FNA: Zeltnera davyi vs. Zeltnera

Phenology

Flowering spring–summer.

Habitat

Moist coastal bluffs, interdunal depressions, open woods, sometimes in ultramafic soils.

Elevation

0–1000 m. (0–3300 ft.)

Distribution

CA

[WildflowerSearch map]

North America; Mexico; Central America; South America; West Indies; temperate to tropical regions

[BONAP county map]

Discussion

The name Centaurium muehlenbergii has sometimes been misapplied to Zeltnera davyi, with true Z. muehlenbergii then being called C. floribundum (J. S. Pringle 2010b).

The distinctly keeled calyx lobes cause the calyces of Zeltnera davyi to appear greater in diameter than those of related species and ovoid to ellipsoid rather than nearly cylindric. The combination of this calyx morphology and the proportionately wide, relatively deeply pigmented corolla lobes (usually evident in herbarium specimens) gives the flowers of Z. davyi a distinctive aspect.

Zeltnera davyi and Z. muehlenbergii are sometimes similar in habit. Medium-sized plants of Z. davyi are usually several-stemmed from the base, whereas that pattern is much less common in Z. muehlenbergii. Zeltnera davyi usually differs from Z. muehlenbergii in the presence of elliptic to ovate leaves over 5 mm wide (except on the smallest plants) well into the inflorescence; consistently present pedicels 4–30 mm long; calyx lobes with keels proximally 0.3–0.6 mm wide; and ovate-elliptic corolla lobes 3–7 × 2–3 mm. In Z. muehlenbergii, elliptic to narrowly ovate leaves, when present, are usually limited to the proximal one-third or less of the plant, with the distal leaves being narrower, and the corolla lobes are elliptic-oblong, 2–7 × 1–2 mm (J. S. Pringle 2010b).

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

Species ca. 25 (14 in the flora).

Plant size varies greatly in Zeltnera species, especially in Z. venusta and others that sometimes grow in intermittently moist habitats such as the edges of vernal pools. Small, one- or two-flowered plants, some only 3–10 cm, do not exhibit the characters of branching pattern, basal-leaf numbers or persistence, leaf and flower size, pedicel length, and orientation of styles and stamens by which the species are usually distinguished. It is scarcely feasible to identify such plants strictly from their own morphology; their provenance and the identity of larger plants in the vicinity must be considered. Branching pattern appears also to be affected by the density of the surrounding vegetation.

Some Zeltnera species are primarily outbreeding. They have large, showy corollas with conspicuous, sharply defined eyes. The style is at first deflexed in one direction and the stamens in the opposite. Later, the style becomes erect, and the stamens become radially disposed and erect to incurved. In these species, the stigma or stigmas are borne on a slender style often as long as or longer than the ovary at anthesis and much exceeding the stamens, although the latter are also distinctly exserted. Style length may vary among the flowers on a single plant, although true heterostyly is not known to occur in the genus. Smaller, presumably autogamous flowers may be present along with larger flowers. Other species are primarily, although probably not obligately, autogamous. They have smaller, often less brightly colored corollas with poorly defined eyes. The styles are shorter and generally erect, and the filaments may be erect or incurved throughout the life of the flower. Zeltnera arizonica, Z. beyrichii, Z. calycosa, Z. maryanniana, Z. trichantha, and Z. venusta exhibit the floral syndrome associated with outbreeding; the other taxa in the flora area, to various degrees, exhibit the morphology associated with autogamy (C. R. Broome 1973).

G. Mansion and L. Zeltner (2004) divided Zeltnera informally into a Californian group including species 1 through 6, a Texan group including species 7 through 14, and a Mexican group represented in the flora area only by Z. nudicaulis. Within the respective species-groups, especially the Californian group, some of the species are poorly defined morphologically. Some species, especially Z. venusta, vary greatly in the size and shape of the corolla lobes as well as in habit and vegetative characters and may thus resemble other species. Hybridization, introgression, and allopolyploidy are believed to account for some of the variation that has made Zeltnera problematic taxonomically, although some variation suspected of being due to hybridization may merely represent variability within species. Some otherwise well-differentiated species tend to be more similar to each other in morphology where their ranges overlap; in such cases, similarity has been interpreted as being due more to convergent responses to selective pressures than to interspecific hybridization (C. R. Broome 1981). In some localities, populations of intermediates appear to be more or less stabilized. In the classification presented here, plants treated as or suspected of being hybrids and introgressants may be more numerous and more widely distributed than one would consider pragmatic. Nevertheless, this treatment seems to present a truer picture of the evolutionary situation than would the recognition of intermediates between sympatric species as additional species or subspecies. In California, intergradation has been reported to involve, in various combinations, Z. davyi, Z. exaltata, Z. muehlenbergii, Z. namophila, Z. trichantha, and Z. venusta. In Texas, Z. calycosa appears to hybridize with Z. beyrichii and Z. texensis.

