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General Description: Salmon twin bladderpod has a large, thick taproot, surmounted by a tight rosette of silvery leaves. The leaves are spatulate-shaped, the blade gradually tapering to a winged petiole that is often lyrate (pinnately lobed, with the terminal lobe the largest and rounded). The few-flowered inflorescence occurs on a long, thin, generally curving stem. The yellow flowers produce large, inflated fruits that are obviously bilocular (Moseley et al. 1990).
Technical Description: Heavy-rooted perennial, often with a branched caudex,silvery-stellate, the hairs not closely appressed; stems usually many, somewhat decumbent-based, 2 - 17 cm long; basal leaves numerous, rosulate, marcesent, 2 - 8 cm long, the blades obovate or broadly oblanceolate to somewhat rhombic or even ovate, mostly obtuse, usually with a few inconspicuous to prominent teeth or entire, narrowed rather gradually to broad, winged, mostly lyrate, petiole-like bases about as long as the blades; cauline leaves several, reduced, mostly oblanceolate and entire; racemes somewhat closely flowered; pedicels slender to rather stout, 7 - 18 mm long, ascending, straight or somewhat curved but not sigmoid; lateral sepals not saccate at the base; petals yellow, broadly spatulate–obovate, 9 - 12 mm long; silicles much-inflated, 15 - 20 mm long and at least as broad, didymous, the base very slightly cordate, the apical sinus narrow, nearly closed, 2 - 4 mm deep; replum obovate to oblanceolate, more nearly obtuse than acute at the apex, 3 - 6 mm long, 2 - 3 mm broad; style 6 - 9 mm long; seeds 2 - 3 per locule (Hitchcock et al. 1964).
Diagnostic Characteristics: The tight rosette of silvery basal leaves quickly distinguishes this species from most others members of the east-central Idaho flora. The genus Physaria is most likely to be confused with the related genus Lesquerella. The fruits (silicles) of Physaria are usually didymous, or at least with a prominent apical sinus 2 - 4 mm deep, a character absent in Lesquerella. The large size of the inflated valves of the mature silicles, (12)15 - 20 mm long, and the fruits not being strongly obcompressed, are the most reliable field characteristic to distinguish Physaria didymocarpa var. lyrata from other congeners occurring in east-central Idaho. Although the varietal epithet refers to the lyrate petioles, this character is not a constant feature that can be used definitively to distinguish between the infraspecific taxa of P. didymocarpa.
Chromosomal studies by Mulligan (1968), who apparently was unaware of Hitchcock's (1964) then recent description of var. lyrata, found that Physaria didymocarpa from low elevations near Salmon represented a different chromosome race than other P. didymocarpa taxa. The two counts he made from plants around Salmon were hexaploid (2n = 24), while all other P. didymocarpa taxa were diploid or tetraploid. The higher ploidy level of var. lyrata isconsistent with morphological data and other observations collected for this taxon. The var. lyrata is consistently larger in size than var. didymocarpa. Gigantism is a common characteristic of higher ploidy levels within groups of closely related species.
Infraspecific Taxa: Physaria didymocarpa var. didymocarpa.
Similar-appearing Taxa: No other Physaria taxa are known to be sympatric with Salmon twin bladderpod. Two taxa do, however, occur elsewhere in east-central Idaho, and may cause some confusion: Physaria geyeri and Physaria didymocarpa var. didymocarpa.
Physaria geyeri is represented in central Idaho by two varieties, the widespread var. geyeri, and the Lemhi and Custer county endemic, var. purpurea. Because var. purpurea was once considered a rare plant, surveys were conducted by botanists from the University of Idaho Herbarium. They found it did not occur east of the Challis Creek and Camas Creek drainages. Physaria geyeri has not been observed in the Lemhi and Salmon river valleys near Salmon. Physaria geyeri can be distinguished from P. didymocarpa by its strongly obcompressed, only slightly inflated fruits.
Physaria didymocarpa var. didymocarpa occurs at high elevations, largely alpine, in the southern Beaverhead Mountains and on the east slope of the southern Lemhi Range. The length of mature silicles for var. didymocarpa, are generally significantly smaller than the average found in populations of the var. lyrata.
Although the varietal epithet refers to the lyrate petioles, this character is not a constant feature that can be used definitively to distinguish between the two P. didymocarpa taxa. As reported by Rosentreter (1982) and used by Hitchcock et al.(1964) in his keys, the most distinguishing feature is mature fruit size. Variety didymocarpa has valves 8 - 12 (15) mm long as compared with var. lyrata that has valves (12) 15 - 20 mm long. However, Rosentreter (1982) often found immature unpollinated, or poorly developed fruits on the infloresences that measured less than 12 mm in length.
