Fabaceae and Cerrado savanna: Two descriptors of Brazilian extrafloral nectary plants

Extrafloral nectaries (EFNs) have been described in almost 4000 plant species, but there are several gaps in our knowledge of their occurrence and distribution. Here, we investigated the geographical distribution and richness of EFN-plants in Brazilian biomes (Cerrado, Atlantic Forest, Caatinga, Amazon, Pantanal, and Pampa). Data were extracted from 170 papers, and our analysis included only EFN-plants that interacted with ants. A total of 224 EFN-plant species in 115 genera and 48 families were registered in five biomes: Cerrado, Atlantic Forest, Caatinga, Pampa, and the Amazon. The Cerrado was evaluated in 64% of all publications, had the highest richness (90 species) and the most exclusive flora compared to the other biomes. In addition, the most studied species belonged to the Cerrado flora (e.g., Caryocar brasiliense). Fabaceae was the most speciose family, with 76 species, being dominant in all biomes and greatly surpassing other families. Only Fabaceae and Euphorbiaceae were found in all biomes, and in general, each biome had its own flora, as only 18 (of 224) plants were found in more than one biome. In a network analysis, Qualea grandilflora and Plathymenia reticulata were relatively more important than other species, as they connected biomes and increased the cohesion of the community. Our study shows that our understanding of EFN-plants is limited because the Fabaceae and Cerrado were overrepresented. A detailed record of species occurrence and distribution could be a valuable tool for studying the biodiversity of EFN-plants and their potential mutualistic interactions.