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Aim: We propose a novel approach that considers taxonomic uniqueness, functional uniqueness and environmental uniqueness and show how it can be used in guiding conservation planning. We illustrate the approach using data for lake biota and environment. Location: Lake Puruvesi, Finland. Methods: We sampled macrophytes and macroinvertebrates from the same 18 littoral sites. By adapting the original "ecological uniqueness" approach, we used distance‐based methods to calculate measures of taxonomic (LCBD–t), functional (LCBD–f) and environmental (LCEH) uniqueness for each site. We also considered the numbers and locations of the sites needed to protect up to 70% of total variation in taxonomic, functional or environmental features in the studied part of the lake. Results: Relationships between taxonomic (LCBD–t), functional (LCBD–f) and environmental (LCEH) uniqueness were generally weak, and only the relationship between macrophyte LCBD–t and LCBD–f was statistically significant. Overall, however, if the whole biotic dataset was considered, macroinvertebrate LCBD–f values showed a consistent positive relationship with macrophyte LCBD–f. Depending on the measure of site uniqueness, between one‐third to one half of the sites could help protect up to 70% of the ecological uniqueness of the studied part of Lake Puruvesi. Main conclusions: Although the dataset examined originated from a large lake system, the approach we proposed here can be applied in different ecosystems and at various spatial scales. An important consideration is that a set of sites has been sampled using the same methods, resulting in species and environmental matrices that can be analysed using the methodological approach proposed here. This framework can be easily applied to grid‐based data, sets of islands or sets of forest fragments. We suggest that the approach based on taxonomic, functional and environmental uniqueness will be a useful tool in guiding nature conservation and ecosystem management, especially if associated with meta‐system ideas or network thinking. [ABSTRACT FROM AUTHOR]

Arctic and sub‐Arctic lakes in northern Europe are increasingly threatened by climate change, which can affect their biodiversity directly by shifting thermal and hydrological regimes, and indirectly by altering landscape processes and catchment vegetation. Most previous studies of northern lake biodiversity responses to environmental changes have focused on only a single organismal group. Investigations at whole‐lake scales that integrate different habitats and trophic levels are currently rare, but highly necessary for future lake monitoring and management.We analysed spatial biodiversity patterns of 74 sub‐Arctic lakes in Norway, Sweden, Finland, and the Faroe Islands with monitoring data for at least three biological focal ecosystem components (FECs)—benthic diatoms, macrophytes, phytoplankton, littoral benthic macroinvertebrates, zooplankton, and fish—that covered both pelagic and benthic habitats and multiple trophic levels.We calculated the richnessrelative (i.e. taxon richness of a FEC in the lake divided by the total richness of that FEC in all 74 lakes) and the biodiversity metrics (i.e. taxon richness, inverse Simpson index (diversity), and taxon evenness) of individual FECs using presence–absence and abundance data, respectively. We then investigated whether the FEC richnessrelative and biodiversity metrics were correlated with lake abiotic and geospatial variables. We hypothesised that (1) individual FECs would be more diverse in a warmer and wetter climate (e.g. at lower latitudes and/or elevations), and in hydrobasins with greater forest cover that could enhance the supply of terrestrial organic matter and nutrients that stimulated lake productivity; and (2) patterns in FEC responses would be coupled among trophic levels.Results from redundancy analyses showed that the richnessrelative of phytoplankton, macrophytes, and fish decreased, but those of the intermediate trophic levels (i.e. macroinvertebrates and zooplankton) increased with decreasing latitude and/or elevation. Fish richnessrelative and diversity increased with increasing temporal variation in climate (temperature and/or precipitation), ambient nutrient concentrations (e.g. total nitrogen) in lakes, and woody vegetation (e.g. taiga forest) cover in hydrobasins, whereas taxon richness of macroinvertebrates and zooplankton decreased with increasing temporal variation in climate.The similar patterns detected for richnessrelative of fish, macrophytes, and phytoplankton could be caused by similar responses to the environmental descriptors, and/or the beneficial effects of macrophytes as habitat structure. By creating habitat, macrophytes may increase fish diversity and production, which in turn may promote higher densities and probably more diverse assemblages of phytoplankton through trophic cascades. Lakes with greater fish richnessrelative tended to have greater average richnessrelative among FECs, suggesting that fish are a potential indicator for overall lake biodiversity.Overall, the biodiversity patterns observed along the environmental gradients were trophic‐level specific, indicating that an integrated food‐web perspective may lead to a more holistic understanding of ecosystem biodiversity in future monitoring and management of high‐latitude lakes. In future, monitoring should also focus on collecting more abundance data for fish and lower trophic levels in both benthic and pelagic habitats. This may require more concentrated sampling effort on fewer lakes at smaller spatial scales, while continuing to sample lakes distributed along environmental gradients. [ABSTRACT FROM AUTHOR]