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

Key

1. Stems and midveins of leaves and sepals scabridulous to papillate-puberulent.	Z. glandulifera
1. Stems, leaves, and calyces glabrous.	→ 2
2. Pedicels mostly 10–75 mm, all or most of them longer than closed corollas.	→ 3
3. Corolla 6.5–10(–12.5) mm, tube scarcely constricted above ovary; distal cauline leaf blades usually narrowly linear to filiform, less than 2 mm wide, occasionally lanceolate to ovate or elliptic, to 4 mm wide.	Z. nudicaulis
3. Corolla 9–20 mm, tube distinctly constricted above ovary; distal cauline leaf blades linear to lanceolate or ovate, mostly (1–)2–6(–9) mm wide.	→ 4
4. Flowers more than 3 per stem except on unusually small plants; corollas usually 4-merous, lobes ca. 1/2 as long as tube or less.	Z. exaltata
4. Flowers usually 1–3 per stem; corollas 5-merous, lobes more than 1/2 as long as tube.	Z. multicaulis
2. Pedicels 0–30(–60) mm, all or most of them shorter than closed corollas.	→ 5
5. Mid-stem and distal cauline leaf blades filiform to narrowly linear, narrowly lanceolate, or narrowly oblanceolate, most less than 2 mm wide and ± as wide as stem diam.	→ 6
6. Primary stems (except those of small plants) and larger branches with well-developed central axis, with dichasial branching if any only near summit and in lateral cymules.	Z. namophila
6. Branching largely or entirely dichasial, with a central flower at each fork, or distally monochasial.	→ 7
7. Basal leaves absent; corolla lobes 3–7 mm.	Z. texensis
7. Basal leaves or withered remains usually numerous and conspicuous at flowering; corolla lobes 7–16 mm.	→ 8
8. Primary stems 3–30; basal leaves generally green at flowering; corolla lobes ovate-elliptic.	Z. maryanniana
8. Primary stems 1, although often branching near base; basal leaves often withered or absent at flowering; corolla lobes narrowly oblong-lanceolate to linear.	Z. beyrichii
5. Mid-stem and distal cauline leaf blades linear to lanceolate or wider, most usually 2+ mm wide and/or distinctly wider than stem diam.	→ 9
9. Pedicels mostly less than 6 mm, distal flowers often sessile.	→ 10
10. Apices of corolla lobes acute to acuminate; stigmas 2, closely appressed and sometimes appearing as 1.	Z. trichantha
10. Apices of corolla lobes obtuse to subacute; stigmas 2, divergent.	Z. muehlenbergii
9. Pedicels (2–)4–30(–60) mm.	→ 11
11. Calyx lobes with distinct keels proximally 0.3–0.6 mm wide; corolla lobes 3–7 mm.	Z. davyi
11. Calyx lobes ± sharply ridged but not distinctly keeled; corolla lobes (5–)6–20 mm.	→ 12
12. Basal leaves usually numerous and green at flowering; stigmas 1, lobes tardily diverging.	Z. maryanniana
12. Basal leaves few, present or absent at flowering; stigmas 2, lobes ± divergent.	→ 13
13. Leaves usually cauline only; corolla lobes widening ± abruptly above base (except in forms with very narrow lobes), proportions variable.	Z. venusta
13. Basal leaves usually present at flowering; corolla lobes widening gradually above base, less than 1.5 times as wide distally as at base.	→ 14
14. Plants (4–)9–30 cm; primary stems usually 1; corollas 12–23 mm.	Z. calycosa
14. Plants (10–)20–50(–60) cm; stems often several from base; corollas (closed), (15–)18–25 mm.	Z. arizonica