Fabaceae no Chaco: riqueza, distribuição e dispersão

Abstract

Chaco, an exclusively South American domain, occurs in central-northern Argentina, southeastern Bolivia, western Paraguay, and the western edge of Brazil. This domain aggregates two sectors, dry and wet, according to the precipitation gradient. Fabaceae, considered cosmopolitan, has significant richness in Chaco formations, possibly resulting from different morphological, anatomical and physiological strategies of its representatives. Additionally, studies have evidenced the predominance of diaspore dispersion by abiotic factors in places with low rainfall and the predominance of zoochory in regions with high rainfall. This study, for Chaco's tree and shrub legumes, is organized into two chapters. The first objective was to verify the richness of tree and shrub legumes in Chaco sectors under different precipitation regimes, to show patterns of tax distribution, to compare Chaco taxonomic distinction values with those of other domains and to evaluate which Chaco sector has greater filtering of species. The second aimed to define the types of primary and secondary dispersion syndromes and to evaluate whether there is a relationship between dispersion syndromes, fruit types and growth habits with the precipitation gradient. Occurrence data for Fabaceae species in Chaco were obtained from the Global Biodiversity Information (GBIF) site and climate data were taken from the online repository www.worldclim.org. The Chaco tree and shrub legumes totaled 295 species distributed in 80 genera, with different geographic distribution patterns. The taxonomic distinction indicates filtering in drier regions of the Chaco. Abiotic syndromes prevail among Chaco legumes in relation to the precipitation gradient, and precipitation is indeed a model for the distribution of legume species.