Astragalus lentiginosus var. kernensis (Jeps.) Barneby
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
"High Sierra Nevada of Tulare Co., Volcano Creek, 8200 ft. (Jepson 4930, type)." Holotypus, labeled G"Golden Trout Creek," an earlier name for Volcano Creek, collected 2 July, 1912, UC-JEPS!
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Synonyms
Astragalus kernensis Jeps., Cystium kernense (Jeps.) Rydb., Astragalus kernensis subsp. charlestonensis Clokey, Astragalus lentiginosus var. charlestonensis (Clokey) Barneby
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Description
Variety Description - Slender perennial, strigulose with subappressed hairs up to 0.25-0.45 (0.5) mm. long, the herbage green or greenish-cinereous, the leaflets glabrous or nearly so above; stems prostrate or decumbent, 2.5-12 cm. long, the internodes all short, up to 1.8 cm. long but mostly less; leaves 1-5 cm. long, with short and slender petiole and (7) 11-19 remote or crowded, elliptic-oblanceolate, oval, or obovate, obtuse or emarginate, mostly conduplicate and recurved leaflets 1.5-7 mm. long; peduncles 0.6—2.5 cm. long; racemes loosely but shortly (2) 3—9-flowered, the axis 0.3-1.5 cm. long in fruit; calyx 4.1-5.3 mm. long, the tube cylindric or cylindro-campanulate, 3.5—4.6 mm. long, 1.7—2.5 mm. in diameter, the teeth 0.6—1.2 mm. long, petals whitish; banner 9.3—11.3 mm. long, 4.2—6 mm. wide; wings 8.6-10.8 mm., the blades 4.8-6.7 mm. long; keel 7.3-8.7 mm., the blades 3.5-4.5 mm. long; pods gathered into loose or compact, humistrate clusters, the bladdery-inflated, globose or very broadly and plumply ovoid or obovoid body 6-13 mm. long, 6—10 mm. in diameter, rounded or subcordate at base, truncate or obscurely umbilicate at apex where abruptly contracted into an erect, linear- or subulate-tubular, cusplike beak, the papery, subdiaphanous, pale green or stramineous, purple-mottled but ultimately brownish valves thinly and loosely strigulose, the complete septum 2-4 mm., the funicular flange 0.4-1.5 mm. wide; ovules (7) 10-18.
Distribution and Ecology - Dry gravelly or sandy slopes and flats, locally plentiful in two widely separated and narrowly restricted areas: among sagebrush and in lodgepole pine forest, on granite, 7800—8500 feet, Kern Plateau just west of the Sierra Crest in Tulare County, California (Volcano Creek; Templeton, Monache, and Troy meadows); and with bristlecone pine, on limestone, 10,000-10,500 feet, about the summit of Charleston Peak, Clark County, Nevada.—Map No. 128.—June and July.
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Discussion
The var. kernensis, the most delicately fashioned of all forms of the protean A. lentiginosus, closely resembles the most slender phases of var. ineptus from high on the east slope of the Sierra Nevada. The flowers are usually somewhat fewer but essentially of the same form and size except for a slightly shorter calyx. The unique features of var. kernensis are the small size of the fruit and the modification of its beak into a narrow, tubular structure resembling a persistent style. However, the beak is sometimes a little broader at base than distally, subulate rather than linear in profile, and then a trifle compressed laterally, and although always much narrower than the triangular or deltoid beak elsewhere characteristic of A. lentiginosus, is not fundamentally different in structure.
Since my revision of A. lentiginosus (1945) the Sierran populations of var. kernensis have become better known through admirable sets of specimens collected on the headwaters of the South Kern River by J. T. Howell. The variation now known to occur in a small area between Templeton and Monache meadows has fatally undermined, if not wholly demolished the supposed differential characters of var. charlestonensis, which I maintained as distinct on the basis of a larger pod and more numerous leaflets (1945, p. 77, in clave). I now find that in the Sierra the leaflets range in number from 11 to 19, while the pod varies in length from 6 to 10 mm. On Charleston Peak the leaflets are of the same size and number and the pod varies from 6 to 13 mm. in length. The Nevadan plants do seem to differ slightly in the commonly wider septum (and correspondingly less deeply sulcate ventral suture) and in the slightly larger seeds. It might be added that the ovules are commonly 15-18 (but occasionally as few as 7) in the Sierra and only 10-15 on Charleston Peak. These, however, seem insubstantial characters to balance against the close essential similarities in all other respects, and var. charlestonensis is accordingly treated here as a minor variant.
The notable bicentric distribution of var. kernensis is bound to excite speculation as to its age and origin, particularly against the background of its species and section. Floristic relationships between the Sierra Nevada and the Charleston Range are few but can be traced feebly northwest through the White Mountains and directly westward, across the now impassable gap of the Mohave Desert, through the San Bernardino and San Gabriel Mountains. Interestingly enough, each of these mountain masses is occupied by an endemic form of A. lentiginosus, the White (and Inyo) Mountains by var. semotus, the east slope of the Sierra escarpment by var. ineptus, and the Transverse Ranges by vars. sierrae and antonius respectively. There can be no doubt that all are very closely related to var. kernensis, and the question arises as to whether a parallel modification has not arisen separately in the two areas; but the number of coincidences required cannot appear likely to the rational mind. Granted that the populations of var. kernensis in its two foci of distribution are monophyletic in origin, and that neither stems from a chance introduction (which seems to the highest degree improbable), it must be assumed that the ancestral stock was much more widely distributed formerly than it is today. In some relatively moist and cool periods during the Pleistocene var. kernensis could have migrated across or around the north periphery of what is now the Mohave Desert and become confined to its present refugia as aridity increased. Yet it is puzzling that ecologically suitable refuges adjacent to the Mohave are occupied today by other races of A. lentiginosus. Did var. kernensis never reach these bordering ranges? Did it reach them and there become assimilated or submerged by a later invasion of a younger and more vigorous offshoot of its species? I have no answers to these questions. The history of var. kernensis must be more complex and probably reaches back further into the past than that of the other forms of A. lentiginosus to which it is most closely allied.
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Objects
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Distribution
Nevada United States of America North America| California United States of America North America|