CPC National Collection Plant Profile

Astragalus cremnophylax var. cremnophylax

Photographer:
Sue Rutman

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CPC National Collection Plant Profile

Astragalus cremnophylax var. cremnophylax


Family: 
Fabaceae  
Common Name: 
sentry milkvetch
Author: 
Barneby
Growth Habit: 
Forb/herb
CPC Number: 
391

Distribution
Protection
Conservation
References


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Astragalus cremnophylax var. cremnophylaxenlarge
Photographer: Sue Rutman
sue_rutman[at]nps.gov

Astragalus cremnophylax var. cremnophylaxenlarge
Photographer: Sue Rutman
sue_rutman[at]nps.gov


Astragalus cremnophylax var. cremnophylax is Not Sponsored
Primary custodian for this plant in the CPC National Collection of Endangered Plants is: 
Joyce Maschinski, Ph.D. contributed to this Plant Profile.

 
Astragalus cremnophylax var. cremnophylax


Sentry milk-vetch is a rock-hugging plant that literally grows in sites that overlook the Grand Canyon. It's scientific name means 'gorge watchman'. The population where this plant was first collected was threatened by trampling from the millions of visitors to Grand Canyon National Park. In 1990, the Park Service erected a fence to re-route traffic around the sentry milk-vetch. Since protection, this population has thrived, increasing in numbers 4-fold. New locations where plants grow along the rim have been discovered; one site has only 2 plants growing on a Kaibab limestone platform about the size of a dinner table. A second site, on the north rim of Grand Canyon, is fairly remote and free from trampling pressure. (Maschinski & Rutman 1993)

Distribution & Occurrence

State Range
  Arizona
State Range of  Astragalus cremnophylax var. cremnophylax
Habitat
  This species grows on a white layer of Kaibab limestone with little or no soil in unshaded openings in the pinyon-juniper-cliffrose plant community (Maschinski & Rutman 1993).

Sentry milk-vetch grows in association with rock mat (Petrophytum caespitosum). (Maschinski & Rutman 1993)

Distribution
  Known only from the south and north rim of Grand Canyon within the National Park (Maschinski & Rutman 1993).

Number Left
  The three populations of this species are located within Grand Canyon National Park. Two known populations occur on the South Rim of the Grand Canyon, where one site has 2 living individuals and the other site has approximately 1000. On the north rim on several Kaibab limestone fingers jutting into the canyon, there are approximately 1500 individuals. The north rim populations are undergoing taxonomic scrutiny to determine if they are in fact the same variety. (Maschinski & Rutman 1993)

Protection

Global Rank:  
G1T1
 
1/20/1999
Guide to Global Ranks
Federal Status:  
LE
 
10/24/1996
Guide to Federal Status
Recovery Plan:  
Yes
 
1/1/1993

State/Area Protection
  State/Area Rank Status Date  
  Arizona S1 8/1/2002  

Conservation, Ecology & Research

Ecological Relationships
  These plants occupy a unique niche - tiny cracks in limestone pavement. Plants flower in response to moisture in the spring and fall. There are two bouts of seed set. (Maschinski & Rutman 1993)

Threats
  Threats include:
Foot traffic
Low genetic variation
Poor seed production
(NatureServe Explorer 2002)

Current Research Summary
  The genetic diversity of the live sentry milk-vetch plants in the National Collection is being compared to the genetic diversity of the wild population (Maschinski and Travis, in prep).
The Center for Research of Endangered Wildlife is investigating using tissue culture techniques to propagate sentry milk-vetch.
Reproductive success and the possibility of inbreeding depression in the wild populations is being investigated by Allphin et al. (in prep).

Current Management Summary
  Grand Canyon National Park personnel monitor the populations of sentry milk-vetch to determine whether populations are stable, growing or declining. Fencing the largest south rim population has been a great and inexpensive conservation success story. (Maschinski & Rutman 1993)

Research Management Needs
  The number of secure populations in the wild is so few that the recovery plan (in prep as of 5/15/01) suggests introductions to new habitats as possible safeguards against extinction. Generating enough propagules for introduction is a great research need.

Ex Situ Needs
  There is a great need to investigate ways to propagate large numbers of individuals if reintroduction is to ever be a possibility. Tissue culture is one of the areas being investigated.

References

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.

