Quercus parvula
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Q. parvula
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| Binomial name | |
| Quercus parvula Greene
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Quercus parvula is an evergreen red oak (Section Lobatae) found on north-facing Santa Cruz Island slopes and in the California Coast Ranges from Santa Barbara County north to Mendocino County. It was taxonomically combined with Quercus wislizeni until resurrected as a separate species by Kevin Nixon in 1980.[1] The type locality is Palo Colorado Canyon in Monterey County.
Three varieties of Q. parvula are currently recognized:[2]
- Q. parvula var. parvula,[3] Santa Cruz Island oak[2] - Santa Cruz Island, California
- Q. parvula var. shrevei,[1][4] Shreve oak[2] or forest oak[5] - central and northern coastal California
- Q. parvula var. tamalpaisensis, Tamalpais oak[6] - Marin County, California
Q. parvula differs morphologically from its close relative Q. wislizeni in the following ways:[7]
- Leaf blades are larger, > (2)4 cm long rather than < 4(6) cm
- Leaf blades are thinner, generally < 0.26 mm near the apex rather than usually > 0.26 mm
- Current year twigs are 5-sided rather than ± roundish in cross section
- Leaf petioles and current year twigs are glabrous to sparsely hairy rather than moderately to very hairy
- Nut tips are blunt rather than more sharply pointed
- Abaxial golden glandular uniseriate leaf blade trichomes are missing or sparse rather than moderate to dense
- Abaxial multiradiate leaf blade trichomes are missing or sparse on the midvein rather than occasional to common
- Secondary leaf blade veins are raised abaxially rather than ± not raised
Q. parvula and Q. wislizeni never produce newly emerging leaves with a velvety coating of red uniseriate trichomes on the abaxial (upper) surface. This separates them from Q. kelloggii and both varieties of Q. agrifolia which produce such leaves.
Ecology
Mainland Q. parvula is commonly found with or near Sequoia sempervirens (coast redwood), and often near Quercus agrifolia var. agrifolia (coast live oak) and Notholithocarpus densiflorus (tanoak).
Q. parvula differs ecologically from Q. wislizeni in the following ways:[7]
- Island or coastal habitat rather than Sierra foothills
- Associates with Sequoia sempervirens rather than Pinus sabiniana
Hybridization
Quercus parvula is theoretically capable of hybridizing with all of the other California red oaks except the higher elevation southern California Quercus agrifolia var. oxyadenia[8] (sharpacorn oak[9]) from which it is separated by the Transverse Ranges. However Q. parvula's generally later flowering time (April–May versus February–April for Q. kelloggii, Q.wislizeni and Q. agrifolia) may limit genetic exchange with other Lobatae.
DNA studies currently in progress may show that Tamalpais oak is an intermediate form between Q. parvula and Q. kelloggii and may also more clearly define the relationship between the other two varieties of Q. parvula.
References
- ↑ 1.0 1.1 K. Nixon, "A Systematic Study of Quercus parvula Greene on Santa Cruz Island and Mainland California," Master's Thesis, 1980.
- ↑ 2.0 2.1 2.2 Jepson Flora Project (eds.) 2015 Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html July 17, 2015
- ↑ Greene, Pittonia 1:40 (1887)
- ↑ K. Nixon, C.H. Muller, “New Names in California Oaks,” Novon 4(4):391 (1994)
- ↑ R. Morgan et al, in Santa Cruz Cnty. Pl. Checklst., 22 (2005)
- ↑ S.K. Langer, “A New Oak On Mount Tamalpais,” Four Seasons, 9(3): 21-30 (1993)
- ↑ 7.0 7.1 Keuter, "Key to the California Lobatae," ined (2016)
- ↑ Torr., Sitgr. Rep., 172, pl. 17 (1853)
- ↑ J.G. Cooper, Smithsonian Rep. 1858: 261 (1859)
