ABSTRACT We investigated the influence of Quaternary climate fluctuations on the current distribution of three species of Leguminosae (Fabaceae) occurring in the Chaco. Potential distribution models of Bauhinia hagenbeckii, Muellera nudiflora and Neltuma rubriflora with a supposed endemism area were generated. The Last Interglacial, Last Glacial Maximum, Holocene Middle and current scenarios were used. The species showed a potential distribution according to the South American biogeographic history regarding the glacier regression and the formation of the Dry Diagonal. The models for each Quaternary event exhibited a tolerable AUC ≥ 0.9 for the validations. The LGM was the event that favoured the current species establishment areas in the Dry Diagonal. Quaternary climatic events were related to the current Leguminosae distribution. Bauhinia hagenbeckii and Neltuma rubriflora present similar areas of environmental suitability. Muellera nudiflora models with areas of environmental suitability were larger for the LIG and Holocene than for areas from other periods. All scenario models (LGM, HM and current scenario) highlighted the potential distribution of the three species concomitant with the glacier regression events and were consistent with the history of formation of South American dry areas.

Resumo O Chaco é maior domínio de florestas contínuas da América do Sul e agrega distintas famílias botânicas com destaque à Leguminosae. A elevada riqueza e diversidade de membros de Leguminosae, sobretudo de Papilionoideae, aliada à distribuição de determinados gêneros comuns às florestas secas tem motivado a investigação deste interessante grupo de plantas nas formações chaquenhas do Brasil. Este estudo florístico-taxonômico fornece chave de identificação, descrições morfológicas, ilustrações, comentários taxonômicos e ambientes preferenciais das espécies de Papilionoideae ocorrentes no Chaco do Brasil. Confirmamos a ocorrência de 45 espécies, distribuídas em 21 gêneros. Os gêneros com maior número de espécies são Aeschynomene (10), Galactia (4), Indigofera (4), Stylosanthes (4) e Desmodium (3). Os demais encontram-se representados por duas ou uma espécie: Arachis (2), Centrosema (2), Macroptilium (2), Rhynchosia (2), Amburana (1), Ancistrotropis (1), Camptosema (1), Crotalaria (1), Discolobium (1), Dolichopsis (1), Geoffroea (1), Machaerium (1) e Muellera (1), Sesbania (1), Tephrosia (1) e Zornia (1). Espécies dos gêneros Muellera, Dolichopsis e Geoffroea são exclusivas de áreas secas da América do Sul. Aeschynomene magna é registrada pela primeira vez para o Brasil, e considerada endêmica do Chaco. Stylosanthes maracajuensis é o primeiro registro para o Chaco.

Abstract 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.