A multi-faceted approach is needed to better understand how the beta diversity of aquatic assemblages responds to ecological gradients. Using distance-based RDA and variance partitioning, we explored the different components of total beta diversity (replacement and richness difference) based on taxonomic, functional, and phylogenetic data of aquatic macrophytes along environmental and spatial gradients across 49 tropical floodplain lakes in the Pantanal of Mato Grosso in the dry season. We found that taxonomic beta diversity was driven by species replacement, while functional beta diversity was mostly contributed by richness difference and phylogenetic beta diversity was equally contributed by both components. Taxonomic and functional beta diversities were driven by environmental variables, connectivity variables, and directional spatial processes. Phylogenetic beta diversity was mainly affected by the connectivity between the sites and their distance from the river. The relationship between environmental variables and beta diversity indicates that a selection of species with similar functional and phylogenetic characteristics co-occurs at a site. The low connectivity between sites and the increased distance between the lakes and the river suggested dispersal limitation, which was due to the absence of directional exchange of species between lakes. Our findings provided new insights into the beta diversity patterns of aquatic macrophytes and their underlying causes in tropical floodplains. [ABSTRACT FROM AUTHOR]

Documenting the patterns of biological diversity on Earth has always been a central challenge in macroecology and biogeography. However, we are only beginning to generate an understanding of the global patterns and determinants of macrophyte diversity. Here, we studied large‐scale variation and community‐environment relationships of lake macrophytes along climatic and geographical gradients using regional data from six continents. We applied statistical routines typically used in the context of metacommunity studies to provide novel insights into macrophyte community compositional patterns within regions worldwide. We found that lake macrophyte metacommunities followed clumped species replacement structures, suggesting that two or more species groups were responding similarly to the environment within regions. Underlying such general convergence, our results also provided evidence that community‐environment relationships were largely context‐dependent, stressing that no single mechanism is enough to account for the complex nature of compositional variation. Surprisingly, we found no general relationships between functional or phylogenetic composition and main metacommunity types, suggesting that linking multi‐trait and evolutionary information to the elements of metacommunity structure is not straightforward. Our findings highlight that global conservation initiatives and biodiversity protection need to capture environmental variation at the metacommunity level, and acknowledge the highly context‐dependent patterns in the community‐environment relationships of lake macrophytes. Overall, we emphasize the need to embrace the potential complexity of ecological inferences in metacommunity organization across the globe. [ABSTRACT FROM AUTHOR]

Functional homogenisation occurs across many areas and organism groups, thereby seriously affecting biodiversity loss and ecosystem functioning. In this study, we examined how functional features of aquatic macrophytes have changed during a 70-year period at community and species levels in a boreal lake district. At the community level, we examined if aquatic macrophyte communities showed different spatial patterns in functional composition and functional richness in relation to main environmental drivers between the time periods. We also observed each species in functional space to assess if species with certain sets of traits have become more common or rare in the 70-year study period. We found changes in the relationship between functional community composition and the environment. The aquatic macrophyte communities showed different patterns in functional composition between the two time periods, and the main environmental drivers for these changes were partly different. Temporal changes in functional richness were only partially linked to concomitant changes in the environment, while stable factors were more important. Species' functional traits were not associated with commonness or rarity patterns. Our findings revealed that functional homogenisation has not occurred across these boreal lakes, ranging from small oligotrophic forest lakes to larger lakes affected by human impacts. [ABSTRACT FROM AUTHOR]

