Flora and similarities of a rocky outcrop in the Caatinga, eastern region of South America

Rocky environments show great habitat heterogeneity and very specific microclimatic characteristics that select for appropriately adapted floristic assemblages. A floristic survey was carried out on a rock outcrop in the driest portion of the Cariri Environmental Protection Area (APA) in Paraíba State, northeastern Brazil, to determine its similarity to other Caatinga sites. We recorded 128 species distributed among 103 genera and 52 families. Fabaceae, Convolvulaceae, Malvaceae, Euphorbiaceae, Asteraceae, Cactaceae, Bromeliaceae, Rubiaceae, and Poaceae were the most representative families in terms of numbers of species, with a high representation of herbaceous and shrub components and a predominance of typically Neotropical species, in addition to endemic taxa. Pectis linifolia L. (Asteraceae) is recorded here for the first time in the Paraíba state, Brazil. Similarity analysis evidenced that the study area, located in an extremely dry Caatinga zone, evidenced floristic relationships with other rocky outcrops in more humid areas, suggesting that habitat type is important for selecting specific groups, following the theory of refuges.