Quercus pacifica |
Quercus hinckleyi |
|
---|---|---|
Channel Island scrub oak, island scrub oak, Pacific oak |
Hinckley oak |
|
Habit | Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. | Shrubs, evergreen, low, to 0.75(-1.5) m, spreading rhizomatously in thickets, intricately branched. |
Bark | scaly on older branches and trunk. |
gray, scaly. |
Twigs | brownish or reddish, minutely puberulent, becoming glabrate and gray with age. |
light brown, pruinose, becoming waxy-glaucous in 2d season, 1-1.5 mm diam., glabrous or sparsely and minutely stellate-pubescent. |
Buds | light or chestnut brown, ovate or globose, 2-3 × 1-2 mm. |
minute, subrotund, 0.5-1 mm; scales reddish brown, glabrous except for ciliate margins. |
Leaves | blade obovate or oblong, planar to moderately convex or undulate, 15-40 × 7-20(-40) mm, base cuneate or rounded, attenuate-decurrent along petiole, margins minutely cartilaginous, entire or with 1-5 irregular teeth on each side, secondary veins obscure, 1-5 on each side, apex blunt or rounded, occasionally subacute with mucronate tip; surfaces abaxially waxy, glandular, with scattered minute, flat, appressed, ± 8-rayed stellate hairs, not obscuring surface, adaxially green, glossy, glabrate or with minute, scattered, stellate hairs. |
blade subrotund or rotund, to 15 × 15 mm, thick, leathery, base cordate or auriculate, margins strongly crisped with 2-3 coarse, spinescent teeth on each side, cartilaginous-thickened secondary veins obscure, apex acute or obtuse, spine-tipped; surfaces abaxially blue-green, glaucous, glabrous, microscopically markedly papillose, adaxially blue-green, glaucous, glabrous, secondary veins slightly raised on both surfaces. |
Acorns | paired or solitary in leaf axil, subsessile, rarely pedunculate in teratological forms; cup hemispheric to turbinate, to 15 mm deep × 20 mm wide, enclosing only 1/4-1/2 nut, scales moderately to heavily tuberculate, irregularly formed; nut light brown, acute-cylindric or fusiform, tapered, (15-)20-30 × (6-)9-15 m, apex acute, glabrate. |
solitary, subsessile or on axillary peduncle to 4 mm; cup shallow, saucer-shaped, 1-3 mm deep × 10-15 mm wide, enclosing base of nut only, margin irregularly undulate, scales closely appressed, minute, basally tuberculate-thickened, glabrous except for thin ciliate margins; nut ovoid, 10-20 × 8-12 mm, glabrous. |
Cotyledons | distinct. |
distinct. |
Quercus pacifica |
Quercus hinckleyi |
|
Phenology | Flowering spring. | Flowering spring. |
Habitat | Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands | On dry desert slopes |
Elevation | 0-300 m (0-1000 ft) | 1150-1400 m (3800-4600 ft) |
Distribution |
CA
|
TX; Mexico |
Discussion | Of conservation concern. Quercus pacifica is endemic on three of the California Channel Islands: Santa Cruz, Santa Catalina, and Santa Rosa. It is not known from the mainland, but it bears a superficial similarity to some of the tree forms that are putative hybrids between Q. engelmannii and Q. cornelius-mulleri in San Diego County. The latter populations, sometimes treated as Q. ×acutidens, differ in having much greater variability in leaf shape; thicker, more leathery leaves; denser abaxial leaf vestiture; much smaller hairs, having more than 10 rays; and variable levels of connation of cotyledons (always distinct in Q. pacifica). Quercus pacifica appears to be most closely related to Q. douglasii, whether by direct descent or by introgression with another species no longer extant on the islands. Quercus ×macdonaldii Greene (as a species) [= Quercus dumosa var. macdonaldii (Greene) Jepson] is a stabilized hybrid complex between Quercus pacifica and Q. lobata Née. The plants tend to be small to moderate trees with leaves that resemble those of Q. lobata; the leaves are much more shallowly lobed and always less than two-thirds the distance from the margin to the midrib. Quercus ×macdonaldii is known from Santa Rosa, Santa Cruz, and Santa Catalina islands. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. This species is known only from two sites in the United States, El Solitario and near Shafter, Texas. The Shafter population includes some individuals with characteristics that suggest hybridization with Quercus pungens Liebmann. These plants are larger, with more pubescent twigs and leaves, and hemispheric acorn cups to 10 mm deep. Such plants have recently been collected in adjacent Mexico. Fossil evidence from packrat middens indicates Q. hinckleyi probably had a broader distribution and was a dominant shrub between 19,000 and 9500 years ago. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Quercus | Fagaceae > Quercus > sect. Quercus |
Sibling taxa | ||
Synonyms | Q. dumosa var. polycarpa | |
Name authority | Nixon & C. H. Muller: Novon 4: 391. (1994) | C. H. Muller: Contr. Texas Res. Found., Bot. Stud. 1: 40. (1951) |
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