Deconstructing beta diversity patterns into site or species contributions is a modern approach to understand the factors affecting variation in biodiversity. In this context, estimating the Local Contribution to Beta Diversity (LCBD) and the individual Species Contribution to Beta diversity (SCBD) have been shown to be a good approach to improve knowledge of the drivers of beta diversity. We examined the beta diversity of macrophytes surveyed at 49 floodplain lakes in the Pantanal Wetlands in Brazil during the dry season. We found that, unexpectedly, total species richness was not correlated to LCBD values, but the number of rare species per site was possibly related to LCBD values. Three variables from Moran's Eigenvector Maps (MEM), water transparency and organic matter were the main variables related to LCBD values. The species with highest contributions to beta diversity were those that occurred at approximately half of the surveyed sites. The same patterns were observed when analysing macrophyte data divided by life forms. Of the life forms, floating macrophytes contributed most to beta diversity. The understanding of which factors drive variation in LCBD and which kind of species most contribute to SCBD are fundamental to performing efficient conservation and restoration programs to maintain the structural, functional and ecological diversity of the macrophyte communities in dynamic floodplain ecosystems. [ABSTRACT FROM AUTHOR]

It has been predicted that spatial beta diversity shows a decreasing trend in the Anthropocene due to increasing human impact, causing biotic homogenisation. We aimed to discover if vascular aquatic macrophyte communities show different spatial patterns in beta diversity in relation to land use and environmental characteristics in different decades from 1940s to 2010s. We aimed to discover if spatial structures differ between species‐, phylogeny‐ and functional‐based beta diversity. We used presence–absence data of aquatic macrophytes from five decades from small boreal lakes. We utilized generalised dissimilarity modelling to analyse spatial patterns in beta diversity in relation to environmental gradients. We found that lake elevation and pH were the most important variables in each decade, while land use was not particularly important in shaping beta diversity patterns. We did not find signs of a decreasing trend in spatial beta diversity in our study area during the past 70 yr. We did not find signs of either biotic homogenisation or biotic differentiation (taxonomic, phylogenetic or functional). Vascular aquatic macrophyte communities showed only slightly different beta diversity patterns in relation to human impact across decades. The patterns of different facets of beta diversity diverged only slightly from each other. Lake position in the landscape, reflecting both natural connectivity and lake characteristics, explained the patterns found in beta diversity, probably because our study area has faced only modest changes in land use from 1940s to 2010s when compared globally. Our study highlights the fact that biotic homogenisation is not an unambiguous process acting similarly at all spatial and temporal scales or in different environments and different organism groups. [ABSTRACT FROM AUTHOR]

Aim: Conserving freshwater biodiversity in a rapidly changing world requires updated planning schemes and research efforts. Geodiversity – the diversity of Earth surface forms, materials and processes – and biodiversity are interlinked at a fundamental level. This relationship is being considered in a growing number of studies, yet research from freshwater environments is scarce. We used geodiversity (rock‐type, soil‐type and geomorphological richness), local and climatic variables to explore whether geodiversity can be used as a surrogate for aquatic plant species richness in lakes and rivers. Location: Finland. Taxon: Aquatic plants. Methods: We compared geodiversity variables (measured within 1‐km2 grid cells) to well‐studied local (e.g. area, alkalinity) and climate (e.g. growing degree‐days) variables, and examined the patterns between habitat types (lakes and rivers) and among all taxa and major functional groups (helophytes and hydrophytes). We modelled lake (n = 145) and river (n = 146) plant species richness with generalized linear models, and further partitioned variation to measure the independent and shared contributions of the geodiversity, climate and local environmental variable groups. As a complementary analysis, and to identify single important variables explaining variation in aquatic plant species richness, we utilized boosted regression trees. Results: We found a positive relationship between aquatic plant species richness and catchment geodiversity variation with recurring patterns across two different freshwater habitat types and two aquatic plant functional groups. Higher variation in geodiversity (measured at landscape scale) supported higher freshwater biodiversity (measured at the local scale) of lakes and rivers. Main conclusions: Geodiversity can be a useful addition to biodiversity modelling, and it should be considered in conservation schemes and monitoring efforts, further supporting the principle of conserving nature's stage. Yet, differences between habitats and functional groups suggest that more habitat‐specific approaches and multiple biodiversity measures should be considered. Our study is an important signpost guiding further studies on the biodiversity–geodiversity relationship in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

