Astragalus desereticus - Barneby
Deseret Milkvetch
Other Common Names: deseret milkvetch
Taxonomic Status: Accepted
Related ITIS Name(s): Astragalus desereticus Barneby (TSN 25490)
Unique Identifier: ELEMENT_GLOBAL.2.159222
Element Code: PDFAB0F2S0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Pea Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Fabales Fabaceae Astragalus
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Astragalus desereticus
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 30Mar2003
Global Status Last Changed: 29Nov1984
Rounded Global Status: G1 - Critically Imperiled
Reasons: A narrowly restricted endemic of Utah County, Utah with only one known site. The site is 0.93 km long by 0.31 km wide at its widest. Known from a single unprotected occurrence in occupied habitat of approximately 100 acres. There is little information available on population trends. Increased real estate development adjacent to the population poses a threat (direct construction impacts and subsequent increased recreational activities).
Nation: United States
National Status: N1

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Utah (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LT, PDL: Listed threatened, proposed for delisting (02Oct2017)
Comments on USESA: In the October 2, 2017 Federal Register, USFWS published a proposed rule to delist this species.  "This determination is based on a thorough review of all available information, which indicates that this species? population is much greater than was known at the time of listing in 1999 and that threats to this species have been sufficiently minimized."
U.S. Fish & Wildlife Service Lead Region: R6 - Rocky Mountain

NatureServe Global Conservation Status Factors

Range Extent Comments: ASTRAGALUS DESERETICUS is endemic to central Utah and known from only one occurrence in the Thistle Creek Valley near the town of Birdseye in Utah County. Occupied habitat is approximately 100 acres. It was first collected "below Indianola" on 2 June 1893 by Marcus E. Jones. Another collection, later designated by Barneby (1964) as the type specimen, was made on 17 June 1909 by Ivar Tidestrom on "slopes near Indianola." Despite numerous attempts to relocate the species (e.g., Barneby 1964), it remained obscure until its rediscovery on 28 May 1981 by Elizabeth Neese at its currently known location (Welsh and others 1987, Franklin 1990). The town of Indianola is actually in Sanpete County near the Utah County line, but whether the Jones and Tidestrom collections were made in Sanpete County is open to question. The Jones collection in particular is labeled "below" Indianola, presumably placing it downstream along the Thistle Creek drainage and therefore in Utah County (Franklin 1991). There are no recent collections or known occurrences of ASTRAGALUS DESERETICUS from Sanpete County, and it is likely that the two historical collections were made near the known location at Birdseye.

Number of Occurrences: 1 - 5
Number of Occurrences Comments: First collected in 1893 and later in 1909. Despite numerous attempts to relocate the species, it remained obscure until its rediscovery in May 1981. Currently known from a single population.

Population Size Comments: There is very little information available on population trends. Franklin (1990) estimated the population size at fewer than 5,000 plants. He noted that plants were most abundant toward the north end of the population, with individuals becoming widely scattered toward the south. During a subsequent visit, Stone (1992) observed that the northern part of the population appeared much the same, but that a high density of seedlings and young plants occurred locally in the southern portion of the Element Occurrence, indicating that the population had grown (at least in the short term) to more than 10,000 individuals.

Overall Threat Impact: High
Overall Threat Impact Comments: Increased real estate development is occurring adjacent to the species' only population and the strong potential exists for direct impact to the species from both construction and increased recreational activities (L. England, pers. comm.).

Roadside traffic is also a possible threat.

Many species of ASTRAGALUS in the Intermountain region are poisonous to livestock and therefore of concern to ranchers (Barneby 1989). However, there is no evidence of any past attempts to eradicate or control A. DESERETICUS for this reason.

With respect to potential grazing threats, Franklin (1990) noted that "[i]mpacts of grazing to the habitat, in the form of trails and trampling, are more apparent on the southern end of the [Birdseye] occurrence." However, in late May 1992 there were no signs of recent grazing in the occurrence area. Several animal trails traversed the middle slopes in the southern part of the site, but their use was evidently limited to deer.

Population biologists use the term demographic stochasticity to describe the effects of random events in the survival and reproductive success of individuals. Mathematical models suggest that demographic stochasticity is unlikely to cause extinctions unless the population becomes very small (i.e., on the order of 10s to 100s of individuals) as a result of other factors (Soule and Simberloff 1986, Shaffer 1987, Menges 1991). ASTRAGALUS DESERETICUS undoubtedly undergoes seasonal and annual fluctuations in population size (especially in response to environmental variables), but preliminary data on abundance trends indicate that demographic uncertainty alone is not a significant threat.

The random loss of genetic variability in a population is referred to as genetic stochasticity, a factor thought to have effects on both short-term viability and long-term adaptability to changing environmental conditions. There is now considerable empirical evidence to support the theory that rare plant species are often genetically impoverished (Karron 1987a, 1991). For example, the restricted ASTRAGALUS OSTERHOUTII and A. LINIFOLIUS exhibited lower levels of genetic polymorphism when compared with the widespread and closely related A. PECTINATUS (Karron 1988). Inbreeding depression (i.e., loss of fitness resulting from self-fertilization or breeding between close relatives) has been viewed as the principal threat to short-term viability in small populations (Shaffer 1987, Menges 1991), and for species that are normally outcrossing, a minimum effective population size of 50 individuals has been recommended to prevent harmful inbreeding effects (Franklin 1980, Soule 1980). Although inbreeding depression is likely to be less deleterious in plant populations, particularly for those species which have a history of inbreeding due to small neighborhood sizes (restricted gene flow) and specific adaptations for selfing, the phenomenon occurs even in some species that frequently self-fertilize (Barrett and Kohn 1991, Menges 1991). Evidence the rare A. LINIFOLIUS, a moderately autogamous species, in which seedlings produced by selfing had significantly reduced biomass when compared with those resulting from outcrossing (Karron 1989).

