ABSTRACT
Leguminosae is the most diverse family in the caatinga based on the number of species. These species show distinct patterns of geographic distribution, allowing the infererence of floristic relationships between different areas. This paper presents a floristic survey of the Leguminosae in the caatinga at Tucano in order to assess floristic similarity with other areas of the Brazilian semi-arid. Eleven fieldtrips to nine caatinga sites were carried out from 2004 to 2006. Similarity analysis of 24 caatinga areas was performed using Sørensen's index and UPGMA clustering. The survey identified 74 species belonging to 41 genera. Despite closer proximity of the caatinga areas studied in Tucano, these areas were not grouped together in the cluster analysis. They were grouped with other areas of caatinga growing on similar substrate. These results highlight the importance of a local scale in phytogeographical studies and support the hypothesis that semi-arid vegetation includes two distinct biotas, one related to sedimentary sand surfaces, the other on soils derived from the crystalline rock shield.
Key words:
Biogeography; dry forests; floristic similarity