Metacommunity structure, additive partitioning and environmental drivers of woody plants diversity in the Brazilian Atlantic Forest

Aim: To assess the metacommunity structure of woody plants in the Atlantic Forest (AF), compare the structure across its different forest types and evaluate the contribution of multiple scales and environmental drivers for the total biodiversity, providing theoretical basis for efficient conservation of this important hotspot. Location: South America, Brazilian Atlantic Forest. Methods: We compiled the occurrence of 2,071 woody plants in 177 sites across the Brazilian AF. We assessed the elements of metacommunity structure (species coherence, turnover and boundary clumping) to identify which idealized structure (checker-board, nestedness, Clementsian, Gleasonian, evenly spaced or random) characterizes the AF and its forest types. We used the additive partition of diversity to determine the main spatial scales promoting biodiversity in the AF, that is local (within sites, alpha-diversity), regional (among sites in each forest type, beta 1) or geographical (between forest types, beta 2), and examined environmental variables driving the metacommunity of the AF and forest types using canonical ordinations. Results: The AF and its forest types presented positive coherence, negative turnover and large boundary clumping values which best-fit the nested subsets metacommunity structure with clumped species loss. The diversity within sites (alpha-diversity) and among types (beta 2) was higher than expected by chance. The climatic gradient driving the species composition differed in the AF. Temperature variation affected the entire AF, particularly Dense and Seasonal forests, whereas precipitation affected mostly the Mixed forest. Main conclusions: Despite the similar structure underlying AF metacommunities, the main environmental gradient in each forest differs, highlighting ecological differences among communities at geographical scale. These differences are determinant for the high levels of biodiversity found in the AF. Conservation efforts should encompass all the AF ecosystems, considering its unique characteristics and prioritizing species-rich sites given that they adequately represent the regional species pool.