Astragalus cremnophylax - Barneby
Cliff Milkvetch
Taxonomic Status: Accepted
Related ITIS Name(s): Astragalus cremnophylax Barneby (TSN 25481)
Unique Identifier: ELEMENT_GLOBAL.2.142809
Element Code: PDFAB0F2H0
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 cremnophylax
Taxonomic Comments: A distinct species in one of the largest genera of flowering plants. Taxon previously referred to Astragalus humillimus (Kearney & Peebles, 1960). Barneby looked at the three varieties and determined that the differences between them are not significant; however, based on their being spatially disjunct (no possiblity of pollen exchange) he now recognizes them at the varietal level. Full species (collectively) is very distinct.
Conservation Status
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NatureServe Status

Global Status: G1G2
Global Status Last Reviewed: 03Nov2011
Global Status Last Changed: 03Nov2011
Rounded Global Status: G1 - Critically Imperiled
Reasons: Endemic to Arizona and known from at least 3 disjunct locales: the South Rim of the Grand Canyon (the typical variety), the Buckskin Mountains near the northern end of the Kaibab Plateau (var. myriorrhaphis), and Navajo land on the east side of Marble Canyon (var. hevronii). Plants recently found on the North Rim of the Grand Canyon may be var. cremenophylax, or may warrant distinction at the varietal level. All populations are restricted to Kaibab Limestone, and all seem to be restricted to a particular lens of this rock and to extremely harsh, xeric microclimates. All the named varieties, especially the typical, are exhibiting reproductive problems involving lethal genes that cause embryo abortion.
Nation: United States
National Status: N1N2

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 Arizona (S1S2), Navajo Nation (SNR)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS

NatureServe Global Conservation Status Factors

Overall Threat Impact Comments: The typical variety was severely trampled by park visitors because the plants grow at the edge of the rim - where there are spectacular views. The area has now been fenced. However, the typical variety is possibly being outcompeted by caespitose rockmat (Nancy Bryan, Grand Canyon NP, pers. comm.). An informal trail traverses a population of var. myriorrhaphis; however, var. myriorrhaphis seems to have very few threats (AGFD 1992). Reproductive problems (a large percentage of aborted embryos) may threaten all the varieties.

Short-term Trend Comments: Since the area has been fenced, the typical variety seems to be thriving even though reproduction is sporadic. The population trend of var. myriorrhaphis is apparently stable (AGFD 1992).

Other NatureServe Conservation Status Information

Distribution
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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.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States AZ, NN

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AZ Coconino (04005)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
15 Lower Colorado-Marble Canyon (15010001)+, Grand Canyon (15010002)+, Kanab (15010003)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A pale gray-green, mat-forming, long-lived perennial herb, usually less than 2 cm high. Flowers are white to pale purple.
Terrestrial Habitat(s): Cliff, Forest/Woodland, Woodland - Conifer
Habitat Comments: Fissures in pale, highly reflective Kaibab Limestone pavement. Usually in exposed, unshaded, situations near canyon rims, where hot updrafts and high winds create especially xeric conditions.
Plants grow in the uppermost layer of a very peculiar white layer of limestone that is not grossly fractured, but rather weathers in small, shallow pockets and networks of small cracks. This type of limestone (Kaibab limestone) is exposed for only a few hundred square yards, forms large flat platforms, has shallow soils (<7 cm deep), is unshaded, and in the pinon-juniper-cliffrose plant community above 1219 m (4000 ft). In these openings, sentry milk-vetch is co-dominant with rock mat (Petrophytum caespitosum) (Arizona Game and Fish Department 2005).

Economic Attributes
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Economically Important Genus: Y
Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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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: 01Aug1989
NatureServe Conservation Status Factors Author: Gardner, P.A., rev. Maybury (1997), rev. A. Olivero (2003)

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).

References
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  • Arizona Game and Fish Department. 2005. Astragalus cremnophylax var. cremnophylax Barneby. Unpublished abstract compiled and edited by the Heritage Data Management System, Arizona Game and Fish Department, 9 pp.

  • Arizona Game and Fish Department. 1992. Astragalus cremnophylax var. myriorrhaphis. Unpublished abstract compiled and edited by the Heritage Data Management System, Arizona Game and Fish Department, Phoenix, Arizona. 4 pp.

  • Arizona Game and Fish Department. 1999. Astragalus cremnophylax var. hevronii. Unpublished abstract compiled and edited by the Heritage Data Management System, Arizona Game and Fish Department, Phoenix, Arizona. 2 pp.

  • Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.

  • 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.

  • Kearney, T.H., R.H. Peebles, and collaborators. 1951. Arizona flora. 2nd edition with Supplement (1960) by J.T. Howell, E. McClintock, and collaborators. Univ. California Press, Berkeley. 1085 pp.

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