Lupinus danaus was described from a collection made by Henry N. Bolander (#5087) labeled as "12,500 ft" on Mt. Dana [see the image of the isotype US321123 above, oriented as in nature]. In the Jepson Manual, the taxon is not treated. Munz & Keck (1959) treated it as a variety of L. lyallii. Variation in the Lupinus lepidus group is complex: Barneby (Intermountain Flora Vol. 3B 1989) offered a classification that placed these dwarf perennial lupines in context, but did not deal directly with the var. danaus since it is considered exclusively Sierran.
This summer I observed Lupinus danaus in vegetation sampling many times. The holotype and the plants in the field share the feature of having prostrate, very sparsely leafy peduncles that arch upwards only distally, such that the inflorescence is displayed upright at a short 1-3 inch distance from the actual rosette, which is very sparsely leafy indeed. This feature is not one that I have seen in photos of Lupinus lepidus var. lobbii, and it in fact may be a feature equal to those which Barneby used to recognize other variants of Lupinus lepidus, and hence the combination Lupinus lepidus var. danaus might be indicated. Thus, at least as the plants appear in the field, they differ consistently from var. lobbii, which has relatively shorter erect peduncles [Barneby's "development and attitude of peduncles"] or perhaps also "spatial relationship between foliage and raceme".
Whether or not the peduncle feature of the putative var. danaus is under genetic control is the central question.
Munz & Keck (1959) gave the range of Lupinus danaus as "Sierra Nevada north to Warner Mtns, w. Nev." [the latter would be Mount Rose, NV].
below I have scanned Barneby's comments verbatum [ my emphasis added] from Intermountain Flora p. 257 for consideration of the problem:
Dwarf perennial lupines are far less numerous in the Intermountain region than the teeming multitudes of L. argenteus, but they are almost as difficult to classify and consequently have acquired similarly extensive literature and synonymy. The characters that contribute to the individuality of an individual plant, to a population of similar plants, or to a conceptually idealized taxon are almost all quantitative and without exception independently variable. The most obvious are the degree of caulescence and mode of branching, the length and orientation of hairs, the size of leaves, the development and attitude of peduncles, the spatial relationship between foliage and raceme, the average length of raceme and density of flowers along its axis, and the size of petals. From early times these have been the external markers by which taxonomists have attempted to discover comprehensible order in this vexatiously difficult group. Detling's analysis of L. lepidus and kindred forms (1951) demonstrated the continuity of variation in all observed character states, and his conservative taxonomy, strongly conditioned by facts of dispersal and ecology, was adapted by Hitchcock (1961) to the dwarf lupines of the Northwestern flora and best harmonizes with standards accepted elsewhere in Fabaceae. It cannot be denied that a measure of undesirable simplification is inherent in this approach to Lupinus. Indefinitely numerous individual populations of dwarf lupines or small groups of such adapted to a particular habitat or confined to a particular region certainly do possess an idiosyncratic facies derived from a particular syndrome of characters. They are especially marked among geographically disjunct alpine or subalpine races of the aggregate L. lepidus var.lobbii and among the races of var. aridus remotely scattered in austere valley habitats over eastern Nevada and southeastern Oregon, no two of which seem exactly alike at all points. Undue emphasis on differences between these minor races leads inexorably to the quick sands that ultimately engulfed Charles Piper Smith. On the other hand wider, more comprehensive specific and infraspecific concepts suffer progressively from lack of definition. Most varieties of L. lepidus are truly dwarf lupines, with low tufted or diffusely matted foliage and stems reduced to a few short internodes or to columnar caudex-branches sheathed in stipules. The vars. confertus and ramosus however, have well developed primary stems sometimes giving rise to axillary fertile branchlets and therefore resemble in habit forms of L. argenteus. The dorsally glabrous banner and persistent floral bracts either singly or together distinguish these taller varieties of L. lepidus from all of L. argenteus.