Quercus pacifica |
Quercus carmenensis |
|
---|---|---|
Channel Island scrub oak, island scrub oak, Pacific oak |
Mexican oak |
|
Habit | Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. | Shrubs or trees, deciduous, shrubs 0.5-2 m, rhizomatous, trees (on better sites) to 12 m, trunk 0.75 m diam. |
Bark | scaly on older branches and trunk. |
light gray, checkered or furrowed. |
Twigs | brownish or reddish, minutely puberulent, becoming glabrate and gray with age. |
often strikingly red, 1-1.5 mm diam., sparingly (rarely densely) stellate-pubescent, somewhat glabrescent and gray 2d year. |
Buds | light or chestnut brown, ovate or globose, 2-3 × 1-2 mm. |
light brown, nearly round, 1-1.5 mm, indumentum similar to twigs. |
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 obovate or narrowly obovate, (20-)30-50 × 10-30 mm, thin to moderately leathery, base cuneate to rounded, margins shallowly and irregularly lobed or coarsely toothed in distal 1/2, rarely subentire, teeth mucronate, secondary veins 9-12 on each side, branching or passing directly to teeth, apex acute, sometimes broadly rounded; surfaces abaxially light green or yellow-green, prominently pubescent with minute, erect velvety hairs, adaxially surfaces dark green, sparsely and minutely stellate-pubescent. |
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 or paired, subsessile or short-pedunculate (immature); cup (mature) unknown; scales (immature) light brown, tip acute, canescent. |
Cotyledons | distinct. |
unknown. |
Nut | unknown. |
|
Quercus pacifica |
Quercus carmenensis |
|
Phenology | Flowering spring. | |
Habitat | Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands | Shrublands and woodlands on limestone |
Elevation | 0-300 m (0-1000 ft) | 2200-2500 m (7200-8200 ft) |
Distribution |
CA
|
TX; Mexico (Coahuila) |
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. Shrublands and woodlands on limestone; of conservation concern; 2200-2500 m; Tex.; Mexico (Coahuila). Quercus carmenensis is known in the United States from only one collection from the Chisos Mountains, Texas; otherwise, it is known in the Sierra del Carmen region, Coahuila, Mexico. (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: Amer. Midl. Naturalist 18: 847. (1937) |
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