THE PHYTOGEOGRAPHY OF EUROPEAN AND MEDITERRANEAN HEATH SPECIES (ERICOIDEAE, ERICACEAE) - A QUANTITATIVE-ANALYSIS

The geographic ranges of heath species in Europe and the Mediterranean and their relationships with environmental (climatic and ecogeographi c) variables and biological features are analysed by means of multivar iate methods. In particular, TWINSPAN classifications into floristic e lements and floristic regions, DCA floristic ordinations, CCA environm ent-constrained ordinations and CCA biology-constrained ordinations ar e carried out. Results of the analyses show a correspondence with conv entional regionalization analyses based on broader criteria, and less correspondence with numerical analyses of other taxonomic groups at a similar scale. This lack of fit depends on the particular history and ecology of the taxonomic groups under study. A number of climatic (tem perature and water stress) and geographic (coast length) variables are associated with different types of heaths according to their geograph ical ranges (continental, Mediterranean, Atlantic). Biological feature s of heaths account for a small part of the variation in range, but th e association of temperate heaths with a preference for acid soils, of Mediterranean heaths with pubescence, and of Atlantic heaths with pla nt height is of interest. Heath species richness throughout Europe and the Mediterranean is analysed by multiple regression analyses and, ap art from a strong influence of area size, a significant effect of wate r conditions, temperature and proximity to sea is detected. The area w ith the highest heath species richness is Western Mediterranean. Addit ional classification, ordination and multiple regression analyses of h eaths in the Iberian Peninsula (Spain and Portugal, the areas with the highest heath diversity) revealed similar patterns to those found in Europe and the Mediterranean. The effect of heterogeneity of the studi ed units at this latter scale is removed in the Iberian analysis becau se of the relative homogeneity of the units considered at this scale.