An intensively debated issue in ecology is whether variability in the patterns of diversity of different groups of organisms is congruent in space, a phenomenon referred to as cross‐taxon congruence. Whereas this has been previously mainly tested in terms of taxonomic dissimilarity, the role of ecological processes in determining the congruence of multiple diversity facets (i.e. α‐ and β‐diversity, taxonomic, and functional) remains poorly understood.We used a data set of observation records for 469 macrophyte and 543 fish taxa at the catchment‐scale from the existing literature and data bases to test the existence of multi‐faceted congruence patterns and investigate the variables driving them across 214 catchments covering the whole Chinese mainland.We found cross‐taxon congruence of multiple diversity aspects between fish and macrophyte communities. The energy (i.e. diversity is limited by energy availability), area/environmental heterogeneity (i.e. diversity is higher in larger and more heterogeneous areas), and dispersal (i.e. diversity is driven by dispersal) hypotheses were all significantly attributed to the cross‐taxon congruence, suggesting the existence of key repeated mechanisms underlying assemblage organisation.Our study provides new evidence that can further our understanding of the factors and underlying processes explaining cross‐taxon congruence patterns at broad spatial scales in the freshwater realm, the studies of which significantly lag those in the marine and terrestrial realms. The present findings also provide important baseline information for freshwater conservation initiatives. [ABSTRACT FROM AUTHOR]

Conservation planning has generally used models with a static spatial distribution of species to predict the likely occurrence of species. However, static data do not usually capture rapid changes in the abundance of endangered species or cryptic life stages such as the dormancy stage of eggs and seeds. Little is known about how neglecting dynamic population processes, such as recovery processes, can affect the outcomes of spatial prioritization in conservation planning.In this study, we investigated the distribution of 62 aquatic plant species, including 23 threatened species, in 415 agricultural ponds for 37 years to examine the importance of including recovery processes in conservation planning. Using long‐term historical presence–absence data and seedbank longevity data for aquatic macrophytes, we estimated rates of population disappearance and recovery for each species in each pond over the next 100 years.Average rates of recovery exceeded 0, 0.2, and 0.4 in 85.4%, 40.3%, and 4.8% of aquatic plant species, respectively. Simulation results suggested that the extinction risk for a species greatly decreased when recovery processes were considered. We found that including recovery processes in target species populations increased the performance of spatial prioritization by protecting more species in a smaller number of protected ponds. Spatial ranking of ponds for species conservation differed substantially among scenarios that included and excluded population recovery processes, suggesting that conservation priorities based on complementarity analysis are sensitive to underlying assumptions.Synthesis and applications. Our dynamic approach, which considers recovery processes of species, contributes to more effective conservation planning by reducing bias in the prediction of species' state, given that cryptic life stages are ubiquitous among many plants and some animals. Time‐series presence/absence data on target species are quite useful for the approach and are often archived by participatory monitoring. Thus, the opportunities for applying our method are broad, especially for conservation prioritization and decision‐making at the local scale. Our dynamic approach, which considers recovery processes of species, contributes to more effective conservation planning by reducing bias in the prediction of species' state, given that cryptic life stages are ubiquitous among many plants and some animals. Time‐series presence/absence data on target species are quite useful for the approach and are often archived by participatory monitoring. Thus, the opportunities for applying our method are broad, especially for conservation prioritization and decision‐making at the local scale. [ABSTRACT FROM AUTHOR]

The biodiversity of aquatic ecosystems is under threat and there is an urgent need to quantify the various facets of biodiversity to assess the conservation value of freshwater ecosystems. The effects of taxonomic relatedness have so far not been taken into account in biodiversity assessments of lake macrophytes., We therefore tested the response of species richness and average taxonomic distinctness (Av TD) of aquatic macrophytes along environmental gradients using linear regression models and Bayesian Information Criterion variable selection method. We selected data from four regions, each with 50-60 lakes, situated in northern Europe (Finland and Sweden) and northern America (Minnesota and Wisconsin). We separately studied all macrophyte species, hydrophytes and helophytes., Species richness and Av TD of aquatic macrophytes were generally negatively related in all regions, although it was not statistically significant. Both biodiversity measures responded to environmental gradients to various degrees among the studied macrophyte groups and regions. Species richness was best explained by alkalinity and lake area in Finland, by elevation, annual mean temperature and total phosphorus in Minnesota, and by alkalinity in Wisconsin. Av TD was best explained by alkalinity, annual mean temperature and total phosphorus in Finland and by alkalinity in Wisconsin. Very weak relationships were found in Sweden., Our findings strongly suggest that complementary indices are needed to indicate more comprehensively the effects of environmental conditions on freshwater biodiversity. Species richness was found to be a better measure than Av TD to account for conservation value in freshwaters. However, further research is required to evaluate the usefulness of Av TD to indicate conservation value (e.g. randomisation tests), because alternative measures are clearly needed for those freshwater taxa lacking complete information on true phylogenetic diversity. [ABSTRACT FROM AUTHOR]

