|Holm oak (Quercus ilex subsp. rotundifolia)|
The family Fagaceae, or beech family, comprises about 600 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like (cupule) nuts. Fagaceous leaves are often lobed and both petioles and stipules are generally present. Fruits lack endosperm and lie in a scaly or spiny husk that may or may not enclose the entire nut, which may consist of one to seven seeds. The best-known group of this family is the oaks, genus Quercus, the fruit of which is a non-valved nut (usually containing one seed) called an acorn. The husk of the acorn in most oaks only forms a cup in which the nut sits.
Several members of the Fagaceae have important economic uses. Many species of oak, chestnut, and beech (genera Quercus, Castanea, and Fagus, respectively) are commonly used as timber for floors, furniture, cabinets, and wine barrels. Cork for stopping wine bottles and a myriad of other uses is made from the bark of cork oak, Quercus suber. Chestnuts, a tasty treat enjoyed by many in the winter, are the fruits from species of the genus Castanea. Numerous species from several genera are prominent ornamentals, and wood chips from the genus Fagus are often used in flavoring beers.
The Fagaceae are often divided into five or six subfamilies and are generally accepted to include 9 or 10 genera (listed below). Monophyly of the Fagaceae is strongly supported by both morphological (especially fruit morphology) and molecular data.
The Southern Hemisphere genus Nothofagus, commonly the southern beeches, was historically placed in the Fagaceae sister to the genus Fagus, but recent molecular evidence suggests otherwise. While Nothofagus shares a number of common characteristics with the Fagaceae, such as cupule fruit structure, it differs significantly in a number of ways, including distinct stipule and pollen morphology, as well as having a different number of chromosomes. The currently accepted view by systematic botanists is to place Nothofagus in its own family, Nothofagaceae.
- Castanea - chestnuts; eight species, north temperate east Asia, southwest Asia, southeast Europe, eastern North America
- Castanopsis - chinquapins or chinkapins about 125-130 species, southeast Asia
- Chrysolepis - golden chinkapins; two species, western USA
- Colombobalanus - one species C. excelsa, northern South America, often included in Trigonobalanus
- Fagus - beeches; 50 species, north temperate east Asia, southwest Asia, Europe, eastern North America
- Formanodendron - one species F. doichangensis, southeast Asia, often included in Trigonobalanus
- Lithocarpus - stone oaks; about 330-340 species, warm temperate to tropical Asia
- Notholithocarpus - Tanoaks; 1 species (formerly Lithocarpus densiflorus, endemic to California and southwest Oregon
- Quercus - oaks; about 900 species, widespread Northern Hemisphere, crossing the equator in Indonesia
- Trigonobalanus - one species T. verticillata, tropical southeast Asia (three species if Colombobalanus and Formanodendron are included)
The Quercus subgenus Cyclobalanopsis is treated as a distinct genus by the Flora of China, but as a subgenus by most taxonomists.
The Fagaceae are widely distributed across the Northern Hemisphere. Genus-level diversity is concentrated in Southeast Asia, where most of the extant genera are thought to have evolved before migrating to Europe and North America (via the Bering Land Bridge). Members of the Fagaceae (such as Fagus grandifolia, Castanea dentata and Quercus alba in the Northeastern United States, or Fagus sylvatica, Quercus robur and Q. petraea in Europe) are often ecologically dominant in northern temperate forests.
- Judd, Walter S., Christopher S. Campbell, Elizabeth A. Kellogg, Peter F. Stevens, Michael J. Donoghue. Plant Systematics: A Phylogenetic Approach Third Edition. Sinauer Associates, inc. Sunderland, MA 2008.
- Cronquist, Arthur. An Integrated System of Classification of Flowering Plants. Columbia University Press: New York, NY 1981.
- Takhtajan, Armen. Diversity and Classification of Flowering Plants. Columbia University Press, New York 1997.
- Manos, PS., AM Stanford. 2001b The historical biogeography of Fagaceae: Tracking the tertiary history of temperate and subtropical forests of the Northern Hemisphere. International Journal of Plant Sciences 162: S77-S93 Suppl. 6.