Neotropical Fagaceae

William Milliken

Royal Botanic Gardens, Kew, UK. 

Description

Large trees (occasionally treelets or shrubs) with alternate, simple, petiolate leaves with pinnate venation and scaly intrapetiolar stipules. The leaf margins are usually serrate or occasionally dentate, sometimes conspicuously so. Leaves are generally leathery in texture and range from glabrous to tomentose; hairs may be simple, stellate or branched; no obvious exudates or odours. Flowers are unisexual and actinomorphic with an inconspicuous, apetalous perianth divided into two whorls of three tepals or 4-6 connate lobes.  Male flowers borne on catkins, subtended by bracts, stamens (3-)6-12(-18); anthers basifixed and dehiscing via longitudinal slits. Female flowers solitary or borne on short spikes or capitula. Gynoecium syncarpous with 2-3 carpels (2-3 styles). Fruit a nut or triangular achene, partly enclosed or subtended by a cupule of variable form but generally spiny or scaly.

Notes on delimitation

  • The Fagaceae are placed in the Fagales by morphological and molecular studies, close to the Betulaceae, Ticodendraceae, Juglandaceae and Myricaceae.
  • The genus Nothofagus Blume does not occur in the tropical regions of the Americas and is not included in this description. 

Distribution in the Neotropics

  • Within the Neotropics, Fagus L. only occurs in Mexico and Colombobalanus Nixon & W.L.Crepet in Colombia, where it dominates some high-altitude forests.
  • Quercus L. is more widespread, ranging from Mexico to Brazil and Cuba (mainly at higher altitudes).

Distinguishing characters (always present)

  • Simple alternate leaves with pinnate venation, stipules, unisexual flowers with male flowers borne on catkins, fruits partially enveloped or subtended by a cupule.

Other important characters

  • Although stipules are always present, these often fall and may not therefore be easily detected.
  • The twigs of many species bear white lenticels.
  • Clustered subterminal buds, with obvious bud scales, are another common feature of the family.

Key differences from similar families

Fagaceae could be confused with some other members of the Fagales, but differ from them in possessing the folllowing characters:

Number of genera

Three genera occur in the Neotropics: Quercus, Fagus and Colombobalanus

  • Fagus is represented by one species only (F. mexicana Martínez - considered by some to be a variety of F. grandifolia Ehrh.), found in the high mountains of Mexico.
  • Colombobalanus (considered by some to be part of Trigonobalanus Forman) is also only represented by one species, C. excelsa (Lozano et al.) Nixon & Crepet, which occurs in Colombia.
  • Quercus is more diverse and more widely distributed, occurring throughout the Neotropics in upland forest.

Useful tips for generic identification

  • Fagus mexicana is distinguishable by its solitary, spiny, 4-valved cupule with triangular fruits, and the fact that it only occurs in the cloud forests of Eastern Mexico.
  • Quercus is easily recognizable in fruit by its typical acorn structure: a smooth rounded nut subtended or partly enclosed by a (generally scaly) cupule. It commonly bears stellate hairs on the leaf undersides.
  • Colombobalanus is distinguishable by its scaly valved cupule (number of valves usually = number of fruits + 1), and the fact that it only occurs in Colombian mid-elevation forests, where it is thought to be threatened by habitat destruction.

Status

  • Native in the Neotropics but at least one non-native species (Quercus suber L. - the cork oak) is cultivated.

General notes

  • Most representatives of this family are large trees, many of which are exploited for their high-quality timber.
  • The wood is also used for charcoal production, and the bark (Quercus) as a source of tannins for leather production. 
  • The fruits (Quercus) are sometimes used to feed livestock.

Important literature

Nixon, K.C. (1993). Infrageneric classification of Quercus L. (Fagaceae) and typification of sectional names.  Ann. Sci. For. 50 Suppl. 1: 25s-34s.

Nixon, K.C. (2006). Global and Neotropical distribution and diversity of Oak (genus Quercus) and Oak forests.  pp 3-13 in: M. Kappelle, ed, Ecology and Conservation of Neotropical Montane Oak Forests. Springer, Berlin.

Nixon, K.C. & Crepet, W.L. (1989). Trigonobalanus Forman (Fagaceae): taxonomic status and phylogenetic relationships, Amer. J. Bot. 76 (6) (1989), pp. 828-841.

Manos, P. S. & Steele, K. P. (1997). Phylogenetic analyses of 'higher' Hamamelididae based on plastid sequence data. Amer. J.Bot.84:1407-1419.

Nixon, K.C.  (2004). Fagaceae.  pp 156-158 in: Smith, N.A. et al. (eds), Flowering plants of the Neotropics. Princeton University Press, New Jersey.

How to cite

Milliken, W. (2009). Neotropical Fagaceae. In: Milliken, W., Klitgĺrd, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Fagaceae.htm.

Click images to enlarge


Fagus mexicana Martínez (Martínez s.n., Mexico) © William Milliken, RBG, Kew.



Fruit of Fagus mexicana Martínez (Martínez s.n., Mexico) © William Milliken, RBG, Kew.



Fruit and nutlet of Fagus mexicana Martínez (Martínez s.n., Mexico) © William Milliken, RBG, Kew.



Flower of Fagus mexicana Martínez (Martínez s.n., Mexico) © William Milliken, RBG, Kew.



Quercus peduncularis  Nee © William Milliken, RBG, Kew.



Fruit of Quercus peduncularis  Nee © William Milliken, RBG, Kew.



Fruit of Quercus corrugata Hooker (Guatemala) © William Milliken, RBG, Kew.



Quercus corrugata Hooker (Guatemala) © William Milliken, RBG, Kew.



Inflorescence of Quercus corrugata Hooker (Guatemala) © William Milliken, RBG, Kew.



Quercus hintoni E.F. Warburg (Hinton et al. 5193, Mexico) © William Milliken, RBG, Kew.



Male inflorescence of Quercus hintoni E.F. Warburg (Hinton et al. 5193, Mexico) © William Milliken, RBG, Kew.



Female inflorescence of Quercus hintoni E.F. Warburg (Hinton et al. 5193, Mexico) © William Milliken, RBG, Kew.



Quercus humboldtii Bonpl. (Zarucchi et al. 7293, Colombia) © William Milliken, RBG, Kew.



Female flowers of Quercus humboldtii Bonpl. (Zarucchi et al. 7293, Colombia) © William Milliken, RBG, Kew.



Fruit of Quercus humboldtii Bonpl. © William Milliken, RBG, Kew.



Colombobalanus excelsa (Lozano et al.) Nixon & Crepet (Henao s/n, Colombia) © William Milliken, RBG, Kew.



Leaf venation of Colombobalanus excelsa (Lozano et al.) Nixon and Crepet (Henao s/n, Colombia) © William Milliken, RBG, Kew.



Fruit of Colombobalanus excelsa (Lozano et al.) Nixon & Crepet (Henao s/n, Colombia) © William Milliken, RBG, Kew.