ABSTRACT
Email: elenac@iiag.csic.es; amvieitez@iiag.csic.es 2 Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA)
Finca El Encín, Apdo. 127, 28800, Alcalá de Henares, Madrid, Spain. Email: mariano.toribio@madrid.org * Corresponding author
The genus Quercus (oak), which belongs to the Fagaceae family, is native to the northern hemisphere and includes both deciduous and evergreen species. Taxonomic classifi cation of the genus is very diffi cult as it can be represented by an imprecise number of species: according to Kleinschmit (1993), the differences in these numbers can be partly explained by the defi nition of interspecifi c hybrids as separate species and the sub-division of ecological forms into species. The genus is subdivided into two subgenera: Quercus and Cyclobalanopsis. The former is further divided into four sections: Protobalanus, Cerris, Quercus (white oaks) and Rubrae (red oaks) (Ducousso and Bordacs 2004).
