Aquatic herbaceous plants are especially suitable for mapping environmental variability in wetlands, as they respond quickly to environmental gradients and are good indicators of habitat preference. We describe the composition of herbaceous species in two oligotrophic wetland ecosystems, floodplains along black-water rivers (igapo) and wetlands upon hydromorphic sand soils (campinarana) in the Parque Nacional do Jau and the Reserva de Desenvolvimento Sustentavel Uatuma in Central Amazonia, both protected areas. We tested for the potential distribution range (PDR) of the most frequent species of these ecosystems, which are the ones that occurred in at least two of the sampled wetlands, using species distribution models (SDMs). In total, 98 aquatic herbaceous species were recorded, of which 63 occurred in igapos and 44 in campinaranas. Most igapo species had ample PDRs across the Neotropics, while most campinaranas species were restricted to the Amazon Basin. These results are congruent with studies that described similar distribution patterns for tree and bird species, which emphasizes a high degree of endemism in Amazonian campinarana. ... mehrHowever, we also found differences in the potential distribution of species between the two protected areas, indicating high environmental variability of oligotrophic ecosystems that deserve further investigation to develop effective measures for their conservation and protection.