In addition to the short-term effects of inbreeding, loss of genetic variation through stochastic forces such as the founder effect (demographic bottlenecks) or genetic drift (random changes in gene frequency) may compromise the potential for continuing adaptation to environmental change. Ideally, a population should be large enough so that the loss from genetic drift is balanced by the input of new genetic variation from mutation (Soule and Simberloff 1986), but mathematical models have shown that an effective population on the order of 500 individuals can maintain nearly as much genetic variability as an indefinitely large population (Franklin 1980, Lande and Barrowclough 1987, Holsinger and Gottlieb 1991). The actual number of individuals necessary to provide an effective population of several hundred will range from the upper 100s to the 1,000s, perhaps rarely the 10,000s, the reason being that the size of a breeding population is rarely equal to the total population size (Shaffer 1987, Barrett and Kohn 1991). Genetic influences, however, are likely to be relatively unimportant because environmental uncertainty may require much larger population sizes to maintain long-term viability of isolated, unsubdivided populations (Shaffer 1987, Holsinger and Gottlieb 1991).

In summary, the known population of ASTRAGALUS DESERETICUS is probably too large for genetic stochasticity to be a significant threat to the maintenance of this species.

Environmental stochasticity refers to random (or at least unpredictable) changes over time in a population's operational environment, including physical habitat parameters and biotic interactions with herbivores, pollinators, parasites, and competitors. Natural catastrophes (such as fires, droughts, torrential rainstorms, overgrazing, and insect and disease outbreaks) represent an extreme form of environmental stochasticity, differing only in their high magnitude and low frequency. Currently accepted mathematical models indicate that, except in very small populations, environmental variation and natural catastrophes are the primary threats to rare species not already endangered by deterministic forces (Ewens and others 1987, Goodman 1987). The model results also demonstrate that in the face of environmental uncertainty there is no threshold population size above which the likelihood of extinction becomes greatly decreased. Furthermore, as environmental parameters fluctuate more widely, the risk of extinction is expected to increase, with catastrophes probably representing the worst-case scenario (Menges 1991). Population sizes needed to buffer the effects of environmental fluctuations and catastrophes are on the order of 1,000 to 1,000,000 (Shaffer 1987); the known population of ASTRAGALUS DESERETICUS is toward the lower end of this range.

Among potential threats to ASTRAGALUS DESERETICUS from the realm of environmental stochasticity, grazing by domestic livestock is the most amenable to management actions aimed at reducing the threat.

Short-term Trend Comments: To date there is very little information available on population trends over time. Franklin (1990) mapped the Birdseye occurrence in five distinct subpopulations and noted that plants of ASTRAGALUS DESERETICUS were most abundant toward the north end of the population, with individuals becoming widely scattered toward the south. He visually estimated the population size at fewer than 5,000 plants. During a subsequent visit to the site in late May 1992, the northern part of the population appeared much the same, but high densities of seedlings and young plants occurred locally in the southern portion, indicating that the population had grown (at least in the short term) to more than 10,000 individuals and providing strong evidence that a large ASTRAGALUS seed bank exists on the site.

Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.
Environmental Specificity Comments: Edaphically restricted to one isolated soil type derived from coarse conglomerate in an area of otherwise fine soils (L. England, pers. comm.)

Other NatureServe Conservation Status Information

Distribution
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Global Range: ASTRAGALUS DESERETICUS is endemic to central Utah and known from only one occurrence in the Thistle Creek Valley near the town of Birdseye in Utah County. Occupied habitat is approximately 100 acres. It was first collected "below Indianola" on 2 June 1893 by Marcus E. Jones. Another collection, later designated by Barneby (1964) as the type specimen, was made on 17 June 1909 by Ivar Tidestrom on "slopes near Indianola." Despite numerous attempts to relocate the species (e.g., Barneby 1964), it remained obscure until its rediscovery on 28 May 1981 by Elizabeth Neese at its currently known location (Welsh and others 1987, Franklin 1990). The town of Indianola is actually in Sanpete County near the Utah County line, but whether the Jones and Tidestrom collections were made in Sanpete County is open to question. The Jones collection in particular is labeled "below" Indianola, presumably placing it downstream along the Thistle Creek drainage and therefore in Utah County (Franklin 1991). There are no recent collections or known occurrences of ASTRAGALUS DESERETICUS from Sanpete County, and it is likely that the two historical collections were made near the known location at Birdseye.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
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U.S. & Canada State/Province Distribution
United States UT

