Quercus ilex L. (holm oak) is a dominant tree within the Mediterranean basin and is used as a bioindicator of Mediterranean-type ecosystems (Plieninger et al., 2004; distribution map for Q. ilex see http://www.discoverlife.org). Q. ilex is an evergreen tree which grows in four bioclimates (semiarid, subhumid, humid and perhumid) and is present in different soil types. It grows up to 25 m and has sclerophyllous, tomentose leaves with a shape ranging from round to longer leaves, with or without spines. It comprises two different subspecies: Q. ilex subsp. ilex and Q. ilex subsp. ballota (syn. Q. rotundifolia). In the Iberian Peninsula, its importance derives from its presence in the most widespread agroforestry system in Europe known as dehesa. Dehesas play a main role as an ecological, economical and social system. They are characterized by the rearing of livestock, the production of acorns for livestock feeding, firewood production and cereal cropping.