Fagaceae

The Fagaceae are a family of flowering plants that includes beeches, chestnuts and oaks, and comprises eight genera with about 927 species. Fagaceae in temperate regions are mostly deciduous, whereas in the tropics, many species occur as evergreen trees and shrubs. They 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. Their leaves are often lobed and both petioles and stipules are generally present. 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 (usually containing one seed) 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 are one of the most significant sources of wildlife food.

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 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. Nuts of some species in the Asian tropical genera '' Castanopsis'' and '' Lithocarpus'' are edible and often used as ornamentals.

Classification

The Fagaceae are often divided into five or six subfamilies and are generally accepted to include 8 (to 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.

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'' (D. Don) 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 009/small>—Tanoaks; 1 species (formerly '' Lithocarpus densiflorus''), endemic to California and southwest Oregon
**''Quercus'' L. 1753—oaks; about 600 species, widespread Northern Hemisphere, crossing the equator in Indonesia
**'' Trigonobalanus'' Forman 1962—three species, tropical southeast Asia, Northern South America ( Colombia) (three species of ''Colombobalanus'' and ''Formanodendron'' are included)

The ''Quercus'' subgenus ''Cyclobalanopsis'' is treated as a distinct genus by th
''Flora of China''
but as a subgenus by most taxonomists.

The genus '' Nothofagus'' (southern beeches; about 40 species from the Southern Hemisphere), 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 (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. In tropical Southeast Asia, more than 400 species of '' Castanopsis'' and '' Lithocarpus'' are occur, with some species performing similar dominant roles over large areas.

Systematics

Modern molecular phylogenetics suggest the following relationships:

Images

File:Fagaceae_Interior_live_oak_quercus_wislizenii_var_wislizenii.jpg, Flowering, 2018
File:Fagaceae_Scruboak_Quercus_berberidifolia.jpg, Acorns, 2018

References

External links

Fagaceae in Topwalks
- diagnostic photos of many species at The Morton Arboretum

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Rosid families