The Chaco is the largest area of continuous forests in South America and assembles different botanical families with emphasis on Leguminosae. The high richness and diversity of Leguminosae members, especially from Papilionoideae, associated with the distribution of certain genera common to dry forests, have motivated the investigation of this interesting group of plants in Brazilian Chaco formation. This floristic-taxonomic study provides an identification key, morphological descriptions, illustrations, taxonomic comments and preferred environments of Papilionoideae species occurring in the Brazilian Chaco. We confirmed the occurrence of 45 species belonging to 21 genera. The genera with the largest number of species are Aeschynomene (10), Galactia (4), Indigofera (4), Stylosanthes (4) and Desmodium (3). The others are represented by two or one species Arachis (2), Centrosema (2), Macroptilium (2), Rhynchosia (2), Amburana (1), Ancistrotropis (1), Camptosema (1), Crotalaria (1), Discolobium (1) Dolichopsis (1), Geoffroea (1), Machaerium (1) and Muellera (1), Sesbania (1), Tephrosia (1) and Zornia (1). Species of genera Muellera, Dolichopsis and Geoffroea are unique to dry areas of South America. Aeschynomene magna is registered for the first time in Brazil and considered endemic to the Chaco. Stylosanthes maracajuensis is recorded for the first time for Chaco areas.
Fabaceae; thorny forests; seasonally dry tropical forests; floristic; richness; taxonomy