Fagaceae is a family of flowering plants that includes beeches and oaks, and comprises eight genera with about 927 species. The Fagaceae are deciduous or evergreen trees and shrubs, characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like nuts. Their leaves are often lobed and both petioles and stipules are generally present. Leaf characteristics of Fagaceae can be very similar to those of Rosaceae and other rose motif families. Their 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. In the oaks, genus Quercus, the fruit is a non-valved nut called an acorn. The husk of the acorn in most oaks only forms a cup in which the nut sits. Other members of the family have fully enclosed nuts. Fagaceae is one of the most ecologically important woody plant families in the Northern Hemisphere, as oaks form the backbone of temperate forest in North America, Europe, and Asia and one of the most significant sources of wildlife fodder. Several members of the Fagaceae have important economic uses. Many species of oak, chestnut, and beech are commonly used as timber for floors, furniture, cabinets, and wine barrels. Cork for stopping wine bottles and myriad other uses is made from the bark of cork oak, Quercus suber. Chestnuts 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.
Classification
The Fagaceae are often divided into five or six subfamilies and are generally accepted to include 8 genera. Monophyly of the Fagaceae is strongly supported by both morphological 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.
Subfamilies and genera
Fagoideae K. Koch
*Fagus L.—beeches; about 10 to 13 species, north temperate east Asia, southwest Asia, Europe, eastern North America
Quercoideae Õrsted
*Castanea Mill. 1754—chestnuts; eight species, north temperate east Asia, southwest Asia, southeast Europe, eastern North America
*Castanopsis Spach 1841—chinquapins or chinkapins; about 125–130 species, southeast Asia
*Chrysolepis Hjelmq. 1948—golden chinkapins; two species, western United States
*Lithocarpus Blume 1826—stone oaks; about 330-340 species, warm temperate to tropical Asia
*Notholithocarpus P. S. Manos, C. H. Cannon & S.H. Oh 2008 —Tanoaks; 1 species, endemic to California and southwest Oregon
*Trigonobalanus Forman 1962—one species T. verticillata, tropical southeast Asia
The Quercus subgenus Cyclobalanopsis is treated as a distinct genus by the , but as a subgenus by most taxonomists. The genus Nothofagus, formerly included in the Fagaceae, is now treated in the separate family Nothofagaceae.
Distribution
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. Members of the Fagaceae are often ecologically dominant in northern temperate forests.