Range Map
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U.S. Distribution by County Help
State County Name (FIPS Code)
UT Utah (49049)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
16 Spanish Fork (16020202)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A perennial herb with gray-silvery leaves, 4-15 cm long. Flower petals white to pinkish with evident lilac-colored keel-tips. In bloom late April to early June.
Technical Description: ASTRAGALUS DESERETICUS is a subacaulescent, tufted, perennial herb of the Fabaceae (Legume family), subfamily Papilionoideae. Its stems are 0-6 cm long and arise from a tough, woody taproot topped by a branched, superficial caudex. The foliage is uniformly strigulose-villosulous with dull whitish, ascending, basifixed hairs, giving the plants a silvery-gray appearance. The short internodes are often concealed by the stipules, which are free (not united opposite petiole), lanceovate in outline and more-or-less amplexicaul, membranous in texture, and 3.5-7 mm long. The alternate leaves are 4-12 cm long and pinnately 11- to 17- foliolate, the leaflets 2-14 mm long, 1.5-8 mm wide, elliptic or obovate and acute or shortacuminate, the terminal leaflet jointed to the rachis. The racemes are borne on peduncles 2- 5.5 cm long and are 5- to 10 flowered, the flowers 18-23 mm long and whitish suffused with pale pink-purple (especially the wings), the purple-tipped keel 12-13.5 mm long. The axis is 0.5-2.5 cm long in fruit, and the sessile or substipitate pods are firm, unilocular, up to 12 mm long, and held in a steeply ascending to erect fashion, the surface of the valves obscured by a vesture that is both shaggy hirsute and closely tomentose. The specific epithet refers to the State of Deseret (pronounced DEZeh-RET), the name given to the Utah territory by the Mormons in 1849 (Barneby 1964).
Diagnostic Characteristics: ASTRAGALUS is one of the largest and most complex genera of flowering plants, with about 1,500 species primarily of the Northern Hemisphere (Barneby 1989). ASTRAGALUS DESERETICUS has been assigned to section Argophylli, a group of 36 species of western North America, all xerophytic perennials (Barneby 1964). Among experts, however, there is some disagreement over whether it should be placed nearer to A. ARGOPHYLLUS of the subsection Argophylli (Barneby 1964, 1989) or to A. PURSHII of the closely related subsection Eriocarpi (Welsh and others 1987). A. DESERETICUS differs from the parapatric A. ARGOPHYLLUS var. MARTINII in that the pods are densely longhirsute and tomentulose (vs. strigulose to strigose, the vesture not concealing the surface of the valves), relatively small (10-12 mm vs. 13-32 mm long), and with fewer ovules (1416 vs. 25-44 in number).

Occurring sympatrically with A. DESERETICUS are the less closely related A. UTAHENSIS (foliage more closely silvery pubescent, flowers lavender, pods larger and densely shaggy villous with hairs 4-8 mm long) and A. CALYCOSUS (foliage more closely silvery-pubescent, leaflets smaller, pods with short appressed hairs).

Barneby (1989), who has seen only pressed specimens of A. DESERETICUS, erroneously observed that it "differs ... from all near relatives ... in the stiff peduncles which carry the ripe pods aloft in a ring around the central tuft of leaves." In fact, A. DESERETICUS in the wild resembles its closest congeners in having fruiting peduncles that are humistrate (spreading over the ground surface) due to the weight of the pods.

Reproduction Comments: ASTRAGALUS DESERETICUS is a short-lived perennial with no means of vegetative propagation, therefore, perpetuation of the species depends on successful sexual reproduction. The breeding system of ASTRAGALUS DESERETICUS presently is unknown.

The structure of the ASTRAGALUS flower indicates an adaptation to pollination primarily by large bees. Seed set in the rare ASTRAGALUS LINIFOLIUS is limited by low rates of pollinator visitation (Karron 1987b), suggesting that livestock grazing and other land management practices that reduce the size of pollinator populations may adversely affect reproductive success in A. DESERETICUS.

Pre-dispersal predation of ASTRAGALUS seeds by several types of insect larvae has been reported (Green and Bohart 1975). Preliminary field observations in late May 1992 indicate that seed predation occurs infrequently in A. DESERETICUS, but insect populations probably fluctuate from year to year in relation to climatic and other factors.

Seeds of ASTRAGALUS DESERETICUS evidently lay dormant over the winter and germinate in the spring when soil moisture and temperature conditions are optimal for germination and seedling establishment.

Ecology Comments: ASTRAGALUS DESERETICUS is a short-lived perennial with no means of vegetative propagation. Perpetuation of the species thus depends on successful sexual reproduction. The period of vegetative growth and reproductive activity begins after the annual snowmelt, usually by about mid-April (Swenson and others 1981). Flowering and seed set occur in May and June (Barneby 1989). The pods are deciduous at maturity, and while lying on the ground they dehisce at the apex to release the seeds. Even plants that are well established begin to lose many of their lower leaves as soil moisture becomes critical with the onset of hot, dry summer weather. As the current season's stems die back, either in response to late summer drought or cold weather in the fall, new vegetative buds are initiated at the caudex, just at soil level. Insulated by snow cover from rare episodes of severe cold, these buds generally survive the winter to emerge and elongate into new shoots the following spring.

Several widespread species of ASTRAGALUS (namely, A. CIBARIUS, A. UTAHENSIS, A. PECTINATUS, A. KENTROPHYTA var. TEGETARIUS, and A. MISER var. BLONGIFOLIUS) are highly self- incompatible and appear to be obligate outcrossers (Green and Bohart 1975; Karron 1987a, 1989; Geer and Tepedino 1993). The breeding system of ASTRAGALUS DESERETICUS presently is not known, but species with restricted ranges and few individuals are likely to be self compatible, according to evolutionary theory (Harper 1979; Karron 1989, 1991). Self- compatibility has been demonstrated for A. ROBBINSII var. JESUPII, an endemic of the Connecticut River banks in New Hampshire and Vermont (Thompson 1991); for two restricted ASTRAGALUS taxa from western Colorado, A. OSTERHOUTII and A. LINIFOLIUS (Karron 1987a, 1989); and for A. MONTII, a high elevation limestone endemic on the Wasatch Plateau of central Utah (Geer and Tepedino 1993). However, the rare A. TENNESSEENSIS and A. MONOENSIS (an eastern California endemic) are both obligate outcrossers (Baskin and others 1972, Sugden 1985). ASTRAGALUS TEGETARIOIDES and the newly described A. ANXIUS (both local endemics in the western Great Basin) are similarly incapable of setting seed without pollinators and are likely self-incompatible (Meinke and Kaye 1992).

