Diversity distribution and floristic differentiation of the coastal lowland vegetation: implications for the conservation of the Brazilian Atlantic Forest

Floristic differentiation and vegetation definition is an important step to recognize biome distribution and for biodiversity conservation. Here, we aim to verify if the distribution of the costal lowland vegetation in Brazilian littoral is congruent with climatic gradient and the previous vegetation definitions. Additionally we discussed the importance of terms for the Atlantic Forest conservation. Our study was based on floristic and geoclimatic data from 58 published surveys. We generate a checklist of 1088 woody species and verified species distribution according to environmental gradient using a Detrended Correspondence Analysis (DCA). We compared DCA's groups with the a priori vegetation definition and generate an a posteriori classification using TWINSPAN. DCA and TWINSPAN resulted in groups determined mainly by rainfall (r = -0.65) and soil sandiness (r = -0.71). Those groups were not congruent with both the previous vegetation definitions. The coastal lowland vegetation comprises two distinctive floristic groups representing forests and scrubs that occur in wetter climates (Ombrophilous lowland forests) in the Brazilian states of Santa Catarina, Parana and Sao Paulo and in drier climates of Espirito Santo, Rio de Janeiro (Restinga-Northern group) and Rio Grande do Sul (Restinga-Southern group) states. The floristic and historical relationships between Ombrophylous lowland forests and Restingas suggest that conservation initiatives should be more conservative and treat collectively all coastal lowland vegetation as a biodiversity hotspot.