Areas of endemism are the smallest units of biogeographical analysis. One of its definitions is that these areas harbor organisms with restricted distributions caused by non random historical factors. The aim of this study was to examine historical relationships among areas of endemism in the Neotropics using Brooks Parsimony Analysis (BPA). We applied BPA to 12 unrelated taxa distributed within two sets of endemic areas in order to: (1) compare the proposed endemic area classifications; (2) examine whether Amazonia and Atlantic Forest are true biogeographic units and, (3) examine whether the inclusion of open area formations influence area relationships of the surrounding forests. General area cladograms revealed a basal split between Amazonian and Atlantic forests, suggesting that these areas have been isolated for a long period of time. All Atlantic forest endemic areas formed a monophyletic cluster, showing a sequence of vicariant events from north to south. The hypothesis that Amazonia is a composite area, made up of different historical units, is herein corroborated. When Cerrado and Caatinga (grasslands and savannas) are included, internal area relationships within Amazonia change, indicating that area classification schemes comprising forests and open formations should be preferred given the complementary history of these areas.
area classification; area relationships; historical biogeography; Neotropical region
