Flora of North America species comparison

Dodecatheon hendersonii occurs from southern Vancouver Island in the coastal ranges to west-central California (as far as San Benito County) and is disjunct into the San Bernardino Mountains in southern California. To the east, the species is found on the Siskiyou Mountains and in the Sierra Nevada of California to Tulare County. A Macoun (s.n., DAO) specimen supposedly gathered at Yale, British Columbia, may be misattributed (K. I. Beamish 1955); all other known localities are from Vancouver Island.

Inasmuch as bulblets and mature capsules are rarely collected, it is difficult to clearly distinguish between var. hendersonii and var. hansenii. The former may be broadly characterized as plants bearing bulblets at anthesis with sparsely glandular scapes, pedicels, and, sometimes, calyces. The calyx of var. hendersonii is usually greenish with purple or reddish speckles. The most distinctive characteristics of this phase are a filament tube that is 1–2.5 mm wide and acute anther apices. It is found mainly along the coast from British Columbia to southern Oregon and in scattered locations in coastal California, with disjunct populations in the foothills of the central Sierra Nevada, and in the mountains of southern California. Variety hansenii is glabrous, lacks bulblets, and the calyx typically is green; it usually is found inland in the Siskiyou Mountains and the Sierra Nevada and scattered populations occur in the coastal ranges of northern California. The filaments in var. hansenii are broader, being tubes 1.5–4 mm wide, and anther apices are obtuse. Capsules of var. hendersonii are usually operculate; those of var. hansenii appear to be consistently valvate. The 2n = 66 plants appear to be primarily individuals that produce little or no pollen.

Adding to the complexity is the close association of var. hansenii with Dodecatheon clevelandii var. patulum. The latter, like var. hendersonii, is basically a diploid or a tetraploid (2n = 44, 88), rather than a hexaploid, and one would expect no crossing between the two. Nonetheless, H. J. Thompson (1953) reported finding sterile individuals where D. hendersonii var. hansenii and D. clevelandii var. patulum were in close association. These sterile individuals were morphologically similar to var. hansenii (and not intermediate between the two), and sterile individuals were fairly common in populations of var. hansenii where no other Dodecatheon were present. Although the three entities may be characterized (see table 5 in Thompson), Thompson concluded that assigning names to some populations was difficult and could be established “only by a detailed consideration and summation of all the characters.”

H. J. Thompson (1953) recognized Dodecatheon hansenii; A. F. Cholewa and D. M. Henderson (1993) accepted only D. hendersonii. In their molecular study, A. R. Mast et al. (2004) considered the two entities distinct, albeit closely related, species. It is possible that var. hansenii had a hybrid origin involving var. hendersonii and D. clevelandii var. patulum, and backcrossing with var. hendersonii resulting in a series of morphological features that allies the hansenii phase more to D. hendersonii than to D. clevelandii. More study is needed, especially in areas where the two appear to have overlapping ranges in the Bay Area and Sierra Nevada foothills of California.

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

Dodecatheon amethystinum is found mainly on, and at the bases of, limestone cliffs in hardwood forests from southwestern Wisconsin and adjacent southeastern Minnesota to northeastern Iowa, western Illinois, and eastern Missouri. It is disjunct to the eastern Appalachian Mountains of southeastern Pennsylvania; reports from northern West Virginia are based on specimens of D. meadia. Vegetatively, D. amethystinum is allied to D. meadia although its thin-walled (rather than thick and firm) fruit is like that of D. pulchellum. The only truly distinguishing feature between it and D. meadia is the fully mature capsules (L. H. Klotz and C. Loeffler 2007). In D. amethystinum, length of the light to reddish brown or yellowish capsule often is more than three times the diameter. The length of the dark reddish brown capsule of D. meadia is less than three times the diameter. As noted by H. H. Iltis and W. M. Shaughnessy (1960), D. amethystinum tends to grow on moist cliff faces and bluffs; D. meadia tends to occur on drier sites in prairie settings and in deciduous woodlands. Dodecatheon meadia is sometimes found in moist areas, and even on cliff faces; these sites are still comparatively drier. According to A. F. Cholewa, some populations in southern Minnesota that she considers to be D. amethystinum have leaves that are relatively broad and tend not to taper gradually to the petiole. In that light, continued recognition of D. amethystinum at the species level becomes dubious.

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