Peninsular patterns of breeding landbird richness in Italy: On the role of climatic, orographic and vegetational factors

Battisti C., Testi A.

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In this study, an analysis of the breeding landbird distribution patterns in the Italian peninsula in relation to climatic, orographic, and indirectly, to vegetational factors has been carried out. Data were drawn from the Atlas of Breeding Birds in Italy (Meschini and Frugis, 1993) and arranged in latitudinal bands (LB). Three matrices (species/latitude, species/classes of LB with same bioclimatic Mediterranean area, species/ classes of LB with same altitudinal ranges) were obtained and analyzed with multivariate statistics. Comparations with thematic maps at national scale highlight that differences in the species richness among LB are localized in corrispondence with orographic, bioclimatic, geobotanic, anthropic discontinuities along the peninsula. Results, interpreting the preceding hypotheses on latitudinal changes of species richness, have evidenced that fauna changes occur at bioclimatic and orographic thresholds. These changes are due, in part, to quantitative differences in the number of species among the latitudinal bands, and in part to qualitative differences which will be investigated in successive works. Floristic and physiognomic-structural changes of vegetation probably contribute, indirectly, to these. Climate at macroscale level, orography and vegetation at mesoscale level, may influence the observed patterns. Thus, a primary role of physical factors and a secondary role of biological ones, is confirmed in determining the breeding landbird richness patterns in peninsular Italy.