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General Description: Thelypodium repandum is a short-lived biennial or winter annual with a single taproot ranging from 8 - 24 inches tall. Leaves are hairless, bluish-green in color, and somewhat fleshy. Most leaves are basal and petiolate with an oblong blade and wavy margins. Stem leaves are alternate, narrow, untoothed, less than 3 inches long and 0.75 inches wide, lacking petioles, and even somewhat clasping the stem. The inflorescence arises from the center of the basal rosette as a single stem. It may remain unbranched, forming a single-stemmed flowering head, or be branched just above the base. Flowers are light purple to occasionally white, with one to several spike-like (dense racemes) inflorescences. Fruits are spreading to ascending, 1 - 3 inches long, narrow, and slightly flattened. Fruits are technically described as "stipate," an important characteristic in keying plants in the Mustard family. The stipe is the narrowed stalk-like portion of the fruit between the expanded seed-holding portion and the fruit petiole (Elzinga 1996).
Technical Description: Glabrous, glaucous biennial or annual with a simple to rather freely branched, thick stem (but not fistulose), stem (1) 2 - 6 dm tall; leaves all petiolate and not auriculate at the base, rather fleshy, mostly basal or suprabasal the blades 1.5 - 8 cm long, ovate-lanceolate to obovate, sinuate-repand to (the basal) often somewhat lyrate; racemes very densely flowered, typically 2/3 - 4/5 the total height of the plant; ebracteate; pedicels divaricate, 5 - 15 mm long; calyx and corolla lavender-purplish, the sepals narrow, spreading, not saccate at the base, 2.5 - 3.5 mm long; petals narrowly spatulate, barely exceeding the sepals; stamens subequal to the petals, the anthers purple, about 1 mm long; siliques spreading to arcuate-ascending, strongly 1-nerved, 4 - 7 cm long, about 1.5 mm broad, the stipe about 0.5 mm long; style 0.5 - 1 (1.5) mm long; stigma small, not lobed; cotyledons obliquely accumbent (Hitchcock et al. 1964).
Diagnostic Characteristics: Thelypodium repandum is an erect, hairless, glaucous, somewhat fleshy annual or biennial with mostly basal leaves, and a dense raceme(s) of light purple to white flowers. This suite of characters combined with its rocky, sparsely vegetated habitat, make this taxon distinctive.
Infraspecific Taxa: There are no subspecies recognized for Thelypodium repandum.
Similar-appearing Taxa: No congenerics are known to be sympatric with Thelypodium repandum. The only other species of Thelypodium that may occur within the same range and habitat is T. laciniatum. This species has white flowers and basal leaves that are narrow and usually subpinnatifid. Species of Stanleya (S. pinnata, S. tomentosa, and S. viridiflora) may be confused with T. repandum. A key technical difference between the two genera is stipe length, which is usually <6 mm for Stanleya (and often as much as 20 mm long), and <5 mm for Thelypodium.
All of the Stanleya species found in the Challis area are robust plants, sometimes reaching a meter or more in height. The basal leaves of Enceliopsis nudicaulis, a member of the composite family, may be mistaken for T. repandum, in the absence of inflorescences (Elzinga 1996).
Identification of this Taxon in Idaho: Thelypodium repandum is an erect, hairless, glaucous, somewhat fleshy annual or biennial with mostly basal leaves, and a dense raceme(s) of light purple or occasionally white flowers. It is distinctive when in flower.
Global Comments:
Idaho Comments:
Global: Thelypodium repandum is a local endemic of the Challis vicinity in east-central Idaho. It is one of the rarest of the suite of endemic plant species occurring in the area. The species is known from 62 extant occurrences, plus one occurrence that has been extirpated. Most populations are small. Forty of the 62 extant occurrences in the Idaho Conservation Data Center (IDCDC) data base have been reported to contain 10 or less individuals. Only five have been reported as 50 or more individuals. However, populations vary dramatically from year to year. As a general rule, small populations are more at risk of local extirpation due to small scale disturbances than large populations. Because T. repandum is a winter annual-biennial, population sizes are largest in late summer to early fall when individuals from the current year, and new plants that will flower the following year, are both present.
About half of the known occurrences are located adjacent to roads. These populations are vulnerable to road maintenance activities, weed control, and mining activities. These activities have led to the contraction of several populations. At least one population is known to be extirpated from realignment of Highway 75. Mining activities can affect T. repandum in several ways. The most common is removal of scree from the base of slopes containing the species. This has a direct impact on portions of the population at the slope base, and may also affect plants higher on the slope, as the angle and rate of slope movement, increases. Thelypodium repandum often is found in historic hardrock mining districts that may become revitalized as new technology allows the extraction of remaining mineralization.
Impacts from off-road vehicles (ORV) are local, but can be severe within T. repandum habitat. Most ORV use takes place near the town of Challis. Herbicides application to control roadside weed infestations is a threat at some populations. Thelypodium repandum plants killed by roadside herbicide application have been observed. The BLM has found it difficult to coordinate conservation concerns for T. repandum with Custer County spray crews. Knapweed and cheatgrass are found at some T. repandum sites. Leafy spurge also occurs with some populations. Threats from these aggressive weeds has not been assessed.
