Quercus tomentella

Quercus tomentella, the island oak,[3] island live oak,[4] or Channel Island oak,[5] is an oak in the section Protobalanus. It is native to six islands: five of the Channel Islands of California and Guadalupe Island, part of Baja California.

"Island oak" redirects here. For other uses, see Island oak (disambiguation).

Quercus tomentella
island oak, Santa Rosa Island
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Fagaceae
Genus: Quercus
Subgenus: Quercus subg. Quercus
Section: Quercus sect. Protobalanus
Species:
Q. tomentella
Binomial name
Quercus tomentella
Natural range of Quercus tomentella
Synonyms[2]
List
  • Quercus chrysolepis subsp. tomentella (Engelm.) A.E.Murray
  • Quercus chrysolepis var. tomentella (Engelm.) A.E.Murray
  • Quercus tomentella var. conjungens Trel.
  • Quercus tomentella f. conjungens (Trel.) Trel.
Foliage

It is placed in Quercus section Protobalanus.[6]

Description

Island oak is a tree growing up to 20 metres (66 feet) in height.[5] The mature tree has a grayish to reddish brown trunk with scaly, furrowed bark.[3] The twigs are reddish and covered in woolly hairs. The leathery leaf blades are often concave and are an oblong lance shape or oval with pointed or rounded tips. The edges are smooth or toothed.[5] The upper surfaces are dark green and lightly hairy when new, losing the hairs over time. The undersides are gray-green and coated in woolly hairs, becoming less woolly with age.[3] They are usually 7 to 10 centimetres (2+3⁄4 to 4 inches) long, sometimes up to 12 cm (4+3⁄4 in). The acorn grows singly or in pairs. The cup has thick scales and woolly hairs and is up to 3 cm (1+1⁄8 in) wide. The nut is up to 3.5 cm with a rounded tip.[3][5]

Distribution and habitat

It is native to six islands: five of the Channel Islands of California (Anacapa Island, San Clemente Island, Santa Catalina Island, Santa Cruz Island, and Santa Rosa Island) and Guadalupe Island, part of the State of Baja California.[7]

This species is a relict. Though it is now limited to the islands, it was once widespread in mainland California, as evidenced by the many late Tertiary fossils of the species found there.[5] Recently, it was found that there was a high genetic variability across many of the Q. tomentella populations, but this variation was not evenly distributed.[8]

Ecology

Island oak hybridizes with canyon live oak (Quercus chrysolepis).[5]

Conservation

The island oak was listed as an endangered species by the International Union for Conservation of Nature.[1]

The species is threatened by overgrazing from nonnative ungulates. The most rapid declines have occurred on Guadalupe Island.[1] The trees there are apparently no longer reproducing.[9] Feral goats have been abundant on the island for at least 150 years. The animals have eliminated much of the native vegetation and caused extensive soil erosion. Fenced enclosures have been helpful in the early recovery of some of the local flora.[10]

References
  1. Beckman, E.; Jerome, D. (2017). "Quercus tomentella". IUCN Red List of Threatened Species. 2017: e.T30959A2799049. doi:10.2305/IUCN.UK.2017-2.RLTS.T30959A2799049.en. Retrieved 19 November 2021.
  2. "Quercus tomentella Engelm.". World Checklist of Selected Plant Families. Royal Botanic Gardens, Kew – via The Plant List. Note that this website has been superseded by World Flora Online
  3. Rosatti, Thomas J.; Tucker, John M. (2014). "Quercus tomentella". In Jepson Flora Project (ed.). Jepson eFlora. The Jepson Herbarium, University of California, Berkeley.
  4. USDA, NRCS (n.d.). "Quercus tomentella". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team.
  5. Nixon, Kevin C. (1997). "Quercus tomentella". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 3. New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  6. Denk, Thomas; Grimm, Guido W.; Manos, Paul S.; Deng, Min & Hipp, Andrew L. (2017). "Appendix 2.1: An updated infrageneric classification of the oaks" (xls). figshare. Retrieved 2023-02-18.
  7. "Quercus tomentella". Inventory of Rare and Endangered Plants. California Native Plant Society. 2013.
  8. Ashley, M.V., J. R. Backs, L. Kindsvater and S. T. Abraham. 2018. Genetic variation and structure in an endemic island oak, Quercus tomentella and mainland canyon oak, Quercus chrysolepis. International Journal of Plant Science 179
  9. de la Luz, J. L. L., et al. (2003). On the urgency of conservation on Guadalupe Island, Mexico: is it a lost paradise? Biodiversity and Conservation 12(5), 1073-82.
  10. Junak, S., et al. (2003). Esfuerzos recientes de conservación y apuntes sobre el estado actual de la flora de Isla Guadalupe, Baja California, México. (Spanish) Presentation at Taller sobre la Restauración y Conservación de Isla Guadalupe [Workshop on Restoration and Conservation of Guadalupe Island]. Instituto Nacional de Ecología, November 13–14, 2003. HTML abstract Archived August 19, 2007, at the Wayback Machine (English)
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