Community organization and phylogenetic structure of the tree component of a nebular forest fragment in planalto catarinense' region, Southern Brazil/Organizacao da comunidade e estrutura filogenetica do componente arboreo de um fragmento de floresta nebular no planalto catarinense

This study aimed to survey the community organization and the phylogenetic structure of tree species component in a nebular forest, in the municipality of Urubici, Santa Catarina state. A total of 25 plots (400 [m.sup.2]) were allocated, where all trees with circumference at breast height (cbh) equal or superior than 15.7 cm were measured (cbh) and identified. The Shannon index and phytosociological descriptors were determined. The dispersal syndromes of propagules were determined and the spatial distribution of each species was analyzed. The phylogenetic structure was evaluated by the values of 'Mean Pairwise Distance' (MPD) and Net Relatedness Index (NRI), determined through a phylogenetic tree built in function of the species sampled, an abundance matrix of species by plots and 1,000 simulations of a community with phylogenetic randomness organization. The spatial structure of the phylogenetic metrics was analyzed through I Moran Index. A total of 1,579 trees were sampled, belonging to 33 species, with Myrtaceae as the richest family. The low value of diversity (2.43), associated to low richness, is expected for nebular forest, where the environment is typically selective. The most representative species in the forest was Myrceugenia euosma (O.Berg) D.Legrand (VI = 24.51%). The predominant dispersal syndrome was zoochory (84.85%), followed by anemochory (15.15%); and the species showed predominantly a clustered spatial distribution. The community had variation in relation to the phylogenetic structure, with most plots showing no significant difference from the null model of complete randomness. Keywords: Araucaria Forest; Upper-montane Araucaria Forest; tree community; phylogeny. O presente estudo teve como objetivos conhecer a organizacao da comunidade e a estruturacao filogenetica do componente arboreo de um fragmento de Floresta Nebular em Urubici--SC. Para isso, foram alocadas 25 parcelas de 400 [m.sup.2], nas quais foi medida a circunferencia a altura do peito--CAP, e identificadas todas as arvores com CAP igual ou superior a 15,7 cm. Foram calculados o indice de diversidade de ShannonWiener e os descritores fitossociologicos. A sindrome de dispersao de propagulos e a distribuicao espacial de cada especie foram determinadas. A estruturacao filogenetica foi avaliada por meio dos valores de Mean pairwise distance (MPD) e de Net Relatedness Index (NRI), calculados a partir de uma arvore filogenetica construida em funcao das especies amostradas, de uma