CPC National Collection Plant Profile

Astragalus applegatei

Photographer:
Kagan/Yamamoto

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CPC National Collection Plant Profile

Astragalus applegatei


Family: 
Fabaceae  
Common Names: 
Applegate's milkvetch, Applegate's milk-vetch
Author: 
M.E. Peck
Growth Habit: 
Forb/herb
CPC Number: 
368

Distribution
Protection
Conservation
References


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Astragalus applegateienlarge
Photographer: Kagan/Yamamoto

Astragalus applegateienlarge
Image Owner: The Nature Conservancy


Astragalus applegatei is Not Sponsored
Primary custodian for this plant in the CPC National Collection of Endangered Plants is: 
Edward Guerrant, Ph.D. contributed to this Plant Profile.

 
Astragalus applegatei


In the mid-1980s, a significant portion of the largest remaining Applegate's milkvetch population was paved over to make way for an auto dealership and grocery store. Since the site, which was just outside Klamath Falls, Oregon, contained the largest remaining population, this destruction was especially detrimental to the future of this species. Even before this unfortunate event, however, Applegate's milkvetch had reached a critical point. Land development, noxious weed introduction, and the suppression of fires within its limited range had dramatically reduced suitable habitat. Consequently, Applegate's milkvetch is only found at three sites. Of the approximately 12,000 individuals that remain, nearly all are found at the one location outside of Klamath Falls.

While conservation efforts are underway, Applegate's milkvetch is still severely threatened. The Nature Conservancy purchased a portion of the land that contains the vital Klamath Falls population, but the remaining area is still at risk of development. Alarmingly, this protected population has decreased to fewer than 8,000 individuals. The other two locations are on public lands and are protected by its listing as Endangered by the Fish and Wildlife Service. Nevertheless, these two sites contain very few individuals, only 500 and 3, respectively. Due to these small population sizes, persistence is uncertain as these sites are especially susceptible to random disturbance and the lack of genetic variation may cause problems associated with inbreeding.

Applegate's milkvetch is distinguishable in mid-summer by its small, whitish flowers with purple tips. This plant is also unique because it is only found in flat, seasonally moist meadows and flood plains of the Lower Klamath Basin. The US Fish and Wildlife Service has developed a recovery plan that aims to increase the number of plants to six populations with a minimum of 4,500 plants each. At that point, Applegate's milkvetch will be considered for downlisting to threatened status.

Distribution & Occurrence

State Range
  Oregon
State Range of  Astragalus applegatei
Habitat
  • Flat, open, seasonally moist remnants of floodplain alkaline grassland of the Klamath Basin (Williams and Parenti 1991, USFWS 1997).
• Habitat was historically characterized by sparse, native bunch grass and patches of bare soil (USFWS 1997).
• Elevation 4,100 ft (1250 m).

Distribution
  Oregon, East Cascades geographic province- Presently only found at three locations all within the lower Klamath Basin. A fourth population existed about 10 miles SW of Klamath Falls, indicating this species was once more widespread. It is probable that Applegate's milkvetch once occurred along fringes of the marshes and floodplain of Upper Klamath Lake and Ewauna Lake, and likely other areas throughout pre-settlement Lower Klamath Basin (USFWS 1997).

Number Left
  As of 1998: 3 populations:
• One with 11,500 individuals (seven acres with the greatest number and density of plants is owned and managed by The Nature Conservancy, while the remainder is on private land).
• Another with fewer than 500 individuals (owned and managed by the Oregon Department of Fish and Wildlife).
• A third with only 3 plants (discovered in 1997) (USFWS 1998).

Protection

Global Rank:  
G1
 
8/23/2000
Guide to Global Ranks
Federal Status:  
LE
 
7/28/1993
Guide to Federal Status
Recovery Plan:  
Yes
 
4/10/1998

State/Area Protection
  State/Area Rank Status Date  
  Oregon S1 LE 10/27/1989  

Conservation, Ecology & Research

Ecological Relationships
  Astragalus applegatei is unable to colonize dry, disturbed areas (USFWS 1997). Seasonal flooding may be important in providing openings for establishment and in limiting the dominance of other species (USFWS 1997). The decline observed at the site managed by The Nature Conservancy in recent years is likely due to quackgrass (Elytrigia (Agropyron) repens) colonization and past hydrologic alterations that appear to have converted open prairie to a more densely covered meadow. These changes may be responsible for decreased rates of germination and seedling survival. It is important to note, however, that while the quackgrass colonization appears to be increasing, the A. applegatei population appears to be stabilizing (Borgias 2001).