The structure of the ASTRAGALUS flower, like that of other papilionaceous legumes, indicates an adaptation to pollination primarily by large bees, which land on the keel petals and "trip" the flower while pressing under the banner (also known as "standard") to reach a nectary located at the base of the ovary. Based on previous studies of both widespread and rare ASTRAGALUS species in the Great Basin and elsewhere (Baskin and others 1972, Green and Bohart 1975, Sugden 1985, Karron 1987b, Thompson 1991), the most frequent pollinators are bumblebees (BOMBUS spp.) and other polylectic bees (i.e., generalists capable of using a variety of floral resources). According to Karron (1987b), there are two possible explanations for the association between generalist pollinators and restricted ASTRAGALUS species: (1) pollinator specialization is unlikely to evolve or be maintained since a small plant population can only sustain a limited number of forager individuals; and (2) the rare ASTRAGALUS taxa speciated from widespread taxa that are themselves generalist pollinated.

Seed set in the rare ASTRAGALUS LINIFOLIUS is limited by low rates of pollinator visitation (Karron 1987b), suggesting that livestock grazing and other land management practices that reduce the size of pollinator populations may adversely affect reproductive success in A. DESERETICUS. Sugden (1985), studying pollination biology of the restricted A. MONOENSIS, noted that bumblebees (BOMBUS spp.) usually nest in abandoned rodent burrows and concluded that grazing may decrease the number of existing and potential nest sites by causing these burrows to collapse. Pesticides used in statewide programs to control grasshoppers and other insect herbivores may also be harmful to bee populations (Harper 1979, Senft 1990). Because bees have low fecundity, their populations may not recover for many years following such episodes (Karron 1987b).

Pre-dispersal predation of ASTRAGALUS seeds by several types of insect larvae has been reported (Green and Bohart 1975). High seed parasitism has also been noted in A. SCAPHOIDES, a local species of southwestern Montana and adjacent Idaho (Lesica 1987), and in the rare A. OSTERHOUTII (Karron 1989). Preliminary field observations in late May 1992 indicate that seed predation occurs infrequently in A. DESERETICUS, but insect populations probably fluctuate from year to year in relation to climatic and other factors.

Seeds of ASTRAGALUS DESERETICUS evidently lay dormant over the winter and germinate in the spring when soil moisture and temperature conditions are optimal for germination and seedling establishment. Many legume seeds possess a hard outer coat which prevents germination by inhibiting water absorption. Baskin and Quarterman (1969) planted untreated seeds of A. TENNESSEENSIS and found that very few had germinated after one year. Maximum seed germination was obtained only after: (1) mechanical scarification of both the impermeable outer seed coat and a tough inner seed coat; and (2) leaching of an inhibitory substance(s) from the embryo. Similar seed germination requirements have been reported for other ASTRAGALUS species, including A. LENTIGINOSUS var. MICANS (Pavlik 1987a) and A. LINIFOLIUS and A. LONCHOCARPUS (Karron 1989). Assuming that seed dormancy is well developed in A. DESERETICUS and a large seed bank exists at the Birdseye site, these factors would: (1) increase the effective size of the population; and (2) ensure continuation of the population (without immigration) if seed set or seedling establishment fails in any given year (Baskin and Quarterman 1969, Baskin and Baskin 1978).

ASTRAGALUS DESERETICUS undoubtedly depends on favorable weather and soil moisture conditions during the growing season, especially in the critical period of initial seedling establishment. Seedling mortality is probably high, and establishment may be completely unsuccessful in some years. Baskin and others (1972) reported that only 21.5 percent of wild A. TENNESSEENSIS seedlings survived their first summer due to soil moisture stress in their open, rocky habitat. They also found that established plants required several years to reach reproductive maturity, leading them to conclude that very few seedlings reach the adult stage. Another study (Pavlik 1987a) determined a 95 percent mortality rate for germinules of A. LENTIGINOSUS var. MICANS (a threatened dune endemic in eastern California), with anecdotal observations suggesting successful establishment on the order of once every 2 to 4 years. Seed dormancy was well developed in this taxon, and the half-life of established plants was 2.7 years, suggesting an adaptive strategy whereby high seedling mortality is offset by long-lived seeds and high adult survivorship.

Many species of ASTRAGALUS in the Intermountain region are poisonous to livestock (Barneby 1989). Some ASTRAGALI are primary selenophytes (i.e., species which concentrate the toxic element selenium in their tissues and return it to the soil in soluble form that can be taken up by preferred forage plants). Many others synthesize nitrotoxins to which cattle and sheep are particularly susceptible. In addition, a few species produce an alkaloid compound (known as locoine or swainsonine) causing the disease called "locoism" found primarily in horses. The lack of the characteristic "snakelike" odor in A. DESERETICUS and the absence of other primary selenophytes in the area of the Birdseye occurrence indicate that the species is not a selenium accumulator (M. Ralphs, pers. comm. 1992). A recent assay for swainsonine in seeds of A. DESERETICUS also yielded negative results (Ralphs 1993). Both A. ARGOPHYLLUS and A. PURSHII contain low levels of nitrotoxins (Williams and Barneby 1977), and A. DESERETICUS probably contains them also, based on its phylogenetic relationships (Ralphs 1993).

