Flora of North America species comparison

There is a historical record of Zeltnera exaltata from Montana. An old record from Nebraska is considered to be based on an adventive occurrence of short duration.

G. Mansion and L. Zeltner (2004) reported that plants compatible with descriptions of Zeltnera exaltata and similar in molecular characters included some populations with 2n = 40 and others with 2n = 74. They considered the latter likely to be of allopolyploid origin, derived from the hybridization of a diploid component of Z. exaltata in the narrow sense with a species having 2n = 34. Plants in the South Coastal Ranges from Baja California north to Monterey County, California, from which region Mansion and Zeltner reported 2n = 40, have smaller flowers, with the closed corollas 10–14 mm, subglobose seeds 0.25–0.33 mm in diameter, and pollen ca. 22 µm in diameter (C. R. Broome 1973). Plants (except those less than 10 cm) from localities farther inland and northward, from regions in which Mansion and Zeltner found 2n = 74, have corollas 14–20 mm, ellipsoid seeds 0.5–0.75 mm long, and pollen grains ca. 30 µm in diameter. By typification, the name Z. exaltata in the narrow sense is applicable to the entity occurring in the more northern and inland localities, with 2n = 74; if the species should be divided, it is the populations of the South Coastal Ranges, with 2n = 40, that should be treated as new. None of the names listed in the synonymy of Z. exaltata by Broome and Mansion (2004) is typified by specimens from the South Coast Ranges.

Zeltnera exaltata varies greatly in the number of stems arising from the base, the presence or absence of basal leaves at flowering time, and, especially in its easternmost populations, leaf width. The narrow angle of branching and the long pedicels generally give plants of this species a distinctive appearance. Its corollas are usually four-merous, whereas five-merous corollas prevail in the other Zeltnera species in the flora area (although four-merous corollas are not uncommon in Z. nudicaulis), and the corolla lobes, being about half as long as the tube, are proportionately shorter than those of the other Zeltnera species in the flora area. The four-merous corollas are useful in identifying very small plants of this species. The small corolla lobes are useful in distinguishing Z. exaltata from Z. multicaulis, which likewise has long pedicels but corolla lobes nearly as long as the tube.

In Nevada and adjacent regions of California, Zeltnera exaltata appears to intergrade with Z. namophila. As these species differ in chromosome number, additional chromosome counts and other techniques appropriate for the study of hybridization will be necessary for a satisfactory interpretation of apparent intermediates.

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

The inflorescence of Zeltnera trichantha is generally corymboid, but the level at which plants first branch varies. Plants branching at or near the base, so that the whole plant above ground is obconic, plants branching only in the upper fifth or less, and a complete range of intermediates may occur within a single population.

Unequivocal Zeltnera trichantha occurs in the Inner North Coast Range and San Francisco Bay region of California, from San Mateo and Stanislaus counties north to Tehama County, often on alkaline flats and in serpentine soils. This species can generally be recognized by a distinctive combination of relatively dense, obconic inflorescences; all flowers sessile or on true pedicels usually less than 4 mm, rarely to 6 mm; narrow, acute to acuminate corolla lobes, notably contrasting with the obtuse or abruptly acute corolla-lobe apices prevalent among the other Zeltnera species in the flora area; styles that are longer and more slender than those of most Zeltnera species, often extending 6–11 mm beyond the throat of the corolla; and cuneate stigmas 0.2–0.3 mm wide at the summit, which remain more or less appressed to each other throughout much of the life of the flower. Basal leaves are absent at flowering time. Usually, but less consistently, the cauline leaves are elliptic, widest near the middle, tapering toward the base, and acute to acuminate at the apex. Elsewhere in California, plants of Z. venusta with narrow corolla lobes often resemble Z. trichantha to various degrees. These species are contrasted in the discussion of Z. venusta. Other species, notably Z. muehlenbergii, occasionally approach Z. trichantha in habit, but, like Z. venusta, differ in having two distinctly separate, fan-shaped stigmas on a shallowly cleft style.

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