Different species' niche breadths in relation to ecological gradients are infrequently examined within the same study and, moreover, species niche breadths have rarely been averaged to account for variation in entire ecological communities. We investigated how average environmental niche breadths (climate, water quality and climate-water quality niches) in aquatic macrophyte communities are related to ecological gradients (latitude, longitude, altitude, species richness and lake area) among four distinct regions (Finland, Sweden and US states of Minnesota and Wisconsin) on two continents. We found that correlations between the three different measures of average niche breadths and ecological gradients varied considerably among the study regions, with average climate and average water quality niche breadth models often showing opposite trends. However, consistent patterns were also found, such as widening of average climate niche breadths and narrowing of average water quality niche breadths of aquatic macrophytes along increasing latitudinal and altitudinal gradients. This result suggests that macrophyte species are generalists in relation to temperature variations at higher latitudes and altitudes, whereas species in southern, lowland lakes are more specialised. In contrast, aquatic macrophytes growing in more southern nutrient-rich lakes were generalists in relation to water quality, while specialist species are adapted to low-productivity conditions and are found in highland lakes. Our results emphasise that species niche breadths should not be studied using only coarse-scale data of species distributions and corresponding environmental conditions, but that investigations on different kinds of niche breadths (e.g., climate vs. local niches) also require finer resolution data at broad spatial extents. [ABSTRACT FROM AUTHOR]

Metacommunity structure may be strongly influenced by spatial dynamics and environmental factors, as well as biogeographic effects. Here, we examined variation in lake cladoceran communities associated with floating macrophytes in the four major Brazilian floodplain systems (Amazônia, Araguaia, Pantanal and Paraná) in relation to local environmental factors, spatial components, climate variables and basin identity., Moran's eigenvector maps were used as a proxy to examine spatial structures within each drainage basin. The final sets of local environmental, climate and spatial variables were selected for constrained ordination models, using a forward selection method. We used variation partitioning to decompose variation in cladoceran community composition in relation to the four sets of predictor variables. Beta-diversity indices were calculated to quantify the contributions of turnover and nestedness components to total beta diversity of cladocerans within each basin and across the basins., Variation partitioning showed that the pure fractions were relatively small, ranging from around zero for spatial and basin identity variables to 2% for climate variables and 4% for local environmental variables. The shared effect of local environmental, climate and basin identity was considerable, accounting for 17% of the total variance. Furthermore, the shared effect of climate and basin identity was also considerable (6%). In total, 32% of variation in cladoceran community structure could be explained by our predictor variables. Cladoceran metacommunities showed high levels of beta diversity attributed to the turnover component, within each floodplain and across all four floodplains., Our finding showed that species sorting was likely to be the main agent structuring cladoceran communities. Spatial processes were not important at very large spatial scales, contrary to what has been found in previous studies. This finding was most likely due to the inclusion of climatic variables in our analysis, combined with the high dispersal ability of cladocerans. [ABSTRACT FROM AUTHOR]