The apparent restriction of ASTRAGALUS DESERETICUS to a single locality raises the question of whether it is a relatively "new" species on the scale of geologic time or a relict population of an older species that was once more widely distributed. Barneby (1989) noted that "proliferation [of ASTRAGALUS] by adaptive radiation into arid and otherwise hostile microhabitats appears to be a relatively recent phenomenon that has not yet run its course. An ability to colonize new unstable habitats in progressively dry climates has hastened evolution of the genus and incidentally given rise to many sharply differentiated but geographically restricted genotypes." Thus, based on the pattern of speciation in the genus as a whole, A. DESERETICUS is most likely a localized neoendemic.

Many endemics in ASTRAGALUS are restricted to inhospitable substrate conditions or limited by the abundance or absence of some particular soil mineral such as selenium, gypsum, or lime (Barneby 1964). One wonders then if A. DESERETICUS is restricted to some confining ecological niche or whether it is for some reason unable (or perhaps has not had sufficient time) to expand into other areas of suitable habitat. The absence of primary selenophytes such as STANLEYA PINNATA, ASTRAGALUS BISULCATUS, and XYLORHIZA spp. from the area of the Birdseye occurrence indicates that seleniferous soils are not a factor. A nearby site (east side of U.S. Highway 89 about 1 mile south of Birdseye) with surface geology mapped as the Moroni Formation (Witkind and Weiss 1985) has soils that are "strongly calcareous" (Swenson and others 1981, p. 77). However, soil pH at the A. DESERETICUS site has not been tested. Franklin (1990; pers. comm. 1992) reports that A. DESERETICUS is apparently specific to the Moroni Formation and that soils on other outcrops in the vicinity are more clay-rich and not as sandy as those at the Birdseye site.

Upper slopes within the Birdseye occurrence are steep and dominated by outcrops of poorly consolidated bedrock. ASTRAGALUS DESERETICUS occurs very sparsely on these slopes, as the erosion rate generally exceeds the rate of soil formation and there is little available rooting substrate. Middle slopes are moderately steep and have a thin mantle of loose, sandy soil overlying the parent material. ASTRAGALUS is more abundant in this topographic position, but erosion rates are high, creating an element of habitat instability which appears to limit the size (and probably the life span) of individual plants. Lower slopes (i.e., those closest to the highway) are more gradual and also more stable, with deeper soils. Here A. DESERETICUS cover is at its maximum, and the plants are generally much larger (and probably longer-lived) than on midslopes. Large and vigorous plants are also found on the adjoining west-facing road cuts above the highway.

Intolerance of shade is very common in the genus ASTRAGALUS (Barneby 1964), and A. DESERETICUS is seemingly excluded from the denser pinyon-juniper tracts characteristic of slopes in the vicinity of the Birdseye site. Within its area of occurrence the species is only rarely found on north-facing exposures (Franklin 1990). However, there appears to be little likelihood that the Birdseye population would ever decline significantly via competitive exclusion by the woodland dominants, since its habitat exists in a state of "perpetual succession" due to high soil erosion rates on steep slopes.

Terrestrial Habitat(s): Forest/Woodland, Savanna, Shrubland/chaparral, Woodland - Conifer
Habitat Comments: SUMMARY: Within juniper-sagebrush communities on open, steep, naturally disturbed south and west (rarely north) facing slopes of sandy-gravelly soils of the Moroni Formation. Grows well on immediately adjacent, west-facing road cuts, where the plants are typically larger. 1645-1740 m elevation. END SUMMARY

The "Birdseye occurrence" is mapped by Franklin (1990) on steep, south- and west-facing slopes east of the town, covering 100 acres on the east side of U.S. Highway 89. Elevations at this site range from 1645-1740 meters (5400 to 5700 feet).

Located east of Mt. Nebo (southern Wasatch Range) at the western base of the Manti Mountains (northern end of the Wasatch Plateau), the area has a dry subhumid climate with an average annual precipitation of 13 inches (Swenson and others 1981). Precipitation during the period October through April is associated with eastward-moving Pacific storms and is rather uniform at about 1.2 inches per month. Snowfall (which averages 65 inches per year at Birdseye) accounts for most of this winter precipitation. May through September is slightly drier, with rainfall averaging about 0.9 inches per month and mainly the result of thunderstorms forming in warm, moist air from the Gulf of Mexico. The mean annual air temperature is 42 F, and the frost-free period is about 80 to 120 days. Winters are cold but not severe, and summers are very mild with maximum daily temperatures generally in the 80's.

The area of the Birdseye occurrence is mapped as "Rock Land" (Swenson and others 1981), comprising outcrops of the Moroni Formation along with the residual and colluvial soils weathered from them. The Moroni Formation, which consists of pyroclastic rocks and associated sediments of Oligocene age (36.6 to 23.7 million years before present), is limited to an area of about 100 mi?, primarily on the eastern slopes of the southern Wasatch Range and the Cedar Hills between Thistle and Moroni. Outcrops vary in composition but include tuff, breccia, and conglomerate of volcanic origin along with sandstone and siltstone (some highly calcareous) and water- laid conglomerate (Phillips 1962, Stokes 1986). In the vicinity of the Birdseye occurrence, the Moroni Formation is made up of "[c]onglomerate beds [that] are crudely bedded and commonly poorly sorted, and [that] contain volcanic cobbles and pebbles, and well-rounded clasts of tan quartzite, dark- blue limestone, and sandstone...." (Witkind and Weiss 1985). Soils derived from this particular exposure of the Moroni Formation are stony sandy loams.

