Floristic similarity of lycophytes and ferns in the Amazonia/Cerrado transition zone in the central region of northern Maranhão state, Brazil

Floristic similarity studies make it possible to compare species richness between different phytophysiognomies and to assess whether species are typical of a phytophysiognomies or if they are common to two or more phytophysiognomies. The Immediate Geographic Region of São Luís (IGR), in the central region of northern Maranhão, is characterized by the presence of Amazonia, Cerrado, and coastal vegetation phytophysiognomies. The objectives of this work were to verify if the fern and lycophyte species in the IGR are similar to those in another Amazonia and Cerrado phytophysiognomies in Maranhão and Brazil. Sixty-three species of lycophytes and ferns were identified, with a predominance of individuals in the families Pteridaceae and Polypodiaceae. A similarity analysis indicated the study area has a greater affinity with the Amazonia. This is the first floristic similarity study that emphasizes ferns and lycophytes in Maranhão. However, the scarcity of floristic surveys in Maranhão and other ecotonal areas in Brazil hindered a more complex analysis of the floristic similarity of these phytophysiognomies.