Indicator species and floristic patterns in different forest formations in southern Atlantic rainforests of Brazil

One of the greatest concerns in community ecology is to find how species composition patterns are related to different environmental and spatial conditions. This approach is especially interesting when applied to high diversity heterogeneous forests such as the Brazilian Atlantic Rainforest sensu lato. The present study aims to verify the existence of indicator species in four southern Atlantic Rainforest formations and identify relationships among distributions of tree species with environmental and spatial variables. For that, tree species density data of 21 phytosociological surveys were collected from the literature. The data were analyzed using indicator species and partial canonical redundancy analysis (partial RDA). Sandy coastal formation contained the greatest number of indicator species (17), followed by Atlantic rainforest (10), cloud forest (4) and Araucaria forest (3). The partial RDA analysis explained 22% of total data variation, of which 11% was assigned to the environment, 5% to space, 6% to spatial component of environmental influence, and 78% remained undetermined. The forest formations present different sets of indicator species suggesting replacement of species along the forest formations. The largest and significant fraction of variation in the composition and abundance of tree species explained by environmental variables reflects the heterogeneity and complexity of habitats throughout the region of Atlantic Forest. The low spatial influence and the environmental results indicate a pattern of structured communities due to different requirements of niches by species (niche theory)