Identification of this Taxon in Idaho: Mature fruits are required for positive identification. Physaria didymocarpa var. lyrata is also geographically separated from similar-looking species that occur in east-central Idaho.
Global Comments:
Idaho Comments: The validity of this taxon has been questioned in the past, but this is no longer the case.
Global: Physaria didymocarpa var. lyrata is a rare taxon endemic to the Salmon area in east-central Idaho. This taxon was described in 1964, and for many years was known only from the type locality on Williams Creek. Because of this, it was made a federal Category 2 candidate for listing under the Endangered Species Act. Due to its rarity, P. didymocarpa var. lyrata was recommended for threatened status when it was evaluated as part of the Idaho rare plant project of the Idaho Natural Areas Council. This recommendation was later changed to endangered due to habitat destruction taking place at the Williams Creek site. The conservation of P. didymocarpa var. lyrata has been addressed by a series of Conservation Agreements between the U. S. Fish and Wildlife Service and the BLM. The initial Conservation Agreement was signed in 1984 (U. S. Fish and Wildlife Service 1984). A new Conservation Agreement was signed in 1990 (Elzinga 1990). This expired in 1995, and has not been renewed.
Presently, P. didymocarpa var. lyrata is known from seven occurrences, supporting an estimated total of 5,000 plants. Population numbers vary from less than 100 to approximately 3,000, with only three populations estimated to contain 1,000 or more plants. All occurrences are local in extent. A population and habitat study was conducted between 1991 and 1995, at four populations (Pattee Creek 001, Williams Creek 002, Agency Creek 003, and Basin Creek 004). Analysis of life history stages, mortality, and recruitment at these four occurrences indicates that, in the long-term, the Williams Creek and Agency Creek populations are probably the least stable. They have fewer individuals, and the substrate at the Williams Creek site is very unstable, making it especially susceptible to disturbance. Pattee Creek is the largest and apparently the most stable of the study populations. However, this population is comprised largely of relatively recently recruited individuals, which tend to be more vulnerable to environmental stresses. The Basin Creek population also appears stable.
Other findings include, that small plants, particularly seedlings have a higher mortality rate than larger plants. Well established (large) plants are apparently able to survive more environmental stress than small plants. Therefore, plant size is an important attribute when determining population demographics. The recruitment of seedlings in all study populations after years in which few plants were reproductive, indicates the presence of at least a short-term seed bank. During the study, weather conditions were a major factor in determining the short-term fate of individual plants. The total number and density of Physaria didymocarpa var. lyrata plants fluctuated yearly with the amount of spring and summer precipitation. Numbers decreased in dry years and increased in wet ones. All the study populations, except Pattee Creek, show a general downward trend in reproducing plants from 1991 to 1995, although the proportion of established (non-seedlings) plants that reproduced each year, remained fairly constant, except at Williams Creek. Elimination of reproducing plants at Williams Creek was the result of substrate movement during periods of heavy rain. All life stages were present at each site, each year, except Williams Creek. Photodocumentation monitoring at the Williams Creek population began in 1986, and the trend appears to be stable to slightly downward (Elzinga 1990).
All populations of Physaria didymocarpa var. lyrata have been disturbed to some degree in the past, and each faces some level of ongoing, human-influenced disturbance. Habitat modification or destruction related to materials removal, and road construction and maintenance have been documented. Roadside herbicide spraying has been identified as a potential threat. Recent studies (Craig 1996) indicate that cheatgrass (Bromus tectorum) is presently not a major competitor of P. didymocarpa var. lyrata, as was previously suggested (Rosentreter 1982; Elzinga 1990). Livestock grazing occurs at all but the Williams Creek site, but does not appear to be a major threat (Craig 1992; 1996). Several specific threats have been identified for Physaria didymocarpa var. lyrata.
Mineral exploration has occurred throughout the area supporting the Pattee Creek population (001). Because major exploration would require road maintenance, mining activity in the area would likely impact at least portions of the population. The Williams Creek population (002) is located in an area that was a community material pit for many years. Under terms of an earlier Conservation Agreement (U. S. Fish and Wildlife Service 1984), shale removal was limited to portions of the pit where there were no P. didymocarpa var. lyrata plants. In February 1990, excessive material removal by users resulted in a decision by the BLM to close the pit. The area of the pit containing plants has been fenced and signed. At the Agency Creek (003) occurrence, some individual plants are threatened by minor road maintenance and roadside spraying. Several plants were removed by placement of a county road sign in 1989. Major road work could possibly eradicate much of this population. Most of the Basin Creek population (004) is undisturbed, with the exception of cattle trails and one old road and cutbank. No threats or special management concerns have been identified for the Bear Valley Creek (005) population. Cattle grazing occurs at the Dry Creek (006) and Lake Creek (007) populations, but is not considered a threat to P. didymocarpa var. lyrata.