Vegetation at the site can be described as an open to sparse woodland of two-needle pinyon (PINUS EDULIS) and Utah juniper (JUNIPERUS OSTEOSPERMA). Other woody plants growing in association with ASTRAGALUS DESERETICUS are QUERCUS GAMBELII, ARTEMISIA TRIDENTATA, and PURSHIA TRIDENTATA. Associated grasses and forbs include ELYMUS SPICATUS, STIPA HYMENOIDES, S. COMATA, ERIOGONUM BREVICAULE, and PENSTEMON SCARIOSUS. Nonirrigated, upland sites in the Birdseye vicinity are generally used as spring and fall range by cattle or sheep and as winter range by mule deer and elk (Swenson and others 1981).

Economic Attributes
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Economically Important Genus: Y
Management Summary
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Stewardship Overview: ASTRAGALUS DESERETICUS is a very scarce plant known from only one location in central Utah. Primary management concerns for ASTRAGALUS DESERETICUS center on protecting this one location from degradation by anthropogenic and (insofar as possible) "natural" sources.

Stewardship priorities for ASTRAGALUS DESERETICUS are as follows:

1. Protect the Birdseye occurrence by completing private land sales and negotiating a management agreement with the Utah Division of Wildlife Resources.

2. Initiate demographic monitoring to assess population trends and evaluate impacts from grazing and other environmental factors.

3. Conduct field searches to locate additional natural populations and to identify areas of suitable but unoccupied habitat for possible recovery efforts.

4. Consider fencing the perimeter of the Birdseye occurrence after population trends and grazing impacts have been fully evaluated.

Species Impacts: ASTRAGALUS DESERETICUS is a member of the native flora of Utah. It is not a pest or weed, and has no known adverse effects on its associated species or surrounding environment.
Restoration Potential: The Birdseye occurrence of ASTRAGALUS DESERETICUS can be looked upon as an "island" in a "sea" of unsuitable habitat. In other words, there appears to be no potential for the species to expand its distribution into immediately surrounding areas. It is difficult to suggest what potential may exist for increasing the density of the Birdseye population without hard data on population trends. In general, however, we can expect that the current population size is more or-less in equilibrium with the frequency and magnitude of natural disturbance on the site. The technology already exists to propagate and maintain ASTRAGALUS species indefinitely in cultivation (see Baskin and Quarterman 1969, Karron 1989), but it is unlikely that new populations can be established in the wild until additional areas of suitable habitat are located.
Preserve Selection & Design Considerations: The land occupied by ASTRAGALUS DESERETICUS is owned by the Utah Division of Wildlife Resources (DWR) and two private land owners. The site is located in a rural, unincorporated area and is undeveloped except for a barbed wire fence bordering the highway and a small cabin located adjacent to the highway on one of the private parcels. Existing zoning regulations effectively limit development to agricultural and low-density residential uses. In addition, livestock grazing is considered an uneconomical use of the two private parcels because of their small size and generally steep slopes (Hales 1991).

The DWR land is a wildlife management area which is also used for cattle grazing, and part of the area immediately east and upslope of the ASTRAGALUS occurrence has been chained and seeded for range improvement. Cattle grazing reportedly occurs within the DWR management area about once every three years, but there was no grazing on the site in 1991 or 1992 (J. Fairchild, pers. comm. 1992). The DWR is not a party to any long-term leases, and light to moderate grazing is applied on an as-needed basis to promote browse production on big-game winter range. Typically, 50 head of cattle are allowed to graze the site for one month, from mid-May to mid-June (precisely within the period of flowering, seed set, and early seedling establishment in ASTRAGALUS DESERETICUS). Although there are no fences separating the DWR and adjacent private lands (Franklin 1990), cattle tend to concentrate upslope in the chained-and-seeded area where forage production is higher (J. Fairchild, pers. comm. 1992).

The habitat of ASTRAGALUS DESERETICUS exists in a state of "perpetual succession" due to high soil erosion rates on steep slopes. Upper slopes within the Birdseye occurrence are steep and dominated by outcrops of poorly consolidated bedrock. ASTRAGALUS DESERETICUS occurs very sparsely on these slopes, as the erosion rate generally exceeds the rate of soil formation and there is little available rooting substrate. Middle slopes are moderately steep and have a thin mantle of loose, sandy soil overlying the parent material. ASTRAGALUS is more abundant in this topographic position, but erosion rates are high, creating an element of habitat instability which appears to limit the size (and probably the life span) of individual plants. Lower slopes (i.e., those closest to the highway) are more gradual and also more stable, with deeper soils. Here A. DESERETICUS cover is at its maximum, and the plants are generally much larger (and probably longer-lived) than on midslopes. Large and vigorous plants are also found on the adjoining west-facing road cuts above the highway.

Intolerance of shade is very common in the genus ASTRAGALUS (Barneby 1964), and A. DESERETICUS is seemingly excluded from the denser pinyon-juniper tracts characteristic of slopes in the vicinity of the Birdseye site. Within its area of occurrence the species is only rarely found on north-facing exposures (Franklin 1990).