The above ground portion of Astragalus applegatei dies back completely after flowering, then in the fall re-sprouts short (0.5-2 inch) stems bearing immature leaves. Reproduction is achieved exclusively by seeds. Bumblebees, butterflies and polylectic bees are the most likely pollinators (Gisler and Minke 1998 and USFWS 1998). Autogamy (self-pollination) is common in the Astragalus genus and is facilitated by simultaneous ripening of anthers and stigmas (Barneby 1964 in Gisler and Meinke 1998). Astragalus applegatei seeds that are produced by self-fertilization do not appear to have lower viability than those produced by outcrossing (Gisler and Meinke 1998). It is likely that autogamy is a vital life-history strategy for rare, locally endemic flora that might otherwise be especially vulnerable to inconsistent pollinators (Karron 1987 and Greer et al. 1995 in Gisler and Meinke 1998).

Flowering occurs in early June through August. Seeds show no specialized mechanisms for long distance dispersal. Species may have historically existed on bare patches of soil, possibly allowing for wind movement of seeds along soil surface. Present day dense coverage by introduced grasses and weeds likely reduces this wind caused movement (USFWS 1998).

Even though each fruit typically contains 8-10 ovules, production of greater than 3 (if any) seeds per pod is rare (USFWS 1997). Flowers attract a large variety of bees and other insects and equally low seed set has been documented among individuals grown under presumably optimum greenhouse conditions. It is therefore suspected that low seed set is due to genetic constraints as opposed to resource and/or pollinator limitations (Gisler and Meinke, 1998).

Difficulties with cultivation using conventional propagation techniques suggests that A. applegatei may have evolved a complex reliance on particular soil ecosystem properties (Gisler and Meinke 1998). Results from a soil symbiont study indicate that there may be a certain degree of specificity. Specificity between host and symbionts is generally thought to be uncommon, but in a recent study there was no evidence of symbiont root colonization with commercial mixtures of Rhizobium bacteria and VAM fungi. It is possible that the commercial inoculums contained nonviable propagules. Regardless of viability, this study showed the value of simply using field soils inoculums and has important restoration implications (Geisler and Meinke 1998).

In a recent study, Astragalus applegatei grown in native soil treated with fungicide were far less vigorous than in the untreated native soil, but performed better than when grown in soil inoculated with a commercial soil inoculum. Since the fungicide selectively removed VAM fungi, leaving Rhizobium to colonize in its absence, these results suggest that VAM fungi provide the majority of symbiont benefits. However, there may be a synergistic relationship between VAM fungi and Rhizobium, and the relative benefits from VAM fungi and Rhizobium cannot be definitively concluded (Gisler and Meinke 2001). Additional research on this subject is being conducted.

Threats
  • Habitat conversion to fields and pasture (Meinke 1982 & USFWS, 1998).
• Commercial development on habitat of largest (and only genetically viable) population. Negotiations to lease the land from the owner were unsuccessful. The area is now an auto dealership and warehouse grocery store. Additional portions of this population occur on private lands currently posted for sale as industrial lots (U.S. Fish and Wildlife Service 1998).
• Low population numbers. Low seed set. Little soil seed banking (Recovery Plan). (USFWS 1998).
• Cattle grazing (USFWS 1998).
• Colonization by Quackgrass and the conversion from open alkali prairie to a more densely covered meadow, thereby causing decreased seed germination and decreased seedling survival (Borgias 2001)
• Invasion of exotics species leading to increased leaf litter, increased nitrogen fixation by introduced legumes, and ultimately secondary succession by shrubs and other herbaceous species (USFWS 1997).
• Alteration of local hydrology and a lack of seasonal flooding due to extensive construction of drainage ditches and dikes throughout Lower Klamath Basin (USFWS 1998).
• Herbivory (especially by the Plebejus melissa caterpillar) (Gisler and Meinke 1998) and seed predation by adult and larval beetles (USFWS 1998).