Grazed and trampled plants have been observed. These effects are generally local, and it seems unlikely that livestock or native animal use cause substantial, direct negative consequences to populations. Herbivory by an unknown lepidopteran can be locally severe.
Of the 63 occurrences for T. repandum, 44 occur on Salmon District, BLM lands, two on the Salmon-Challis National Forest, two on State of Idaho lands, and seven on private land. The exact location of eight populations is unknown, occurring either on BLM lands or adjacent private property. Two populations are protected within the BLM's Germer Basin and Malm Gulch Areas of Critical Environmental Concern/Research Natural Areas.
Thelypodium repandum is an Idaho BLM Sensitive species, and a Region 4, Forest Service Sensitive species. Until the U. S. Fish and Wildlife Service revised their candidate system in early 1996, T. repandum was a Category 2 (C2) candidate for listing under the Endangered Species Act. Under the revised system it is no longer a candidate species. It is ranked globally rare by the Idaho Native Plant Society. Presently, the CDC designation for T. repandum is G3/S3. This indicates that globally, the species is rare or uncommon, but not imperiled. Because it is an Idaho endemic, it has the same state (S) as global (G) rank.
Thelypodium repandum is monitored annually at a number of populations on BLM land. A life history study and seed germination study (Bureau of Land Management 1992) have been completed for the species. A management plan for T. repandum has also been drafted (Atwood no date). A Conservation Agreement between the U. S. Fish and Wildlife Service and BLM was signed in 1990 (Bureau of Land Management 1990), but expired in 1995, and has not been renewed. A Habitat Conservation Assessment and Conservation Strategy are being prepared for T. repandum under contract from the U. S. Fish and Wildlife Service. These documents will be completed during 1996.
Idaho: Thelypodium repandum is on the globally rare plant list maintained by the Idaho Native Plant Society.
Global: Thelypodium repandum is endemic to east-central Idaho. It occurs in Custer and a small portion of Lemhi counties. Populations are found along the Salmon River and lower elevations of its tributaries from Ellis, south to Clayton; along the lower East Fork Salmon River and its tributaries; and south of Challis along the Lost River Range. The species total distribution is approximately 60x20 miles (Elzinga 1996).
Idaho: See Global Distribution comments.
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| Thelypodium repandum habitat |
Elevation (Global): 4900 to 7000 feet
Elevation (Idaho): 4900 to 7000 feet
Global: Thelypodium repandum occurs on moderate to steep, unstable, generally southerly-facing slopes of rocky, gravelly to cindery substrate derived from Challis volcanic and metamorphic rock. Associated vegetation is sparse (5 - 20% cover), and bare ground coverage is high. Common associates include Chaenactis douglasii, Enceliopsis nudicaulis, Phacelia hastata, Cryptantha interrupta, Elymus ambiguus var. salmonensis, Oryzopsis hymenoides, and Atriplex confertifolia. Elevations range from 4,900 to 7,000 feet, with most populations found below 6,000 feet elevation. The species is found on road cuts and fills, although these are often colonized from portions of the population further upslope.
Idaho: See Global Habitat comments.
Global: The life cycle of Thelypodium repandum exceeds 12 months, technically making the species a biennial, but because it germinates in the fall, it more closely resembles a winter annual. Most of the seed crop is released after the main germination period, but it is possible that some seed germinates late in the fall and produces seed the following year, a true annual life cycle. It is likely, however, that some after-ripening or dormancy breaking mechanism prevents many seeds from germinating the year they are produced.
Mortality can occur at any time of the year, but is highest in winter. Freezing damage may be responsible for much of the loss. Snow cover at the elevations where T. repandum occurs is sparse. Unprotected by snow cover, plants are exposed to hard freezing temperatures. Once rosettes have survived the winter, they usually become reproductive. It is also adapted to hot, dry summer climatic condition. Climatic variation appears to have an effect on the size of populations from one year to the next, a pattern not uncommon for annual species. Populations tend to be small and comprised of scattered plants.
Thelypodium repandum occurs on unstable slopes that undergo natural disturbance due to steepness and low vegetative cover. It is often found in erosion trails mostly caused by breakage of bedrock outcrops and slope slippage. Thelypodium repandum also has shown a flush of germination after minor road maintenance caused slope movement on a roadcut. Extreme erosion, however, appears to be detrimental, as it does not occur on actively moving slopes. Thelypodium repandum occurs in open communities with sparse vegetation comprised of few species. Such a restricted habitat may be indicative that it is a poor competitor.
Idaho: See Global Ecology comments.
Global: Reproduction is strictly by seed. Seed production can be prolific, over 20,000 seeds per plant (Elzinga 1996). Aborted flowers have not been observed in Thelypodium repandum. It is unknown if T. repandum requires a pollinator under natural conditions. Manipulative experiments showed it is self-compatible (Al-Shehbaz 1973), but floral morphology does not appear conducive to selfing. The species' showy flowers suggests an insect pollinator. Bees and butterflies have been observed visiting flowers. In some populations, ants are found abundantly on plants throughout the flowering season, as well as later in the year. It is uncertain if ants play any role in pollination or seed dispersal. No dispersal mechanisms have been documented. Habitat across the species' range is discontinuous, so seeds must be dispersed in some manner. Al-Shehbaz (1973) notes that the small seed size of the genus Thelypodium suggests wind dispersal. Biotic dispersal mechanism have also been postulated (Elzinga 1996).