Management Requirements: The primary conservation objective for ASTRAGALUS DESERETICUS should be to protect and manage the Birdseye occurrence (i.e., the only known population and its essential habitat). To date, the Utah Field Office (UTFO) has initiated a project to acquire the purchasable habitat from two cooperative landowners. Following an appraisal (Hales 1991), the UTFO obtained one option. More recently, DWR has requested information on the distribution and abundance of ASTRAGALUS DESERETICUS for use in ongoing management of their lands (J. Fairchild, pers. comm. 1992). Protection efforts at the Birdseye occurrence should continue through completion of private land sales and negotiation of a management agreement with DWR.

Attempts to locate additional populations of ASTRAGALUS DESERETICUS, both in the vicinity of the Birdseye occurrence and on the nearby Manti-La Sal National Forest, have thus far met with no success (Franklin 1990). Until such time as additional populations (or areas of suitable but unoccupied habitat) are found, no other land acquisition or protection actions are warranted.

The habitat of ASTRAGALUS DESERETICUS exists in a state of "perpetual succession" due to high soil erosion rates on steep slopes. Thus there is no need for active management to reduce interspecific competition or to maintain the site in an early successional stage. In addition, the population is not currently subject to any anthropogenic disturbances requiring immediate correction or control. Since environmental variation is the primary threat to rare species not already endangered by deterministic factors, the main objective of any management program for A. DESERETICUS would be to reduce its exposure to environmental variation, if possible.

The main issue that needs to be resolved vis-(-vis future management of ASTRAGALUS DESERETICUS is whether the site should be fenced. Experience at the nearby Soldier Summit Preserve, established for an endangered plant (PHACELIA ARGILLACEA) which has clearly suffered from tremendous grazing pressures, has shown that fencing the site's perimeter can eliminate large herbivores and lagomorphs entirely (Callister and Van Pelt 1990). However, construction of a similar fence on the steep ground of the Birdseye occurrence would be costly and would entail a commitment to continuing maintenance. In addition, fencing may not be justified considering the current grazing regime and steep, unstable slopes which form a natural barrier, helping to limit access to the site by cattle. In view of these facts, the decision to fence the site should be delayed until a more detailed assessment of population trends and grazing impacts is completed.

Monitoring Requirements: A monitoring program should be initiated at the Birdseye occurrence to assess population trends over time, gain an understanding of critical life-history attributes, and evaluate impacts from grazing and other environmental factors.

Monitoring data should be collected in a series of permanent plots. One such plot has already been placed in the Birdseye population (see description in the MONIT.PROG field below). Additional plots of a similar configuration should be located in other parts of the occurrence area (i.e., on upper, middle, and lower slopes and toward the northern and southern ends of the population) to account for spatial variability in demographic parameters. Alternatively, a series of permanent belt transects could be used, as described by Lesica (1987).

Within each 1 m quadrat, individual ASTRAGALUS DESERETICUS plants should be classified as to size class (germinule, seedling, juvenile, or adult) and precisely mapped using a Cartesian coordinate system. This will allow the reproductive output and fate of individual plants to be tracked over time. Additional data to be collected for each plant might include rosette diameter, distance to nearest adult, number of inflorescences, number of flowers per inflorescence, number of pods per inflorescence, and indexes of herbivory, trampling, and pre- dispersal seed predation. This protocol should be followed twice each year (once in late spring and again in late summer) to collect information on seedling survivorship over the hot, dry summer season. The number of flowers per inflorescence can be estimated even when the plants are in fruit by counting the number of visible pedicel scars and adding that to the number of pods per inflorescence (Karron 1989).

The number of seeds per pod and the ovule-to-seed ratio are also of interest since they may yield information on fecundity and breeding system. These parameters can be determined by carefully opening and examining a small, random sample of pods (i.e., 5 to 10 pods per plot). Unfertilized ovules in ASTRAGALUS (as in several other legume species) do not disintegrate and are readily counted in mature fruits (Karron 1989). Survivorship and seed production data are potentially useful in estimating the net reproductive rate (i.e., whether the population is growing or declining), but problems arise in determining survivorship within seed cohorts between dispersal and germination. Nevertheless, population trends and management practices can still be evaluated by comparing halflives (i.e., the time required for half of the individuals in a cohort to die), survivorship at reproductive maturity, and year-to-year variation in reproductive output (Pavlik 1987b).

A minimum of two years of monitoring data under similar environmental conditions are needed to establish a population trend. However, the resulting estimate is only as reliable as the environmental parameters during that time period are representative of the future (Menges 1986). In other words, a long-term monitoring program is essential for determining how population trends are influenced by such factors as erosional events (torrential rainstorms), successive drought years, livestock grazing (which reportedly occurs in the area only once every several years), and fluctuations in rates of pollinator effectiveness and seed predation. It is recommended that initial funding should be sought for five years of demographic monitoring, with the option to continue based on an evaluation of the representativeness of the data set.


Management Programs: There are no active management programs currently underway.
Monitoring Programs: One permanent monitoring plot was subjectively established in May 1992 at a mid-slope location near the southern end of the Birdseye occurrence. Sections of iron rebar were driven into the ground at 10-meter intervals and flagged to mark the corners of a square. A meter tape was then extended around the perimeter of the plot, and pin flagging was placed at every meter mark along the tape. Finally, lengths of cotton twine were extended from the pin flags across the plot to form a grid of 1 m sections.

