Population structure of the endangered tree fern Cyathea praecincta (Cyatheaceae), endemic of the Brazilian Atlantic Forest

his study aimed to determine the population structure of Cyathea praecincta (Kunze) Domin in an Atlantic Forest fragment in Northeastern Brazil. Individuals of C. praecincta were recorded inside 1800 m2 of interior forest area. Caudex height was measured in order to classify specimens into length classes and relate this variable with fertility of individuals. Ninety-eight individuals were sampled, featuring a low population density (5.4 individuals per 100 m-2) when compared to other tree fern populations. The spatial distribution was clustered (Ia = 2.12; p = 0.0002) and the length class distribution followed an exponential or reverse J-shaped pattern. The high number of individuals classifi ed in the smaller length class (0 to 0.25 m) may be an indication that the studied population is under expansion. This endorses the need for conservation of the study area and for reducing the risk of local extinction by disturbances