Current Research Summary
  • Low seed sets among irrigated, fertilized, greenhouse-grown, and hand-pollinated plants suggest that low seed set is not a result of water or macronutrient deficiency, but rather may be limited by intrinsic genetic factors, possibly inbreeding depression, or other resource limitations (USFWS 1997).
• Greenhouse experiments revealed that native soil inoculation was successful at facilitating abundant colonization of mycorrhizal fungi. Plants were grown in both non-inoculated and inoculated soil, and only those plants from the inoculation treatment survived (Barroetavena et al. 1998).
• Growth and survival of individuals grown under greenhouse conditions in six experimental soil treatments were compared: 1) field soil from natural habitat, 2) field soil subjected to heat sterilization (control treatment), 3) field soil treated with fungicide, 4) commercial grade Rhizobium inoculum, 5) commercial grade mycorrhizal (VAM) inoculum, and 6) mixture of commercial grade Rhizobium + VAM inoculate. Plants were not fertilized. Results from the trials clearly indicate that A. applegatei grew best under the field soil treatment. Astragalus applegatei grown under the field soil treated with fungicide treatment performed slightly better than the control and commercial inoculum treatment, but not nearly as well as the untreated field soil treatment (Gisler and Meinke 2001).
• Growth and survival of individuals grown with sterilized soil inoculated with a small amount of field soil were compared. Only one tablespoon of field soil was needed to promote healthy growth for each individual, posing little threat of depleting natural populations of their soil. Alternatively, a self-sustainable source of inoculum can be developed from a field soil inoculum starter in the greenhouse using other species of host plants (Gisler and Meinke 2001).
• Germination trials at The Berry Botanic Garden. For scarified seeds, all treatments (Either 8 weeks cold stratification or no cold stratification and either constant 68°F (20°C) or alternating 50°/68°F (10/20° C) treatments yielded between 40 and 60 % germination (BBG File).

Current Management Summary
  • Protection from grazing, vehicular traffic, development on site managed by Oregon Department of Fish and Wildlife (USFWS 1997).
• Grazing does occur at the Klamath Wildlife Area (Gisler and Meinke 1998).
• Experimental prescribed burning, herbicide application, and mowing at site managed by The Nature Conservancy to examine the influence of invasive species on Astragalus applegatei populations (USFWS 1997)
• Recovery plan finalized in 1998.
• 1,500 individuals were cultivated for introduction to the Klamath Wildlife Area. Seeds were collected from the Klamath Wildlife Area population being augmented. Despite consistently high (~ 90%) germination rates after scarification, the fungal root pathogen Fusarium oxysporum stunted growth and greatly reduced the number of plants available for outplanting. Fungicide, fertilization, and irrigation treatment failed to decrease infection. In all cases, only 12 and 14% of plants were usable, and even those plants available for outplanting were of questionable vigor. Of these plants, few survived one growing season (Gisler and Meinke 1998).
• Monitoring at the site managed by The Nature Conservancy. At this site, recruitment is decreasing and seedlings have become rare within the macroplots that were established in 1988 for long term monitoring. This population initially showed an increase from 1988 to 1991, when it hit a high at nearly 30,000 estimated individuals. Since 1995, the population has been hovering at lowest record levels of abundance (between ~4,500 to ~10,000 individuals). Though poorly documented, distribution of Astragalus applegatei individuals outside the macroplot suggests that the population may be expanding westward. It is important to note that the suitability of habitat is this new area is questionable, and that slow dispersal rate may limit the extent of colonization (Borgias 2001).
• Seed from one population is stored at The Berry Botanic Garden.

Research Management Needs
  • Study levels of seedling recruitment, natural rates of plant development, plant longevity, and minimum population sizes required for long term survival (USFWS 1997).
• Study outcrossing rates, and relative fitness between individuals resulting from self- and cross-pollinated seeds (USFWS 1997).
• Research impacts of competition from weeds and other plants. Explore whether the presence of other plants facilitate pollination by attracting pollinators or reduces pollination due to competition for pollinators (USFWS 1997).
• Investigate the benefits of controlled burning (USFWS 1997).
• Determine alkalinity tolerance, and to what degree soil specialization may prevent competitive exclusion by other less alkaline-tolerant native taxa (USFWS 1997).
• Study salinity and hydrological tolerances (Borgias 2001).
• Identify the abundance and geographic distribution of soil symbionts. In habitats lacking such symbionts, it may be possible to inoculate sites with field soil from natural populations to increase potential habitat for A. applegatei (Gisler and Meinke 2001).
• Further research on the extent, impacts, and possible control of herbivory and predation (USFWS 1997).
• Study age structure and levels of recruitment population dynamics in order to assess the long-term viability of population in terms of age/growth stage structure (USFWS 1997).
• Monitor the westward expansion of A. applegatei at the site managed by The Nature Conservancy (TNC) population (Borgias 2001).
• Determine the long term effect of quackgrass colonization on the TNC Astragalus applegatei population (Borgias 2001).
• Investigate whether appropriate soil microfauna in field soil samples can survive dry frozen storage.

Ex Situ Needs
  • Collect and store seed from all known populations. Collect a few seeds over a period of years to reduce the impact of seed removal on the population.
• If techniques can be developed, collect and store field soil samples containing appropriate soil microflora to aid in population establishment or reintroduction.