Several possibilities exist for obtaining the necessary technical expertise and funding to implement the ASTRAGALUS DESERETICUS monitoring program. First, it could be accomplished using resources available to the Utah Field Office or through cooperation with the Utah Natural Heritage Program in Salt Lake City. Second, the project could be completed by a local academic institution (e.g., University of Utah, Utah State University, Brigham Young University), either by a faculty member or a graduate student under faculty guidance. A third source of cooperative funding might be the U.S. Fish and Wildlife Service (USFWS), since that agency may soon be proceeding with a listing proposal for A. DESERETICUS under the Endangered Species Act (L. England, pers. comm. 1997). If ASTRAGALUS DESERETICUS becomes Federally listed as Endangered or Threatened, a special permit from the USFWS may be needed before proceeding with certain aspects of the monitoring program (such as collection of data on seed production).

Management Research Programs: There are no active research programs currently underway for ASTRAGALUS DESERETICUS.
Population/Occurrence Delineation
Help
Minimum Criteria for an Occurrence: A natural occurrence of one or more plants.
Separation Barriers: EOs are separated by either: 1 kilometer or more across unsuitable habitat or altered and unsuitable areas; or 2 kilometers or more across apparently suitable habitat not known to be occupied.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 2 km
Separation Justification: The rationale for this large a separation distance across suitable but apparently unoccupied habitat is that it is likely additional research will find this habitat to be occupied. It can often be assumed that apparently unconnected occurrences will eventually be found to be more closely connected. No information on mobility of pollen and propagules is available on which to base the separation distance for this species.
Date: 04Mar2002
Author: Ben Franklin
Population/Occurrence Viability
Help
Excellent Viability: SIZE: 1000 or more individuals (based on available EO data). CONDITION: The occurrence has an excellent likelihood of long-term viability as evidenced by the presence of multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. This occurrence should be in a high-quality site with less than 1% cover of exotic plant species and/or no significant anthropogenic disturbance. LANDSCAPE CONTEXT: The occurrence is surrounded by an area that is unfragmented and includes the ecological processes needed to sustain this species. This includes the presence of very specific edaphic requirements in a matrix of pinyon-juniper woodlands. This species is known to grow exclusively on the sandy-gravelly soils that are weathered from the "conglomerate beds" of the Moroni Formation (Franklin 1990).
Good Viability: SIZE: 100 to 999 individuals (based on available EO data). CONDITION: 100 to 999 individuals (based on available EO data). LANDSCAPE CONTEXT: The occurrence should have a good likelihood of long-term viability as evidenced by the presence of multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. Anthropogenic disturbance within the occurrence is minimal. If exotic species are present, they comprise less than 10% of the total ground cover.
Fair Viability: SIZE: The surrounding landscape should contain the ecological processes needed to sustain the occurrence but may be fragmented and/or impacted by humans. CONDITION: 20 to 99 individuals (based on available EO data). LANDSCAPE CONTEXT: The occurrence may be less productive than the above situations, but is still viable, with multiple age classes and evidence of flowering and fruiting, indicating that the reproductive mechanisms are intact. The occupied habitat is somewhat degraded (exotic plant species make up between 10-50% of the total ground cover and/or there is a moderate level of anthropogenic disturbance).
Poor Viability: SIZE: There may be significant human disturbance, but the ecological processes needed to sustain the species are still intact. CONDITION: Less than 20 individuals (based on available EO data). LANDSCAPE CONTEXT: Little or no evidence of successful reproduction is observed (poor seedling recruitment, no flowering or fruiting observed, or poor age class distribution). Exotic plant species make up greater than 50% of the total ground cover, and/or there is a significant level of human disturbance.
Justification: SIZE: Large populations in high quality sites are presumed to contain a high degree of genetic variability, to have a low susceptibility to the effects of inbreeding depression, and to be relatively resilient. EOs not meeting "C"-rank criteria are likely to have a very high probability of inbreeding depression and extirpation due to natural stochastic processes and/or occur in degraded habitat with low long-term potential for survival. CONDITION: Large populations in high quality sites are presumed to contain a high degree of genetic variability, to have a low susceptibility to the effects of inbreeding depression, and to be relatively resilient. EOs not meeting "C"-rank criteria are likely to have a very high probability of inbreeding depression and extirpation due to natural stochastic processes and/or occur in degraded habitat with low long-term potential for survival. LANDSCAPE CONTEXT: Large populations in high quality sites are presumed to contain a high degree of genetic variability, to have a low susceptibility to the effects of inbreeding depression, and to be relatively resilient. EOs not meeting "C"-rank criteria are likely to have a very high probability of inbreeding depression and extirpation due to natural stochastic processes and/or occur in degraded habitat with low long-term potential for survival.
Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 27Feb1997
NatureServe Conservation Status Factors Author: D. Stone, rev. B. Franklin (1996 and Sept/97).
Management Information Edition Date: 27Feb1997
Management Information Edition Author: R. DOUGLAS STONE
Management Information Acknowledgments: This Element Stewardship Abstract has been reviewed by Jeff Baumgartner (TNC Western Regional Office), 92-10-09 memo; and David A. Pyke (BLM Cooperative Research Unit, Corvallis OR), 93-04-20 letter. In addition, an assay for swainsonine (a toxic alkaloid in ASTRAGALUS species) was performed by Michael H. Ralphs (USDA Poisonous Plant Research Laboratory, Logan UT), with results reported in a letter dated 93-06-29. Earlier versions of this Element Stewardship Abstract, all written by R. Douglas Stone, were dated 92-08-24, 92-12-04, and 94-11-21.

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

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