Taxonomia de Bauhinia L. ser. Cansenia (Cercidoideae, Leguminosae) para o Nordeste do Brasil

Abstract

The diversity of ecosystems associated with the Brazilian Northeast territory has led to the establishment of numerous plant species. Among the existing taxa, those belonging to the genus Bauhinia L. are still little studied in this region and their taxonomic classification becomes difficult as it is based, in most cases, on few morphological characters. From this perspective, the objective was to carry out a taxonomic study of the genus Bauhinia with emphasis on the Section Pauletia Serie Cansenia, as well as to better characterize morphologically the species of this genus occurring in the Northeast of Brazil. On that occasion, field expeditions were carried out to collect botanical material and observe the species in their habitat. Furthermore, 10 herbaria were visited in the Northeast: CEPEC (BA), HUEFS (BA), UESC (BA), EAC (CE), HCDAL (CE), HST (PE), IPA (PE), PEUFR (PE), UFP (PE), TEPB (PI) and also consulted databases on online platforms such as REFLORA, specieslink, Jabot, Tropicos, Gbif, JSTOR, among others, totaling around 5000 specimens analyzed in 52 Brazilian and six foreign herbaria, including collections -type. Geographic distribution maps were prepared in SimpleMappr, using coordinates obtained from herbarium specimens. The conservation status of the species was assessed using IUCN criteria, with Extent of Occurrence (EOO) and Area of Occupancy (AOO) calculated using GeoCAT. 20 species and three varieties of Bauhinia ser. Cansenia were recorded occurring in the Northeast, where the State of Bahia and the Cerrado domain had the largest number of species. Bauhinia cheilantha and B. subclavata are widely distributed in the Northeastern States, while five species are restricted to the State of Bahia and four occur only in the State of Maranhão. Most species are endemic to Brazil, with six of them exclusive to the Northeast and five taxa considered threatened with extinction. Regarding taxonomic news, three species of Bauhinia ser. Cansenia were recently described for Northeast Brazil, namely: Bauhinia arleneae, B. andrade-limae and B. orbiculata. Bauhinia arleneae occurs in the central-eastern region of the State of Bahia in humid tropical forests and has entire, elliptical leaves with an acuminate apex and an obtuse base, glabrous leaf surfaces with three to five primary veins, paired flowers along the pseudoracemes and fruit with reticulate valves leathery-woody. Bauhinia andrade-limae is restricted to the States of Alagoas and Pernambuco, occurring in the Atlantic Forest and has bilobed, broadly ovate leaves with an obtuse apex and a chordate base, cartaceous and glabrous, generally with nine main veins, lenticelate stems, floral buds up to 5.3 cm long at anthesis and legume with woody, glabrous and reticulate valves. Bauhinia orbiculata is restricted to the northern part of Chapada Diamantina, in the central area of the State of Bahia and occurs in seasonally dry 'carrasco' shrub vegetation, being characterized by entire leaves with nine primary veins, rounded to obtuse apex and chordate base, abaxial side of the ferruginous leaf blade and linear, smooth floral buds. We provide here descriptions, synonyms, typifications, identification keys, illustrations, distribution maps and taxonomic comments for all species.