Macrophyte species richness and composition are correlated with canopy openness and water depth in tropical floodplain lakes

Abstract

Aquatic macrophytes colonize a variety of environments, and they play important roles in ecosystem function and in community structure. One key challenge for aquatic ecologists is to investigate the environmental factors that drive the richness and distribution of these plants. In this study, we assessed the importance of selected morphometric variables and of the canopy openness of the riparian vegetation to explain macrophyte species richness and composition. We sampled macrophytes along gradients of depth, littoral slope, distance from the connection with the river, and canopy openness in floodplain lakes connected with the Upper Paraná River. We used quadrats to survey a total of 40 sites in 11 lakes. We recorded 31 macrophyte species and found that macrophyte richness was best and positively correlated with canopy openness. This correlation suggests that canopy openness plays an important role as an environmental filter, regulating the amount of light availability for macrophytes. Macrophyte species composition was best correlated with depth, indicating that zonation of macrophyte species also occurs in these shallow lakes. These findings emphasize the importance of morphometric variables and canopy openness for structuring macrophyte assemblages. In addition, our results suggest that canopy openness and depth may be considered in management strategies aiming to recover macrophyte diversity and the processes mediated by aquatic macrophytes in small and shallow floodplain lakes.

Environmental drivers of freshwater macrophyte diversity and community composition in calcareous warm‐water rivers of America and Africa

“…Our results support previous studies which suggest that, in freshwater systems, local driving factors (chemical, physical or biological) seem to be of overriding importance in determining whether or not macrophyte diversity at an individual site is depressed below the optimal level within a given geographical region (e.g. Baattrup-Pedersen, Szoszkiewicz, Nijboer, O'Hare, & Ferreira, 2006;Bando et al, 2015;Chappuis et al, 2012;Kennedy et al, 2015;Lang & Murphy, 2012;Morandeira & Kandus, 2015;Rolon & Matchik, 2006;Schneider et al, 2015;Tapia Grimaldo et al, 2016). Physical size of individual rivers, however, seemed to be of little importance in influencing a-diversity.…”

“…In contrast, there has been quite a substantial macrophyte survey effort in the Neotropics, particularly in South American freshwater systems (e.g. Amaral, Bittrich, Faria, Anderson, & Aona, 2008;Bando, Michelan, Cunha, Figueiredo, & Thomaz, 2015;Bertoli, 1996;Bottino, Calijuri, & Murphy, 2014;Murphy et al, 2003;Neiff, Casco, Mari, Di Rienzo, & Poi, 2014;Rolon & Matchik, 2006;Schneider, Cunhab, Marchese, & Thomaz, 2015;Sousa, Thomaz, & Murphy, 2010Thomaz, Carvalho, Padial, & Kobayashi, 2009;Varandas Martins et al, 2013), although less so in Central America (e.g. Anonymous, 1999;Bonilla-Barbosa, 2004;Crow, 1993;Philbrick & Alejandro, 1995).…”

Egg‐laying traits reflect shifts in dragonfly assemblages in response to different amount of tropical forest cover

“…Endophytic and epiphytic species that lay eggs in macrophytes did not respond to a decline of the forest cover. In streams with low amounts of forest cover, we expected a larger amount of macrophytes due to higher availability of light, which favours the growth of some plant species (Wood et al, 2012;Bando et al, 2015). The presence and amount of aquatic plants have a great influence on the richness of dragonfly species that lay eggs in them (see Vilela et al, 2016), and may have a direct impact on larval mortality and emergence rates by providing shelter and perches (Tavares et al, 2017).…”

“…Although there is no general consensus, species that exhibit exophytic oviposition use light polarisation on the stream water surface as a cue for oviposition site selection (Corbet, 1999;Stevani et al, 2000;Van de Koken et al, 2007;Paulson, 2009;De Marco et al, 2015). The absence of riparian forest can increase sediment deposition along stream channels, which may modify parts of the lotic channels, form pools and/or reduce stream flow, favouring species that lay eggs directly on the water surface, (ii) there would be an increase in the richness of endophytic and epiphytic species that oviposit in macrophytes in relation to forest cover loss, as aquatic plants are favoured in open environments and intermediate stages of forest cover, facilitating the development and reproduction in these two groups (Loo et al, 2009;Paulson, 2009;Guillermo-Ferreira & Del-Claro, 2011;Wood et al, 2012;Bando et al, 2015;Tavares et al, 2017), and (iii) a decrease in the richness of the remaining epiphytic species (excluding those that oviposit in macrophytes), in relation to forest cover loss, because the absence of riparian forest along streams leads to a decrease and loss of available oviposition sites, such as rocks (due to sedimentation), roots, stems and leaves, decreasing the places for adult perchers to be able to thermoregulate, forage, defend territories, attract mates, copulate, roost at night, and have protection from adverse weather and predators. The riparian zone also helps in the maintenance of the physical structure of the river channels, avoiding the modification caused by excessive sediment deposition, essential for maintaining epiphytic species larval habitats (May, 1979(May, , 1991Corbet, 1999;Paulson, 2009;Remsburg & Turner, 2009;De Marco et al, 2015).…”

Niche-breadth of freshwater macrophytes occurring in tropical southern African rivers predicts species global latitudinal range

“…The basic underlying issue of macrophyte diversity support functioning (and threats to it) in tropical river systems (e.g. Bando et al, 2015;Santos and Thomaz, 2007) is however clearly in urgent need of further research.…”