Contribution to the Knowledge of Rocky Plant Communities of the Southwest Iberian Peninsula.

The rocky habitats of southern Portugal are ecosystems with extreme xericity conditions, associated with special abiotic strains. In these unstable ecological conditions, a considerable diversity of plant communities occurs. The objective of this study, carried out in the Algarve and Monchique, and the Mariánica Range biogeographical sectors, is to compare chasmo-chomophytic communities of the southwestern Iberian Peninsula, using a phytosociological approach (Braun-Blanquet methodology) and numerical analysis (hierarchical cluster analysis). From these results, two new communities were identified, and , as a result of floristic and biogeographical differences from other associations already described within the alliances and , both included in the class.