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Astragalus missouriensis Nutt. var. mimetes Barneby


Family: Fabaceae

Synonyms: None

Vernacular Name: Mimic milk-vetch

Description: Tufted perennial from a taproot; foliage silvery-gray strigose with malpighian hairs; stems erect to spreading, 0-7 mm long; stipules distinct, 2.5-4 mm long; leaves pinnately compound, 3-6.5 cm long, bearing 4-6 pairs of elliptic leaflets 3-12 mm long; peduncles 4-17 cm long, bearing 4-15 flowers held well above the leaves; calyx 4.5-5.8 mm long, the teeth triangular or subulate; petals bright pink-purple or violet-red, the banner 9-11.8 mm long; pod ascending, 1-chambered, 14-24 mm long, subsymmetrically oblong or oblong-elliptic in outline, straight or slightly curved, usually more or less bicarinate by the thickened sutures, slightly dorsiventrally compressed, tapered to a sharp, laterally compressed beak, the walls thinly strigulose, at first fleshy, at maturity stiffly leathery; ovules 36-46.

Similar Species: The smaller forms of Astragalus missouriensis var. mimetes are barely distinguishable from Astragalus missouriensis Nutt. var. accumbens (Sheld.) Isely (as recognized by Isely, 1998), or Astragalus accumbens Sheld. (as recognized by Barneby, 1964, or Welsh, 2007). The vernacular name alludes to this similarity. The following table is drawn from the key in Isely (1998) except for the number of ovules in an ovary, which is drawn from Barneby (1964), repeated in Welsh (2007). All authors agree on the attributes purportedly separating the taxa, whether A. accumbens is recognized at the specific or infraspecific level.

  mimetes accumbens
Calyx length, mm 5-6 4.5-5
Corolla colorpink-purpleochroleucous or lavender tinged
Corolla length9.5-11.5 mmup to 9 mm
Standard reflexedto ca. 45°ca. 90°
Keel incurvedca. 90°110-120°
# of ovules36-4622-32

Astragalus accumbens occurs slightly to the west of the northern portion of the geographic range of A. missouriensis var. mimetes, in and around the Zuñi Mountains on stiff alkaline clays.

Distribution: New Mexico, Cibola, Sandoval, Socorro and Valencia counties, mostly on the west side of the Río Grande, but occuring a few kilometers east of the river in Socorro Co. The total geographic range of var. mimetes is ca. 142 miles N-S (227 km), and 75 miles E-W (120 km).

Habitat: Open gravelly or sandy limey knolls, slopes, road cuts, and arroyos in piñon-juniper woodland or sagebrush rangeland; 1400 - 1900 m (4600  6200 ft).

Remarks: Astragalus missouriensis var. mimetes has been reported as far north as Los Alamos Co. but that record is based upon a misidentified specimen of A. missouriensis var. missouriensis (Tierney & Fox 9, UNM). All authors agree that A. missouriensis var. mimetes is very similar to A. missouriensis var. accumbens, the latter purportedly having smaller flowers, dull coloration, and fewer ovules. Nevertheless, specimens of var. mimetes from Valencia Co., eastern Cibola Co., and north-central Socorro Co., have calyces 5 mm long or less in length, and a banner of 9 mm long or less, dimensions well within the range for those structures in the var. accumbens, and outside the range allowed for the var. mimetes. In a review of specimens no apparent differences were seen in degree of reflexion of the banner or the curve of the keel. The most easily seen feature distinguishing the var. mimetes from the var. accumbens is the color of the petals, brilliant red-purple in the former, dull ochroleucous often tinged with lilac in the latter. Welsh (2007) follows Barneby (1964) with regard to the number of ovules in the ovary or developing pod. The var. mimetes is said to have more ovules than the var. accumbens (see table above), but it is apparent that no one has corroborated this feature since Barneby's treatment of the genus, at which time many fewer specimens were available. All in all, smaller forms of the var. mimetes can be distinguished from var. accumbens only by flower color and perhaps ovule number.

Important Literature (*Illustration):

Barneby, R. C. 1964. Atlas of North American Astragalus. Memoirs of the New York Botanical Garden 13:1-1188.

Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States (Excluding Alaska and Hawaii). Monte L. Bean Life Science Museum, Brigham Young University, Provo.

*Welsh, S. L. 2007. North American species of Astragalus Linnaeus (Leguminosae), A taxonomic revision. Monte L. Bean Life Science Museum, Brigham Young University, Provo.

Information Compiled By: Richard Spellenberg, 2007.


Photo credits in header Peniocereus greggii var. greggii © T. Todsen,
Lepidospartum burgessii © M. Howard, Argemone pleiacantha ssp. pinnatisecta © R. Sivinski
Design: J. Mygatt; Copyright © 1999-2005 New Mexico Rare Plant Technical Council