Abiotic factors drive the structure of aquatic plant assemblages in riverine habitats of the Brazilian “Pantanal”

The “Pantanal” wetland is one of the largest centers of diversity of aquatic macrophytes of Brazil. The objective of this work was to present a checklist of aquatic macrophytes, and to investigate structure and patterns of occurrence regarding physico-chemical parameters, at Amolar, in the Paraguay River sub-region, in the mid-western “Pantanal” wetland, Corumbá (MS). No previous aquatic plant study has been carried out there so far. The study was conducted in June 2009 in 391 plots (0.5 × 0.5 m). We recorded 65 species of aquatic macrophytes, from 49 genera and 27 families. The richest families were Fabaceae, Poaceae, Convolvulaceae, Onagraceae, and Lentibulariaceae. The most representative life forms were emergent and free floating, comprising the most frequent species: Hymenachne amplexicaulis (Rudge) Nees, Salvinia auriculata Aubl., Ricciocarpos natans (L.) Corda, Lemna aequinoctialis Welw. and Azolla filiculoides Lam. presented the highest relative cover, as well as the highest importance value, followed by S. auriculata. The structure of the community of aquatic macrophytes presents relation with physico-chemical variables, chiefly depth: many species occurred exclusively in shallow areas and others in deep zones. The life forms partially explain the species zonation of macrophytes in relation to depth.