A NUMERICAL-ANALYSIS OF THE DISTRIBUTION PATTERNS OF SALIX L SPECIES IN EUROPE

This paper aims to explore how well numerical techniques that are commonly used at ecological scales, perform at broad biogeographical scales in detecting and explaining major distributional patterns of species within the genus Salix at the European continental scale. The occurrences of the sixty-five native Salix species in 484 grid squares comprising Europe, were recorded on the basis of distributional maps in Atlas Florae Europaeae. Distributional patterns were described numerically by means of two-way indicator species analysis and detrended correspondence analysis, and were related numerically to thirteen climatic and geographic variables recorded for each of the 484 grid squares by means of simple discriminant functions and canonical correspondence analysis. Regional climate, mainly related to summer temperature, largely accounts for the major distributional patterns of Salix in Europe. The number of species in each grid was related numerically to the same thirteen climatic and geographic variables. Area, regional climatic variability, and latitude were the most important predictors for the broad-scale diversity within Salix. An attempt was made to relate the distributional patterns to the habitat preferences and morphology of each species. The results suggest that some distributional types can be related to species occurrences in certain habitats and altitudes, possibly because of the temperature tolerances of these species.