The importance of local environmental, hydrogeomorphological and spatial variables for beta diversity of macrophyte assemblages in a Neotropical floodplain

Abstract

Questions Understanding the processes that determine the variation in community composition (β‐diversity) is a major challenge in ecology, evolution, and conservation. Here we assess the importance of abiotic variables associated with local environmental features, hydrogeomorphology, and space to explain β‐diversity patterns in macrophytes by addressing the following questions: (1) Which are the sets of environmental, hydrogeomorphological, and spatial variables that contribute significantly to the spatial variation of macrophytes? (2) Which are their relative contributions to explaining the total β‐diversity, nestedness and turnover of macrophyte assemblages? Study Site Middle Paraná River floodplain, Argentina. Methods We sampled 20 lakes at low and high water levels in the Middle Paraná River floodplain. To investigate the relationship of total β‐diversity, turnover and nestedness with explanatory variables, we used the constrained analysis of principal coordinates (CAP). We used variation partitioning to assess the proportion of the variation related to each subset of variables (environmental, hydrogeomorphological and spatial). Results Among four alternatives considered to explain the spatial structure, the distance between lakes by watercourses best described the spatial organization of β‐diversity. Species turnover was largely explained by hydrogeomorphological variables, followed by spatial descriptors, whereas nestedness was exclusively related to spatial variables. Conclusions In the Middle Paraná River floodplain β‐diversity of macrophyte communities is partly shaped by turnover (mainly driven by the hydrogeomorphology of the floodplain) and nestedness (resulting from dispersal limitation by watercourses), but it also seems to be randomly organized (possibly because of random colonization and extinction, due to disturbances such as floods). Our work indicates that environmental pressures reflect differences between macrophyte communities of lakes with different geomorphological and hydrographical conditions. This suggests that certain ecological processes (such as species sorting) are driven at a higher degree by hydrogeomorphology than by local environment.

Ecology of Aquatic Macrophytes in Brazil: The Legacy of Francisco De Assis Esteves

“…Earlier studies usually investigated how communities change in response to habitat filtering at different spatial scales (Bini et al 1999, Rolon & Maltchick 2006, Rolon et al 2008. After the development of the metacommunity framework, other structuring processes were also tested, including competition (Boschilia et al 2008), connectivity, landscape features, human impacts (e.g., Rolon et al 2011, Rolon et al 2012, Ribeiro et al 2013, dispersal and neutral dynamics (Padial et al 2014, Schneider et al 2019, Trindade et al 2018. There is now a consensus that a set of interacting mechanisms explains macrophyte community structure.…”

“…Numerous studies have described and tried to explain the temporal variation of macrophyte communities (Thomaz et al 2009). In this context, the effects of flood pulses have been intensively studied given the importance of river-floodplain systems in Brazil (Sousa et al 2011, Catian et al 2018, Schneider et al 2019.…”

Nutrient Concentrations in Macrophytes from Lotic and Lentic Environments of the Middle Parana River, Argentina

“…Increased nutrients can also increase the growth of planktonic and benthic algae in wetlands, which, in turn, may compete with and inhibit macrophyte growth [32]. Macrophyte abundance and distribution in the Middle Parana River is determined by a complex process that involves hydrology, geomorphology, and changes in nutrient concentrations [33]. The different morphology and vegetation propagation of the two studied species influence the uptake and accumulation of nutrients in tissues [13].…”

Aquatic Macrophytes in Southern Amazonia, Brazil: Richness, Endemism, and Comparative Floristics

“…Aquatic macrophytes grow actively while permanently or periodically submerged, oating, or emerging from the water surface (Chambers et al 2008) and colonize most aquatic ecosystems to different degrees. The composition, richness, and cover of aquatic macrophytes may be determined by biotic factors such as climate, isolation, diversity of habitats, nutrients, and hydroperiod (Sousa et al 2011;Schneider et al 2019;Yang et al 2020). The richness of aquatic macrophytes depends mainly on the size of a wetland, although their composition may not follow this pattern (Maltchik et al 2007).…”