Floristic composition, structure and species-area relationships on a neotropical inselberg in southeastern Brazil.

The inselberg vegetation, in general, occurs in patches that vary in size, shape, number of plant species and are surrounded by a bare rock. The present study evaluated the species composition, structural analysis, and species-area relationships of vegetation patches on a neotropical inselberg in Rio de Janeiro state, southeastern Brazil. A total of 69 vascular plant species, from 31 families, were sampled in 84 vegetation patches varying in area from 0.02 to 500 m2, totaling 0.33 ha. Fabaceae and Cactaceae were the most representative families. Vellozia plicata and Selaginella sellowii presented the highest relative frequencies, relative dominances and importance values and were the most successful in the colonization of the studied rocky outcrop. A linear regression showed a positive correlation between patch size and species richness. Phanerophytes were the predominant life-form, with small patches being less rich in species and dominated by Selaginella mats. Our results suggest that the vegetation patches on the "Morro do Itaoca" inselberg currently represent a refuge against fire and other anthropogenic disturbances for many typical species of the surrounding matrix. In addition, the locality is home to endemic and endangered species, which reinforces its importance for conservation actions. [ABSTRACT FROM AUTHOR]