It is clear that T. repandum forms a seedbank. It has been observed to reappear at a site after being absent for several years. In germination trials, no pretreatment was required to germinate seed after five months of storage. However, germination percentages increased over an additional six month period, suggesting an after-ripening requirement. Although germination occurred over the range of temperatures tested, it was highest at 300 C, and consistency lower at 50 C. Thelypodium repandum most readily germinated under moist conditions. The ecological implications of these germination trials is that T. repandum can respond to warm, moist conditions very rapidly (within four days). These conditions are most likely to be met in the late summer or fall after a ground-soaking rain shower. Such weather conditions occur erratically in the Challis area, both temporally and spatially (Elzinga 1996).
Idaho: See Global Reproductive comments.
Phenology (Idaho): Germination occurs between July and October. These seedlings overwinter as rosettes, 2 - 30 cm in diameter. They initiate reproduction in May of the following year. Seed ripe initiates by middle to late July, and by mid-August, most of the seed capsules have split and released seed.
Global: Thelypodium repandum is perhaps the rarest of the suite of species endemic to the Challis area in east-central Idaho. Populations tend to be local and comprised of relatively few plants. Many are vulnerable to threats related to road maintenance, weed control, and mining activity. One occurrence was extirpated during a realignment project along Highway 75. Of the 63 occurrences known for T. repandum, 44 occur on Salmon District, BLM lands, two on the Salmon-Challis National Forest, two on State of Idaho lands, and seven on private land. The exact location of eight populations is unknown, occurring either on BLM lands or adjacent private property. Two populations are protected within the BLM's Germer Basin and Malm Gulch Areas of Critical Environmental Concern/Research Natural Areas. Thelypodium repandum is monitored annually at a number of populations on BLM land. A life history study and seed germination study (Bureau of Land Management 1992) have been completed for the species. A status report for T. repandum was originally compiled by Packard (1979). A more comprehensive revised status report was completed in 1988 (Caicco 1988). The BLM has conducted additional surveys since that time.
A Conservation Agreement between the U. S. Fish and Wildlife Service and the BLM for T. repandum was signed in 1990. It expired in 1995, and has not been renewed. To varying degrees, some, but not all portions of the Conservation Agreement were implemented while it was in force. As part of the Idaho Conservation Effort, a Habitat Conservation Assessment and Conservation Strategy for T. repandum are being prepared. They are scheduled for completion during 1996. The specific objectives of the Conservation Strategy are to:
Thelypodium repandum is an Idaho BLM Sensitive species, and a Region 4 Forest Service Sensitive species. As such, it is subject to special management considerations that will maintain the species' viability on lands these agencies administer. Prior to the U. S. Fish and Wildlife Service's recent revision of their candidate system, T. repandum as a category 2 (C2) candidate for listing under the Endangered Species Act. Under the revised system it is no longer considered a federal candidate.
Idaho: See Global Management comments.
General Comments (Idaho): Fairly intensive survey work was conducted in 1988, by both the BLM and Idaho Conservation Data Center. In another intensive effort, approximately 700 polygons of potential habitat on BLM lands were located on aerial photographs. Field checks were completed on a 20% random sample of these (Elzinga 1996).
Inventory Needs (Idaho): Populations are local and small, and it is likely there are additional sites not yet discovered (Elzinga 1996). Caicco (1988) listed areas west of Clayton as worthy of additional survey.
Al-Shehbaz, I. A. 1973. The biosystematics of the genus Thelypodium (Cruciferae). Contributions from the Gray Herbarium 204: 3-48.
Atwood, D. [n.d.]. Management Plan for Thelypodium repandum (wavy-leaf thelypody). Draft.
Bureau of Land Management. 1990. Conservation Agreement for Thelypodium repandum, wavy leaf thelypody.
Bureau of Land Management and USDA-ARS. Interim report FY-1992: general requirements of Thelypodium repandum, a federal C2 species in east-central Idaho. Cooperative study between USDA ARS, Northwest Watershed Research Center and USDI Bureau of Land Management, Salmon District Office. 10 pp. plus tables and figures.
Caicco, S. L. 1988. Status report for Thelypodium repandum. Prepared for: Idaho Department of Parks and Recreation. Idaho Department of Fish and Game, Conservation Data Center, Boise. 35 pp. plus appendices.
Elzinga, C. 1996. Habitat Conservation Assessment and Conservation Strategy for wavy-leaf thelypody (Thelypodium repandum). Draft.
Hitchcock, C. L., A. Cronquist, M. Ownbey, and J. W. Thompson. 1964. Vascular plants of the Pacific Northwest. Part 2: Salicaceae to Saxifragaceae. University of Washington Press, Seattle. 597 pp.
Packard, P. L. [n.d.]. Status report for Thelypodium repandum. 7 pp.
Author: M. Mancuso
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