Floristic composition and similarity of a conservation area in the semiarid region of Paraíba State, Northeastern Brazil

Abstract We present here a floristic survey of the angiosperms found in the Reserva Ecológica Olho d’Água das Onças (REODO) in the semiarid region of Paraíba State, Brazil, to provide a basis for proactive conservation projects there. Fifteen excursions were carried out between August/2022 and April/2024 employing traditional methods of collecting and herborization of botanical material. The collections obtained were incorporated into the Manuel de Arruda Câmara Herbarium (HACAM) at the State University of Paraíba (UEPB), Campus I. We examined the floristic relationships between the study area and 15 other floristic surveys throughout the semiarid region of Paraíba State using a similarity analysis based on the Jaccard index. Two hundred and fifty species distributed among 168 genera and 50 families of angiosperms were identified with the following growth forms: herbaceous (74 spp.), subshrub (60 spp.), shrub (48 spp.), climber (45 spp.), arboreal (17 spp.), epiphytic (3 spp.), and parasitic (3 spp.). The most representative families were Fabaceae (38 spp.), Euphorbiaceae (24 spp.), Convolvulaceae (19 spp.), Malvaceae (18 spp.), Asteraceae (11 spp.), and Poaceae (11 spp.). The most representative genera were Ipomoea L. (8 spp.), Croton L. (7 spp.), Sida L. (7 spp.), Chamaecrista (L.) Moench (6 spp.), and Mimosa L. (5 spp.). Heteropterys arcuata C. Pessoa & Amorim (Malpighiaceae) and Solanum fernandesii V.S. Samp. & R. Moura (Solanaceae) were recorded for the first time in Paraíba State; Urvillea stipitata Radlk (Sapindaceae) represents a new record for the Caatinga. Similarity analysis revealed that the flora of REODO is more closely related to that of protected areas throughout the semiarid region of Paraíba State, underscoring its conservation priority. The study area was therefore found to contain significant floristic richness, especially within the context of the Caatinga, with 30 species endemics to this domain. Resumo O presente estudo compreende o levantamento florístico das angiospermas da Reserva Ecológica Olho d’Água das Onças (REODO), Picuí, semiárido da Paraíba, Brasil, objetivando fornecer a base para projetos conservacionistas na área. Foram realizadas 15 incursões durante o período de agosto de 2022 e abril de 2024, seguindo os métodos usuais de coleta e herborização de material botânico. A coleção obtida foi incorporada ao Herbário Manuel de Arruda Câmara (HACAM), pertencente à Universidade Estadual da Paraíba (UEPB), Campus I. Verificaram