Six of the seven known occurrences are located on land managed by the BLM's Upper Columbia-Salmon Clearwater Districts, Lemhi Resource Area. A portion of one of these populations (Basin Creek, 004) extends onto adjacent private land. One occurrence (Bear Basin Creek, 005), discovered in 1992, is located on the Leadore Ranger District, Salmon National Forest. Physaria didymocarpa var. lyrata is an Idaho State BLM Sensitive Species. It was originally added to the Forest Service Region 4, Salmon-Challis National Forest Sensitive Species list prior to the species' discovery on Forest land due to the close proximity of most populations to the Forest.
Until the U. S. Fish and Wildlife Service recently revised their candidate system, P. didymocarpa var. lyrata was a category 2 candidate. Under the revised system it is no longer considered a federal candidate species. At the 1994 Idaho Rare Plant Conference it was recommended for federal category 1 (C1) status. The Idaho Native Plant Society presently includes this species on its list of globally rare taxa. The Idaho Conservation Data Center currently ranks P. didymocarpa var. lyrata as G5T1 S1 [G5 = Physaria didymocarpa is demonstrably secure; T1 = var. lyrata is critically imperiled throughout its range because of extreme rarity or because of some other factor of its biology making it vulnerable to extinction; S1 = because var. lyrata is endemic to Idaho, the state (S) rank equals the global rank for the taxon (T)].
Idaho:
Global: A narrow endemic known only from the Salmon and Lemhi river valleys near the town of Salmon, Lemhi County, in east-central Idaho.
Idaho: See Global Distribution comments.
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| Physaria didymocarpa lyrata habitat |
Elevation (Global): 4500 to 6800 feet
Elevation (Idaho): 4500 to 6800 feet
Global: Physaria didymocarpa var. lyrata occurs on rocky, sparsely vegetated, gentle to steep southerly slopes. It can be found from upper to lower slope positions. Vegetation cover is low and bare ground and rock coverage high. The substrate is dominated by rocks 1 - 3 inches in diameter, and can be loose, or more often fairly stable. Parent material consist of rocks belonging to the Challis Volcanics group. These are undifferentiated andesite and latite flows, quartz latite and rhyolite flows, ignimbrites, and tuffs. Plants can be found in roadcuts and other sites subject to disturbance.
This species occurs in areas of low vegetation cover within the Artemisia tridentata ssp. tridentata/Agropyron spicatum habitat type. Canopy cover of all species is low, usually less than 20%. In study plots, Craig (1996) found that plant species diversity was usually low, averaging less than eight taxa per plot. Associated species include Phacelia hastata, Oenothera caespitosa, Chaenactis douglasii, and Agropyron spicatum. Bromus tectorum is a common associate at some sites as well.
Idaho: See Global Habitat comments.
Global: There is limited specific information regarding the autecology of Physaria didymocarpa var. lyrata. It generally occurs in areas where bare ground or rock coverage is 80% or greater. Rocks 1 to 3 inches in diameter are the dominant size class. The substrate can be loose, but more commonly is somewhat stable, indicating this taxon is adapted to some level of periodic disturbance. Most plants are found on southerly aspects, further indicating this species adaptation to xeric, harsh sites. Vegetation cover is sparse at most sites, rarely exceeding 20%, although it varies from a trace to 70%. Plants do not occur in areas of heavy shrub coverage. In sampled plots, the density of P. didymocarpa var. lyrata varied from 6.5 to 3 plants/square yard (Craig 1992). As part of this same study, it was found that all life stages were represented at each population except one.
Most occurrences consists of several metapopulations, or clusters of plants spatially separated from one another. The total number and density of Physaria didymocarpa var. lyrata plants apparently fluctuate yearly with the amount of spring and summer precipitation. Numbers decrease in dry years and increase in wet ones (Craig 1996). Recruitment of ndividuals varies annually, also increasing with wet and cool weather conditions (Craig 1996). Physaria didymocarpa var. lyrata is just one of several species narrowly endemic to the Challis Volcanics of east-central Idaho. It has been speculated that P. didymocarpa var. lyrata has always been rare (Craig 1992).
Idaho: See Global Ecology comments.
Global: Physaria didymocarpa var. lyrata is an outbreeding species (Mulligan 1968). Reproduction is predominantly by seed. The seeds disperse almost entirely by gravity, although wind sometimes rolls the fruits on the ground for a limited distance (Craig 1992). It is pollinated by non-specific insect vectors; species that do not cover great distances in search of specific flowers (Rosentreter 1982). It is likely that all of the seven known occurrences are reproductively isolated by distance between them. Although there has been no specific research concerning the seed bank of Physaria didymocarpa var. lyrata, studies indicate some seeds must remain dormant throughout at least one growing season and probably longer (Craig 1996). High recruitment levels after years when reproduction was poor and mortality high suggest that visible plants represent only a portion of the population. Good seedling germination was observed in all years when moisture and temperatures were favorable (Craig 1996).