Pavlovic, N.B. 1994. Disturbance-dependent persistence of rare plants: anthropogenic impacts and restoration implications. In: Bowles, M.L.; Whelan, C., editors. Recovery and Restoration of Endangered Species. Cambridge University Press. Cambridge. p 159-193.

Conference Proceedings

Allphin, L.; Weins, D.; Brian, N.J.; Randall, P. Reproductive success and genetic divergence among varieties of the rare and endangered Astragalus cremnophylax from Arizona, USA. (Oral presentation). 3rd Southwestern Rare and Endangered Plant Conference; September 25-28, 2000; Nothern Arizona Universiy, Flagstaff, AZ. 2000.

Maschinski, J. Integrated conservation strategies for recovery of Astragalus cremnophylax var. cremnophylax at the South Rim of Grand Canyon National Park. First Biennial Conference on Research at Flagstaff; 1991; Flagstaff, AZ.

Maschinski, J.; Rutman, S. The Price of Waiting May be Too High: Astragalus cremnophylax var. cremnophylax at Grand Canyon National Park. Proceedings of the Southwestern Rare and Endangered Plant Conference; 30 March - 2 April; Santa Fe, NM. In: Sivinski, R.; Lightfoot, K., editors. 1992. New Mexico Forestry and Resources Conservation Division. p 181-187.

Electronic Sources

NatureServe. (2008). NatureServe Explorer: An online encyclopedia of life [web application]. [Internet].Version 7.0. NatureServe, Arlington, Virginia. http://www.natureserve.org/explorer. Accessed: (June 17, 2008).

Journal Articles

Allphin, L.; Weins, D.; Brian, N.; Randall, P. in prep. Reproductive success and genetic divergence among varieties of the rare and endangered Astragalus cremnophylax from Arizona, USA.

Fonseca, J. 1992. Southwestern Rare and Endangered Plant Conference. The Plant Press. 16: 6-7.

Maschinski, J.; Frye, R.; Rutman, S. 1997. Demography and population viability of an endangered plant species before and after protection from trampling. Conservation Biology. 11, 4: 990-999.

NPS. 1998. Colorado Plateau: Grant funds endangered plant monitoring. Park Science: Integrating Research and Resource Management. 18, 1: 5.

Rowlands, P.G.; Brian, N.J. 1996. A perimeter tracing method for estimating basal cover: Monitoring the endangered sentry milk-vetch at Grand Canyon National Park, Arizona. Southwestern Naturalist. 41, 2: 169-178.

Rutman, S. 1988. Sentry Milk Vetch. The Plant Press. 12: 9.

Travis, S.E.; Maschinski, J.; Keim, P. 1996. An analysis of genetic variation in Astragalus cremnophylax var cremnophylax a critically endangered plant, using AFLP markers. Molecular Ecology. 5, 6: 735-745.

U.S. Fish & Wildlife Service. 1989. Listing proposals: sentry milk-vetch (Astragalus cremnophylax var. cremnophylax). Endangered Species Technical Bulletin. 16, 11-12: 5.

USFWS. 1976. Proposed Endangered Status for 1700 U.S. Plants. Federal Register. 41: 24523-24572.

USFWS. 1988. Regional News--Regions 2, 4 & 5. Endangered Species Technical Bulletin. 13, 6-7: 3, 6.

USFWS. 1989. Proposed Endangered Status for Astragalus cremnophylax var. cremnophylax (sentry milk-vetch). Federal Register. 54, 200: 42820-42822.

USFWS. 1990. Determination of Endangered Status for the Plant Astragalus cremnophylax var. cremnophylax (Sentry Milk-vetch). Federal Register. 55, 234: 50134-50137.

Magazine Articles

Maschinski, J. 1997. An Update on Research. The Arboretum at Flagstaff: 14. 1. 1-6.

Reports

2002. General Species Information. Phoenix, Arizona: Arizona Ecological Services Field Office.

Maschinski, J. 1990. Propagation of Astragalus cremnophylax var. cremnophylax and reintroduction to the South Rim of Grand Canyon National Park. Flagstaff, AZ: The Arboretum at Flagstaff.

Maschinski, J. 1990. Reintroduction of Astragalus cremnophylax var. cremnophylax. Flagstaff, AZ: The Arboretum at Flagstaff.

USFWS. 1993. Sentry milk-vetch (Astragalus cremnophylax var. cremnophylax) recovery plan. Albuquerque, New Mexico: U.S. Fish & Wildlife Service, Region 2. p.34.


  This profile was updated on 9/28/2010
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