TURNOVER AND NESTEDNESS IN MACROPHYTE ASSEMBLAGES: THE IMPORTANCE OF LOCAL ENVIRONMENTAL, HYDROGEOMOPHOLOGICAL AND SPATIAL VARIABLES

CUNHA, E.R.; SCHNEIDER, B.; THOMAZ, S.M.; MARCHESE, M.

Neiva

Congreso; I Congreso Internacional y II Congreso Nacional de Ríos y Humedales.; 2017

Centro de Investigación en Ciencias y Recursos GeoAgroAmbientales CENIGAA

Beta diversity in macrophyte communities has been studied through the niche perspective assuming that the species distribution is strongly controlled by local environmental variables. Here, we investigated the relationship between environmental variables (local environmental factors (LEV), hydrogeomorphological (HGV) and spatial (SPV)) and patterns of beta diversity in macrophyte assemblages. We sampled 21 connected and disconnected lakes twice during the dry seasons and twice during the flood seasons in the Middle Paraná River floodplain. We quantified beta diversity using indexes of Podani family derived from Jaccard coefficient. To investigate the relationship between the variation of total β-diversity, turnover and nestedness and the explanatory variables we used constrained analysis of principal coordinates (CAP). Variables were separately selected using forward stepwise procedure (α = 0.05) within each of the sets of environmental variables (LEV, HGV and SPV). Performances of alternative spatial structures were compared using R2 values and only the best spatial structure was used in further analysis. We used variation partitioning to assess the proportion of the variation related to each subset of variables. The contribution of environmental factors to explain variance in turnover was greater than the contribution to explain nestedness. Species turnover was mainly related to HGV (R2: 0.117; F: 2.136; p: 0.001), represented by connectivity, distance to the river, lake altitude and water level. Spatial structure was also an important aspect explaining the variance in species turnover (R2: 0.047; F: 1.705; p: 0.001). Contrastingly, species nestedness was exclusively related to space and such relationship were quite smaller than the one observed for species turnover (R2: 0.039; F: 1.282; p: 0.03). Contrary to our expectations, LEV did not explain either of the two components of beta diversity. Contribution of spatial structure in variation of both turnover and nestedness suggests that neutral process may partially determine beta diversity structure of macrophyte assemblages in floodplain. In addition, HGV are most likely to drive process of species sorting once it was significantly related to species turnover across environments.