One of the most intriguing questions in current ecology is the extent to which the ecological niches of species are conserved in space and time. Niche conservatism has mostly been studied using coarse-scale data of species' distributions, although it is at the local habitat scales where species' responses to ecological variables primarily take place. We investigated the extent to which niches of aquatic macrophytes are conserved among four study regions (i.e. Finland, Sweden and the US states of Minnesota and Wisconsin) on two continents (i.e. Europe and North America) using data for 11 species common to all the four study areas. We studied how ecological variables (i.e. local, climate and spatial variables) explain variation in the distributions of these common species in the four areas using species distribution modelling. In addition, we examined whether species' niche parameters vary among the study regions. Our results revealed large variation in both species' responses to the studied ecological variables and in species' niche parameters among the areas. We found little evidence for niche conservatism in aquatic macrophytes, though local environmental conditions among the studied areas were largely similar. This suggests that niche shifts, rather than different environmental conditions, were responsible for variable responses of aquatic macrophytes to local ecological variables. Local habitat niches of aquatic macrophytes are mainly driven by variations in local environmental conditions, whereas their climate niches are more or less conserved among regions. This highlights the need to study niche conservatism using local-scale data to better understand whether species' niches are conserved, because different niches (e.g. local versus climate) operating at various scales may show different degrees of conservatism. The extent to which species' niches are truly conserved has wide practical implications, including for instance, predicting changes in species' distributions in response to global change. [ABSTRACT FROM AUTHOR]

Most metacommunity studies have taken a direct mechanistic approach, aiming to model the effects of local and regional processes on local communities within a metacommunity. An alternative approach is to focus on emergent patterns at the metacommunity level through applying the elements of metacommunity structure ( EMS; Oikos, 97, 2002, 237) analysis. The EMS approach has very rarely been applied in the context of a comparative analysis of metacommunity types of main microbial, plant, and animal groups. Furthermore, to our knowledge, no study has associated metacommunity types with their potential ecological correlates in the freshwater realm. We assembled data for 45 freshwater metacommunities, incorporating biologically highly disparate organismal groups (i.e., bacteria, algae, macrophytes, invertebrates, and fish). We first examined ecological correlates (e.g., matrix properties, beta diversity, and average characteristics of a metacommunity, including body size, trophic group, ecosystem type, life form, and dispersal mode) of the three elements of metacommunity structure (i.e., coherence, turnover, and boundary clumping). Second, based on those three elements, we determined which metacommunity types prevailed in freshwater systems and which ecological correlates best discriminated among the observed metacommunity types. We found that the three elements of metacommunity structure were not strongly related to the ecological correlates, except that turnover was positively related to beta diversity. We observed six metacommunity types. The most common were Clementsian and quasi-nested metacommunity types, whereas Random, quasi-Clementsian, Gleasonian, and quasi-Gleasonian types were less common. These six metacommunity types were best discriminated by beta diversity and the first axis of metacommunity ecological traits, ranging from metacommunities of producer organisms occurring in streams to those of large predatory organisms occurring in lakes. Our results showed that focusing on the emergent properties of multiple metacommunities provides information additional to that obtained in studies examining variation in local community structure within a metacommunity. [ABSTRACT FROM AUTHOR]

Patterns of rarity in the context of species richness gradients have intrigued researchers for decades, but the same patterns have only rarely been considered in the context of community composition. There is thus a need to combine the classical rarity theory with expectations from metacommunity research. We studied the responses of assemblages of common and rare lake macrophytes to ecological gradients across various spatial extents. Based on the ideas of metacommunity research, we first hypothesised that the communities of common species are mainly affected by environmental factors and rare species are mainly controlled by spatial processes. Alternatively, following the classical theory of rarity, we expected that common species are environmental generalists (their assemblages are controlled by the spatial processes) and rare species are environmental specialists (their assemblages are controlled by the environment). We used two criteria to define common and rare species: the inflection point criterion and the 50th quartile criterion. Partial redundancy analysis was employed to decompose variation in the assemblage composition of common and rare macrophytes between environmental and spatial variables at each spatial extent and geographical region. Both criteria defined similar sets of common and rare macrophytes across spatial extents. As found in previous studies, the amount of explained variation in the composition of the macrophyte communities along ecological gradients was low overall. However, most of the explained variation, was related to the responses of common species. Assemblage composition of common and rare species was similarly explained by environmental factors. We did not find clear support for current ecological theories with regard to variation in the assemblage composition of common and rare macrophytes. In contrast, our findings suggested that species sorting is collectively structuring the assemblages of both common and rare macrophytes. Spatial variation in metacommunity structuring, however, hinders our ability to draw general conclusions on how common and rare species respond to specific ecological gradients in different regions and at various spatial extents. [ABSTRACT FROM AUTHOR]

