Quercus pacifica

Nixon & C. H. Muller

Novon 4: 391. 1994.

Conservation concernEndemicIllustrated
Synonyms: Quercus dumosa var. polycarpa Greene
Treatment appears in FNA Volume 3.

Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. Bark scaly on older branches and trunk. Twigs brownish or reddish, minutely puberulent, becoming glabrate and gray with age. Buds light or chestnut-brown, ovate or globose, 2-3 × 1-2 mm. Leaves: petiole 2-5 mm. Leaf-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. 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. Cotyledons distinct.


Phenology: Flowering spring.
Habitat: Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands
Elevation: 0-300 m

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.

Selected References

None.

Lower Taxa

None.
... more about "Quercus pacifica"
pedunculate +  and subsessile +
Acute (?) +, Subacute (?) +, Rounded (?) +  and Blunt (?) +
Kevin C. Nixon +
Nixon & C. H. Muller +
black;brown;black;brown;gray;white +
attenuate-decurrent;rounded;cuneate +
chestnut-brown +  and light +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
Globose (?) +  and Ovate (?) +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
2-6-lobed +
pistillate +, capitate +  and spicate +
starchy +  and fleshy +
hemispheric +  and turbinate +
0 cm0 mm <br />0 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
multibracteate +, spiny +  and scaly +
0-300 m +
pistillate +  and staminate +
biennial +, annual +  and maturation +
1-seeded +  and winged +
in groups +  and enclosed +
Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands +
minute +
pistillate +, spicate +  and staminate +
tomentulose +  and glabrate +
2 cm20 mm <br />0.02 m <br /> (4 cm40 mm <br />0.04 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (2 cm20 mm <br />0.02 m <br />) +
arranged +  and alternate +
with 1-5 irregular teeth +  and entire +
toothed +  and entire +
1,500 cm15,000 mm <br />15 m <br /> (2,000 cm20,000 mm <br />20 m <br />) +
600 cm6,000 mm <br />6 m <br /> (900 cm9,000 mm <br />9 m <br />) +
light-brown +
2,000 cm20,000 mm <br />20 m <br /> (3,000 cm30,000 mm <br />30 m <br />) +
1/4 +  and 1/2 +
tapered +, fusiform +  and acute-cylindric +
900 cm9,000 mm <br />9 m <br /> (1,500 cm15,000 mm <br />15 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
Flowering spring. +
connate +  and distinct +
few-to-many +
tuberculate +
reduced +
anastomosing +, branching +  and unbranched +
Conservation concern +, Endemic +  and Illustrated +
inconspicuous +
distinct +
subulate +  and dilated +
enlarged +
with minute , scattered , stellate hairs +  and glabrate +
Quercus dumosa var. polycarpa +
Quercus pacifica +
Quercus sect. Quercus +
species +
spheric +  and ovoid terete or angled +
mucronate +
bristle-tipped +
gray +, reddish +  and brownish +
glabrate +  and puberulent +
tree +  and shrub +