References

Books (Single Authors)

Abrams, L.; Ferris, R.S. 1944. Illustrated Flora of the Pacific States: Washington, Oregon, and California. Stanford, CA: Stanford University Press.

Barneby, R.C. 1964. Atlas of North American Astragalus. Bronx, New York: New York Botanical Garden. 1188p.

Eastman, D.C. 1990. Rare and Endangered Plants of Oregon. Beautiful America Publishing Company. 194p.

Isely, D. 1998. Native and Naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Salt Lake City, Utah: Monte L. Bean Life Science Museum, Brigham Young University.

Meinke, R.J. 1982. Threatened and Endangered Vascular Plants of Oregon: An Illustrated Guide. Portland, Oregon: U.S. Fish & Wildlife Service, Region 1. 326p.

ONHP. 2001. Rare, Threatened and Endangered Plants and Animals of Oregon.

Books (Sections)

Kartesz, J.T. 1999. A synonymized checklist of the vascular flora of the U.S., Canada, and Greenland. In: Kartesz, J.T.; Meacham, C.A., editors. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden. Chapel Hill, NC.

Liston, A. 1997. The genus Astragalus (Fabaceae) in Oregon. In: Kaye, T.N.; Liston, A.; Love, R. M.; Luoma, D.L.; Meinke, R.J.; Wilson, M.V., editors. Conservation and Managemnet of Native Plants and Fungi. Native Plant Society of Oregon. Corvalis, Oregon. p 296.

Electronic Sources

(2000). CalFlora: on California plants for education, research and conservation. [web application]. Berkeley, California: The CalFlora Database [a non-profit organization]. http://www.calflora.org/.. Accessed: 2002.

(2002). Endangered Species Network (ESIN). Pacific Biodiversity Institute, Winthrop, WA. http://www.pacificbio.org/ESIN/ESIN.html. Accessed: 2002.

Gillett, J.M.; Consaul, L.L.; Aiken, S.G.; Dallwitz, M.J. (1999 onwards). Fabaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Retrieval. Version: 15th November 2000. http://www.mun.ca/biology/delta/arcticf/. Accessed: 2002.

ONHDB. (2000). Oregon Natural Heritage Program Database. Portland, Oregon.

Journal Articles

1936. (Original Publication). Proc. Biol. Soc. Wash. 49: 111.

Barroetavena, C.; Gisler, S.D.; Luoma, D.L.; Meinke, R.J. 1998. Mycorrhizal status of the endangered species Astragalus applegatei Peck as determined from a soil bioassay. Mycorrhiza. 8, 2: 117-119.

Parenti, R. 1993. Endangered and threatened wildlife and plants; Determination of endangered status for the plant Astragalus applegatei (Applegate's milk-vetch). Federal Register. 58, 143: 40547-40551.

Raven, A. 1999. Aese's Onion: A Rare Plant with an Urban Life. The Berry Botanic Garden Newsletter. 12, 2: 4-5.

USFWS. 1991. Proposed Endangered Status for a Plant, Astragalus applegatei (Applegate’s Milk-Vetch). Federal Register. 56, 228: 59917-59920.

USFWS. 1992. Listing Proposals. Endangered Species Technical Bulletin. 17, 1-2: 9-10.

USFWS. 1993. Determination of Endangered status for the plant Astragalus applegatei (Applegate’s milk-vetch). Federal Register. 58, 143: 40547-40551.

USFWS. 1999. Species Update: Region 1. Endangered Species Bulletin. 24, 6: 24.

Reports

Borgias, D. 2001. Population Status of Astragalus applegatei at the Ewauna Flat Preserve, Klamath County, Oregon. v.2. The Nature Conservancy Report.

Gisler, S.; Meinke, R.J. 1998. Cultivation and outplanting of ApplegateÆs milk-vetch (Astragalus applegatei). Progress Report (1995-1996) for the U.S. Fish and Wildlife Service.

Gisler, S.; Meinke, R.J. 2001. Conservation of the endangered species, ApplegateÆs Milkvetch (Astragalus applegatei). Part I: Soil symbionts and cultivation. Part II: Transplanting and population establishment. Prepared for the Region 1 U.S. and Wildlife Service.

Larkin, G.; Salzer, D. 1992. A plant demography study of Delphinium leucocephalum, Thelypodium howellii ssp. spectabilis, Astragalus applegatei, and Lilium occidentale: preliminary report 1990û1991. Portland, Oregon: The Nature Conservancy, Oregon Field Office.

USFWS. 1998. Applegate's milk-vetch (Astragalus applegatei) recovery plan. Portland, Oregon: U.S. Fish & Wildlife Service, Pacific Region. p.41.


  This profile was updated on 7/8/2010
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