Synopsis of Loganiaceae in Pernambuco, Brazil

Abstract

Loganiaceae is a member of the Gentianales order and comprises about 460 species in 16 genera, being mainly distributed in the tropical regions of the world. The Brazilian Neotropical region is one of the centers of diversity for two of the richest genera of Loganiaceae, Spigelia and Strychnos, justifying floristic efforts to better understand family diversity in this region. This study aims to update the taxonomic knowledge about the Loganiaceae of the state of Pernambuco, Northeastern Brazil, providing an identification key, diagnostic characters of the species emphasizing vegetative features, illustrations and photos, distribution maps, and occurrence within Conservation Units. We analyzed collections from 18 local herbaria and conducted field expeditions to strategical locations of the state between 2017 to 2019. In total, we identified 16 species belonging to three genera: Mitreola (1), Spigelia (8) and Strychnos (7). As shown in previous studies, the morphology of the carpoatlas was determinant in the recognition of Spigelia species. In Pernambuco, Mitreola petiolata, Spigelia flemmingiana, S. laurina, S. scabra, Strychnos atlantica, S. divaricans, S. mattogrossensis, and S. trinervis were found only in the Atlantic Forest, while Spigelia alborubra, S. linarioides, S. pernambucensis, Strychnos gardneri, and S. rubiginosa were found only in the Caatinga domain. Spigelia anthelmia, S. polystachya, and Strychnos parvifolia have continuous distribution between both phytogeographic domains, presenting high morphological variability in these areas. Among the 16 loganiaceous species, 13 belong to 20 different Conservation Units spread over the two phytogeographic domains, highlighting the importance of maintaining these areas for the conservation of biodiversity in the state.