Attacking shortfalls of aquatic plant diversity in the São Francisco Basin, Brazil's fourth hydrological region

Access to taxonomic and biogeographical information about aquatic plants at large spatial scales, such as river basins, poses challenges due to the temporal and spatial dynamics of ecosystems and human limitations in research. Here, we investigated the diversity, endemism, and distribution of aquatic plants in the São Francisco River Basin, which spans over 600,000 km² of Brazilian territory. We compiled data from digital repositories and collected data through floristic inventory associated with the Integration Project of the São Francisco River (PISF). We discovered 853 aquatic plant species in the basin, with 788 native and 138 endemic to Brazil. The highest record density, species numbers, and endemism index were recorded in areas with large hydraulic developments, such as hydroelectric power plants and PISF canals in the middle lower and lower São Francisco regions, as well as the upper region near an urban center. Field expeditions from the PISF contributed 16% of the total records and 32.9% of the total richness, documenting 16 exclusive species. Our results highlight the diversity and distribution of aquatic plants within a hydrographic basin covering over 8% of Brazil, emphasizing the importance of primary data obtained through environmental licensing linked to infrastructure works in addressing biodiversity shortfalls.

Keywords:
Caatinga Phytogeographic Domain; Environmental Licensing; Macrophyte; River Transposition; São Francisco River