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Abstract

The spatial organisation of biotic communities derives from factors operating at a wide range of spatial and temporal scales. Despite strong scientific evidence of prevalent spatial control of community composition in freshwater ecosystems, local environmental factors are often considered as the main drivers of community change. Furthermore, taxonomic approaches are most frequently used, and few studies have compared the relative importance of local and regional control of trait versus the taxonomic composition in stream ecosystems. Using a spatially dense data set covering all stream sizes in a lowland European region of c . 42 000 km ² and three organism groups (macrophytes, macroinvertebrates and fishes), we compared the relative importance of spatial and environmental determinants of species and trait composition in the study streams, classified into headwaters (stream order 1–2) and downstream sites (stream order >2). We hypothesised that (i) there is a higher correspondence between environmental conditions and trait composition than with species composition, (ii) dispersal limitation (pure spatial structuring) is greater in headwaters than in downstream sites and (iii) dispersal limitation (pure spatial structuring) is weakest for macroinvertebrates, intermediate for macrophytes and strongest for fishes. The most consistent pattern across organisms and stream order groups was a higher correspondence between environmental variation and trait composition as well as a higher number of environmental variables significantly related to trait composition than with species composition (hypothesis 1). Spatial structuring peaked in headwater macrophyte communities and downstream fish communities (hypotheses 2 & 3) – a pattern that was amplified when separate analyses of traits describing species dispersal potential were undertaken. Our study highlights the potential of traits to capture multiple environmental changes in stream ecosystems and illustrates how organism‐specific and highly context‐dependent patterns in community organisation can emerge as a consequence of interactions between habitat connectivity (i.e. top versus lower parts of the stream network) and organism dispersal potential.

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... Previous studies have also shown significant advancements in taxonomy-based approach in certain areas, such as improving the efficacy of biomonitoring and biological evaluation (Beck et al. 2013;Hitt and Angermeier 2011;Morse et al. 2007;Wu et al. 2017). However, during recent decades, increasing numbers of studies pointed out some shortcomings of taxonomic approach, including regional independence (Göthe et al. 2017;Heino 2013) and highlighted the need of incorporating functional trait information into biological monitoring and assessment programs (Dolédec et al. 2006;Menezes et al. 2010). Functional traits can be defined as a series of quantifiable biological, ecological, and morphological characteristics that contribute to the adaptive capabilities of taxa in their habitats ). ...
... (2) Traits exhibited by organisms are suggested to allow for comparability of trait-based structures of aquatic communities across regions worldwide (Göthe et al. 2017;Heino et al. 2013). Hence, functional traits show considerable potential to provide a more comprehensive understanding of variations in ecosystem status compared to taxonomic approach (Göthe et al. 2017;Tolonen et al. 2017). ...
... (2) Traits exhibited by organisms are suggested to allow for comparability of trait-based structures of aquatic communities across regions worldwide (Göthe et al. 2017;Heino et al. 2013). Hence, functional traits show considerable potential to provide a more comprehensive understanding of variations in ecosystem status compared to taxonomic approach (Göthe et al. 2017;Tolonen et al. 2017). ...
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Measures based on functional traits are often capable of indicating local environmental conditions and are thus considered promising tools for environmental monitoring and assessment programs. Benthic macroinvertebrates exhibit a diverse array of functional traits that can be used for assessing ecological quality of freshwater ecosystems. However, the associations between functional structure of macroinvertebrates and anthropogenic disturbances remain inadequately understood, especially for floodplain lakes. In our study, we compared the response of taxonomic and functional trait composition of macroinvertebrates to anthropogenic eutrophication in lake ecosystems of the Yangtze River floodplain. We found that the relative abundance of Mollusca, Gastropods, Bithyniidae, Bivalvia and Ephemeroptera showed significant differences among four lake groups (river-connected, macrophyte-dominated, macrophyte-algal transitional and algal-dominated lakes) subjected to different disturbance levels from mesotrophic to highly eutrophic. Using a trait-based approach, we found 13 categories, belonging to seven traits, showed significant differences observed among lake groups. Regarding influence of environmental factors on macroinvertebrate assemblages, both taxonomic measures and functional traits were mainly affected by water quality factors associated with eutrophication. However, the number and specific key environmental factors varied between measures of functional traits and taxonomic composition. The taxonomic composition responded to more environmental factors (seven factors: Chl a, CODmn, TN, area, water depth, NH4⁺-N and conductivity), but showed lower explained variation (24.4%) compared with functional structure (three factors: aquatic vegetation coverage, conductivity and Chl a, 36.4% explained variation). Furthermore, spatial factors only affected taxonomic composition, but they were not correlated with functional composition. In general, our study showed that functional trait structure of macroinvertebrate assemblages responded more sensitively and reliably to eutrophication than measures based on taxonomic composition in floodplain lakes. Thus, we recommend the incorporation of macroinvertebrate functional trait information into biomonitoring programs for floodplain lakes and other aquatic ecosystems, as it can be considered as a more promising approach than taxonomy-based approaches in biomonitoring programs.
