Trait structure and functional diversity of periphytic algae in a floodplain conservation area

Abstract

We aimed to evaluate the structure of periphytic algae communities, the trait distribution and the patterns of functional diversity in the last non-dammed stretch of the Upper Parana River floodplain. We hypothesize that there is an increase in the functional diversity and a change o f the traits and environmental variables structure along this floodplain. We expected an increase in the functional diversity due to the increase in tributaries propagule input leading to a functional divergence, provided by deterministic processes. The sampling was in channels, lakes and rivers in a floodplain area covering 230 km of extension of the main river. The periphyton was obtained from scraping petioles of the floating macrophyte Eichhornia azurea (Sw.) Kunth. The traits evaluated were life form and strength and form of adherence to the substrate. The functional diversity was calculated from a functional dendrogram and assembly rules. The hypotheses proposed in this study were partially accepted, since there was no increase in functional diversity along the sampled area, but we observed a change in the structure of the functional traits along the different stretches of the floodplain. The results showed diatoms as the dominant algae, and functional convergence as the assembly rule prevalent for this community. There was a large difference between local environmental factors along the floodplain. The protected areas housed the greatest functional diversity values, which was apparently influenced by the increase in functional diversity, which can be explained by the limnological factors and the input of propagules from the tributaries to the Parana River. We noted the importance of the protected areas and local factors for assembly of this community.