Diversity and conservation of legumes in the Gran Chaco and biogeograpical inferences

Abstract

The Gran Chaco is a wide ecologic-geographic region comprising northern Argentina, western Paraguay, southern Bolivia and the southwestern extreme of Brazil. This region exhibits extreme temperatures, annually regular frosts, and sedimentary soils; it has been dramatically threatened by agriculture expansion in recent decades. Therefore, increasing knowledge of plant diversity is critical for conservation purposes. We present a Legume checklist of the Gran Chaco ecoregion including conservation status of its endemic species. Leguminosae is the third most diverse plant family in the Neotropics. Assuming a rigorous spatial definition of the Gran Chaco, we recorded 98 genera, 362 species, and 404 specific and infraspecific taxa. Endemic/typical taxa were 17%, comparable to adjacent tropical plant formations, and they were found in higher percentages in Caesalpinioideae (24%) and Cercidoideae (33%) than Papilionoideae (11%) subfamily. We also analyzed the plant diversity comparing lineages and subregions. The Gran Chaco Legumes are predominantly widespread generalists, or they belong to either Chaco sensu stricto or Neotropical Seasonally Dry Tropical Forest (SDTF) lineages. Though the Humid Chaco registered the highest species richness, Dry Chaco and Sierra Chaco, the most threatrened subregions, exhibited the highest percentages of exclusive and proper Chaco-lineage species. These results suggest that diversification of Legumes has been most relevant in Dry Chaco and Sierra Chaco, probably by their more demanding and harsh environmental conditions limiting the dispersion of generalists or intrusive-invading species. This study is paramount to reach an improved delimitation of the Gran Chaco ecoregion in transitional areas with the SDTF and Cerrado formations. Conservation status is critical in genera of high economic interest, such as Arachis , Mimosa and Prosopis . At least one third of endemic taxa exhibit a critical status of conservation or are endangered, many of them being relevant to inbreeding program or exhibiting multiple economic uses.

Species representativeness of Fabaceae in restrictive soils explains the difference in structure of two types of Chaco vegetation

“…rubriflora, P. praecox and M. hexandra -Baptista et al 2016). Prosopis and Mimosa are among the most diverse genera of the Chaco (Morales et al 2019), with P. rubriflora being considered an indicative species of the Domain (Pott & Pott 1994;Oliveira-Filho et al 2006). These species are nodulatory (Burkart 1976) and are often found in clusters interspersed with other species (Lima 2012), which suggests that it can act as a nursing plant.…”

Biogeography of different life forms of the southernmost neotropical tank bromeliad

“…Records are based on data from herbaria, bibliography, digital datasets and personal observations (N = 1001 records). Biogeographic map based on Särkinen et al, (2011) and Morales et al, (2019) were recorded on sites with higher AET/PET, PET, MAP, P dry , and percentage of clay, and lower pH, BSAT, and CEC, than saxicolous and terrestrial plants (Figure 4).…”

Leguminosae endemic to the Chaco facing quaternary climate fluctuations

“…On a global scale, Leguminosae serve as a model for studies based on phytogeographic approaches since they are a highly successful group occupying most of the terrestrial habitats such as dry, humid and temperate rainforests, savannas, fields, and deserts, thereby representing the protagonists of the global (Schrire et al 2005) and regional biota, mainly in the Neotropics (Simon & Proença 2000;Flores & Miotto 2005;Flores & Tozzi 2008;Cardoso & Queiroz 2011;Werneck 2011;Morales et al 2019). The Chaco, the largest continuous area of dry forests in South America, has a high richness and endemism when compared to other dry areas (Dryflor 2016).…”