**1. Introduction**

Mediterranean arborescent scrubs with *Ziziphus* Mill. species have been coded as habitat 5220\* (arborescent matorral with *Ziziphus*) and included in the Habitats Directive of the European Commission since 1992 [1], which lists Europe's most endangered and vulnerable habitats. These plant communities, recognized in the Iberian Southeast, Cyprus, Sicily, and surrounding islands, are composed mainly by pre-desert deciduous scrub with *Ziziphus lotus* (L.) Lam. or *Gymnosporia senegalensis* (Lam.) Loes. [=*Maytenus senegalensis* (Lam.) Exell; =*Maytenus senegalensis* subsp. *europaeus* (Boiss.) Rivas Mart. ex Güemes & M.B. Crespo] and smaller specimens of *Periploca laevigata* Aiton subsp. *angustifolia* (Labill.) Markgraf, *Lycium intricatum* Boiss., *Asparagus horridus* L., *A. albus* L., *Withania frutescens* (Sims) Sweet, etc. The largest patches of these communities are distributed in the arid Iberian southeast under a xerophytic

thermomediterranean bioclimate and correspond to the mature phase or climax of the climatophilous and edapho-xero-psammophilous vegetation series [2–4].

The Mediterranean Basin, and specifically the eastern region of Andalucia (Spain) and some islands as Sicily (Italy), accumulates a group of environmental conditions which result in the existence of these variety of habitats that have given shelter to paleoendemic species and favored specialization processes [5, 6]. This habitat, which is represented by the communities of arborescent scrub with *Ziziphus*, forms the type of vegetation that can produce the maximum of biomass in relation to the prevailing climatic conditions. These conditions include an arid and warm summer, typical of the Mediterranean climate, with low or no water availability for plants. In addition, the arrangement of this type of vegetation in hemispherical clusters is very impressive from the landscape point of view, and it has elicited various interpretations about the community dynamics [7].
