1,000 San Joaquin woolly-threads plants per hectare (400 plants per acre); and to avoid fragmenting any metapopulation into more than 2 blocks of contiguous, protected natural land. Finally, buffer zones of 150 meters (500 feet) or more should be protected beyond the population margins to reduce external influences and to allow for population expansion.

The top-priority task to ensure the survival of San Joaquin woolly-threads is to protect existing habitat in the San Joaquin Valley. Other actions that are necessary for recovery include protection and appropriate management of populations on public land and annual monitoring of representative sites within each metapopulation. Monitoring is particularly important in some of the smaller populations, including the Lost Hills, Jacalitos Hills, and Kettleman Hills metapopulations and the Panoche Hills population to determine whether densities are increasing, decreasing, or remaining stable. Monitoring can verify that existing management strategies are having the desired effect or draw attention to incompatible land uses.