Plants are considered long-lived and possess an extensive tap root that grows upward whenever the plant is covered by moving substrate. This has been likened to a form of layering (Rosentreter 1982). A new whorl of leaves forms after each burial and swellings of the root record the number of times this has occurred. This morphological characteristic indicates the disturbance history at a site. Consequently, a large plant is not necessarily older than a small individual, but may be one that has regrown following disturbance to the overlying substrate. In addition, it has been shown that even plants undisturbed by substrate movement can become smaller between years (Craig 1996). In research conducted by Craig (1996), plants scored as dead one year regrew in later years. As it turned out, they were merely dormant. Results from this research showed that some plants were at least six years old, although few of the original cohorts were still alive after five summers. The average age of non-seedling plants at the Pattee Creek occurrences was 3 years (± 1.4 years). Counting seedlings drops this to 2.1 years (± 1.4 years).
Idaho: See Global Reproductive comments.
Phenology (Idaho): The early season phenology of Physaria didymocarpa var. lyrata is variable, being related to spring weather patterns. Flowering usually begins sometime in May, but appears to be opportunistic. For instance, in 1992, many plants did not flower until after rainstorms in late June. In 1993, when moisture and cool temperatures prevailed all summer, plants also bloomed throughout the summer. Fruits are generally dehiscent by August.
Global: Six of the seven known populations of Physaria didymocarpa var. lyrata occur on BLM land, with part of the Basin Creek population extending onto adjacent private land. One population, discovered in 1992, is located in the Bear Lake Creek drainage on the Salmon National Forest. A Conservation Agreement between the U. S. Fish and Wildlife Service and the BLM, addressing the conservation of this taxon expired in 1995. The primary actions agreed to in the expired conservation Agreement Elzinga 1990) are that efforts will be made by the BLM to remove threats facing P. didymocarpa var. lyrata, and to implement site specific management plans to protect the species.
The BLM sponsored a demographic and habitat characterization study covering the four populations known prior to 1992 (Craig 1992; 1996). Based on results of this study, Craig (1996) recommended protection of known populations from additional human-induced disturbance to be the bet management approach. If deemed necessary, a seed collection and storage plan is also noted.
Idaho: See Global Management comments.
General Comments (Idaho): The range of Physaria didymocarpa var. lyrata has been thoroughly surveyed over the past 15 years by botanists from the University of Idaho Herbarium, Conservation Data Center (see Moseley et al. 1990), and especially the BLM. Additionally, personnel associated with the Salmon National Forest have also searched for this species.
Inventory Needs (Idaho): There are large amounts of potentially suitable habitat in the Lemhi and Salmon river valleys south of Salmon, Idaho, that do not contain Physaria didymocarpa var. lyrata. Most of this potential habitat is either BLM or private land. However, not all areas with potential habitat have been searched, especially where access is difficult, and along some private lands. New populations may continue to be periodically discovered, but most likely these will not be much outside the species presently known restricted range.
Craig, E. H. 1992. A study of population parameters and habitat characteristics of salmon twin bladderpod, Physaria didymocarpa var. lyrata. A Challenge Cost Share Project between USDI Bureau of Land Management, Salmon District Office and Western Ecological Studies Team. 23 pp.
Craig, E., and T. Craig. 1996. Population trends of Salmon River bladderpod, Physaria didymocarpa var. lyrata. 1991-1995. Challenge Cost-share project between the Bureau of Land Management and Western Ecological Studies Team. Bureau of Land Management, Salmon District Office, Salmon, ID. 24 pp.
Elzinga, C. 1990. Conservation Agreement for Physaria didymocarpa var. lyrata. Prepared for U. S. Fish and Wildlife Service, Endangered Species Program, and Bureau of Land Management, State Office.
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.
Moseley, R. K., M. Mancuso, and S. L. Caicco. 1990. Field investigations of two sensitive plant species on the Salmon National Forest: Phacelia lyallii and Physaria didymocarpa var. lyrata. Idaho Department of Fish and Game, Conservation Data Center, Boise. 17 pp. plus appendices.
Mulligan, G. A. 1968. Physaria didymocarpa, P. brassicoides, and P. floribunda (Cruciferae) and their close relatives. Canadian Journal of Botany 46: 735-740.
Rosentreter, R. 1982. The status report and recovery plan for the twin bladderpod flower in the Salmon District of the BLM. 27 pp.
U. S. Fish and Wildlife Service and Bureau of Land Management, Salmon District Office. 1984. Conservation Agreement for Physaria didymocarpa var. lyrata.
Author: M. Mancuso
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