Abstract: The correspondence between physical classification schemes and the structure of biological assemblages has been intensively investigated in recent years for the implementation of bioassessment, biomonitoring and conservation programs. We evaluated the effect of temporal variability on the classification strengths of geographically and limnologically delimited regions and of lake connectivity for biological assemblages in a Neotropical floodplain. We sampled several biological groups from lakes in the Upper Paraná River floodplain over two years. Two classification criteria were used, considering (i) lakes associated with three sub-systems (regional scale classification) and (ii) lakes with and without watercourse connections to the river main channel (local scale classification). We directly evaluated the effects of sampling period, sub-systems and connectivity using Permutational Multivariate Analysis of Variance. For the significant factors, we calculated the extent to which the mean within-class similarity exceeded the mean between-class similarity (a measure of classification strength). Finally, we generated classes based on the biological data to evaluate whether they overlapped with the classifications we proposed. The correspondence between the classification criteria and the structures of the assemblages depended on the taxonomic group analyzed. A regional scale classification scheme based on sub-systems was important in accounting for the variability in the structures of different biological assemblages. Connectivity was important only in differentiating macrophyte and zooplankton assemblages. However, temporal variability is an important component affecting the responses of biological assemblages to physical divisions at different spatial scales. In addition, strengths of classifications were generally weak. The a posteriori classifications presented higher strengths of classifications, but also indicated that sub-systems, connectivity and sampling periods are important factors contributing to the variability of different biological assemblages. Further investigations in Neotropical floodplains should also take into account other local factors (e.g., aquatic macrophyte cover) to increase the predictive power of regionalization schemes. [Copyright &y& Elsevier]

Taxonomic distinctness indices are a family of anthropogenic stress indicators that have been used widely in marine ecosystems; however, their utility in freshwater ecosystems is still unclear. We used two taxonomic distinctness indices and species richness to assess relationships between nutrient gradients and three freshwater taxonomic groups, including diatoms, macrophytes and invertebrates. We found that the indices based on the three organismal groups showed generally rather clear relationships with the nutrient levels, indicating that these indices may bring useful additional information for the purposes of bioassessment. However, the two indices describing taxonomic distinctness showed opposite patterns in relation to nutrient levels. The indices for the three groups of organisms were generally poorly correlated with each other, showing that different organismal groups react differently to anthropogenic stress. Accordingly, taxonomic distinctness indices likely tell us about various aspects of nutrient enrichment of freshwater ecosystems. Our findings also emphasized that the value of these indices may be largely dependent on the organismal group used. [ABSTRACT FROM AUTHOR]

• Few broad-scale patterns are well-studied for aquatic macrophytes. • Local environmental predictors were important for freshwater plants at broad-scales. • Several knowledge gaps on macroecology of freshwater plants were identified. • Lack of lotic studies and databases of species traits and phylogeny were found. • Additional macroecological investigations on freshwater plants are clearly needed. Broad-scale studies of species distributions and diversity have contributed to the emergence of general macroecological rules. These rules are typically founded on research using well-known terrestrial taxa as models and it is thus uncertain whether aquatic macrophytes follow these macroecological rules. Our purpose is to draw together available information from broad-scale research on aquatic macrophytes growing in lakes, ponds, wetlands, rivers and streams. We summarize how different macroecological rules fit the patterns shown by freshwater plants at various spatial scales. Finally, we outline future actions which should be taken to advance macroecological research on freshwater plants. Our review suggested that some macroecological patterns are relatively well-evidenced for aquatic macrophytes, whereas little information exists for others. We found, for example, that the species richness-latitude relationship follows a unimodal pattern, and species turnover prevails over species nestedness, whereas higher nestedness-related richness differences are found in low beta diversity regions. Contrary to terrestrial plants, climate or history seem not to be dominant determinants explaining these broad-scale patterns; instead local explanatory variables (e.g., water quality, such as alkalinity and nutrients, and hydromorphology) are often important for freshwater plants. We identified several knowledge gaps related, for example, to a smaller number of studies in lotic habitats, compared with lentic habitats, lack of spatially-adequate aquatic plant studies, deficiency of comprehensive species traits databases for aquatic macrophytes, and absence of a true phylogeny comprising most freshwater plant lineages. We hope this review will encourage the undertaking of additional macroecological investigations on freshwater plants across broad spatial and temporal scales. [ABSTRACT FROM AUTHOR]