Flora of North America species comparison

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Astragalus amphioxys var. modestus

Astragalus amphioxys var. amphioxys
Photo is of parent taxon

crescent milkvetch, modest milkvetch
Photo is of parent taxon

crescent milkvetch
Flowers

calyx cylindro-campanulate, tube 6.1–9.3 mm, lobes 1.1–2.6 mm;

corolla banner 12.8–16 mm;

keel 11–12.7 mm.

calyx cylindric, tube (5.8–)7–10.5 mm, lobes 1.5–3.7(–4.5) mm;

corolla banner (16.2–)19–24.5 mm;

keel (13.2–)14.3–18.8(–19.6) mm.
Legumes

16–40 mm, crescentic or incurved through 1/2 their length.

15–40 mm, curved.
Seeds

44–58.

(42–)44–56.
2n

= 22.

Astragalus amphioxys var. modestus

Astragalus amphioxys var. amphioxys
Phenology Flowering Mar–May. Flowering late Mar–Jun.
Habitat Dry gravelly hillsides, in blackbrush, four-wing saltbush, Indian ricegrass, needle-and-thread grass, old man sagebrush, mixed grass communities, on sandy silt, limestone, or cindery volcanic debris. Sandy valleys, plains, gravelly hillsides, on dunes, rarely on gumbo-clay flats, in creosote bush, Joshua tree, blackbrush, indigo bush, salt desert shrub, pinyon-juniper, and mountain brush communities.
Elevation 1100–1500 m. (3600–4900 ft.) 400–2100 m. (1300–6900 ft.)
Distribution
from FNA
AZ; NV; UT; Dry gravelly hillsides; in blackbrush; four-wing saltbush; Indian ricegrass; needle-and-thread grass; old man sagebrush; mixed grass communities; on sandy silt; limestone; or cindery volcanic debris
[BONAP county map]
from FNA
AZ; CO; NM; NV; TX; UT; Mexico (Chihuahua)
[BONAP county map]
Discussion

The small-flowered var. modestus forms the other major extreme in flower size within the species, contrasting with the large-flowered var. vespertinus. It is local, forming uniform colonies within the range of var. amphioxys but only from valleys affluent to the Colorado River from San Juan and eastern Kane counties, Utah, and northern Mohave County, Arizona, with disjunct populations in Lincoln County, Nevada. Some plants from northeastern Arizona and northwestern New Mexico have similarly small flowers and might represent an eastward extension of var. modestus; however, in this case introgression from Astragalus missouriensis cannot be ruled out.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Variety amphioxys is variable and includes elements that may be taxonomically significant (D. Isely 1998).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Astragalus > sect. Argophylli > Astragalus amphioxys Fabaceae > subfam. Faboideae > Astragalus > sect. Argophylli > Astragalus amphioxys
Sibling taxa
A. amphioxys var. amphioxys, A. amphioxys var. musimonum, A. amphioxys var. vespertinus
A. amphioxys var. modestus, A. amphioxys var. musimonum, A. amphioxys var. vespertinus
Name authority Barneby: Leafl. W. Bot. 9: 89. (1960) unknown
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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