Hidden Diversity in the Iberá Wetlands: Fern and Lycophyte Richness and Biogeographic Boundaries

The Iberá Wetlands in northeastern Argentina constitute the second largest wetland system in South America, yet the fern and lycophyte flora of this region remains poorly documented. The aims of this work were to update the species richness of these plant groups, evaluate the intensity of collecting efforts, identify conservation priorities, estimate the potential true species richness, and make biogeographical inferences. We compiled a database of species from multiple sources, and the study area (21,853 km2) was divided into 19 grid cells for analysis. Sampling effort and species richness were quantified, and non-parametric estimators (Chao2, ICE, Jack2) were used to evaluate inventory completeness. Several similarity analyses were performed using the Jaccard index, incorporating reference areas from the Chaco and Paranaense phytogeographic provinces. The Ituzaingó–La Paz geological fracture and the geological formations present in the area were also considered. We recorded 76 taxa, whereas estimators suggested a potential richness of 130–140 species. The center of the Iberá Wetlands showed the lowest sampling effort, while the eastern sector exhibited the highest species richness. The distribution of species appears to be correlated with geological formations. These findings emphasize the importance of continuing sampling in the area.