... Regional drivers are generally related to dispersal and connectivity between habitats (Astorga et al., 2011;Heino et al., 2003Heino et al., , 2017Mykrä et al., 2007;Sarremejane et al., 2017). Previous studies have frequently found that local drivers of community assembly and structure typically have a greater influence than regional drivers (Heino et al., 2003;Kärnä et al., 2015), although hierarchical assembly can be modulated by an interaction between local and regional factors (Astorga et al., 2011;Göthe et al., 2017;Heino et al., 2017;Murray-Stoker & Murray-Stoker, 2020). At macroecological scales, differences among ecoregions and the composition and diversity of species pools could further contextualize the identity and importance of local and regional drivers on community assembly and structure (Astorga et al., 2011;Heino et al., 2017;Murray-Stoker & Murray-Stoker, 2020). ...
... We identified a link between functional traits and community disequilibrium, but the drivers of functional trait abundance depended on trait category and ecoregion. Dispersal traits were primarily influenced by network variables, which supports previous research documenting spatial influence on communities (Germain et al., 2017;Göthe et al., 2017;Grönroos et al., 2013;Heino & Grönroos, 2014;Horváth et al., 2019;Sarremejane et al., 2017). We found that mean annual flow, a measure of stream size and position within a dendritic network (Altermatt, 2013), was a common predictor of dispersal traits. ...
... It is important to emphasize that longitude and latitude were the most consistent drivers of dispersal traits, which suggests an important role for spatial position within the ecoregional metacommunity. These results suggest a dual influence of habitat amount and spatial configuration on dispersal traits, which follows previous work documenting hierarchical and interactive effects of multiple processes acting simultaneously on local communities (Astorga et al., 2011;Göthe et al., 2017;Heino et al., 2017;Murray-Stoker & Murray-Stoker, 2020). Forested land cover frequently influenced habitat traits, along with impervious surface cover. ...
Article
Aim Metacommunities are assembled through a combination of local and regional processes, with the relative importance of the drivers of assembly depending on ecological context. Global change can alter community assembly at both local and regional levels, potentially shifting communities into disequilibrium with their local environmental conditions. We evaluated the spatial variation in environmental filtering and habitat matching of 1078 riverine macroinvertebrate communities distributed across nine ecoregions. Location Conterminous United States. Taxon Freshwater macroinvertebrates. Methods Patterns in environmental filtering, habitat matching and functional trait diversity were compared among ecoregions. Boosted regression trees were used to identify (1) functional trait predictors of environmental filtering and habitat matching and (2) environmental, landscape and network variables that predict functional trait abundances. Results Environmental filtering but not habitat matching varied strongly by ecoregion. Functional trait diversity varied by ecoregion, but not as strongly as the signatures of environmental filtering. Functional trait predictors of environmental filtering and habitat matching were not consistent, with trait predictors instead varying by individual traits, trait categories and ecoregions. Notwithstanding inconsistent trait predictors, environmental filtering was primarily influenced by habitat preference traits, whereas habitat matching was primarily influenced by both habitat preference and dispersal traits. Predictors of functional traits also varied by trait category and ecoregion, with habitat preference and dispersal traits primarily influenced by network variables. Main conclusions Our study demonstrates the contingent patterns and drivers of environmental filtering and habitat matching on a macroecological scale. We provide the foundation on which trait–environment relationships can be further quantified and causal explanations established in the context of community disequilibrium and applied to conservation and management of freshwater systems.
... Hence, it is necessary to evaluate the relative importance of local environmental filters and regional spatial factors on assemblage patterns. In addition, biodiversity patterns based on taxonomy and functional traits may respond differently to environmental and spatial factors (Gothe et al., 2017;Li et al., 2019b). Studies focused on examining the importance of ecological factors have been conducted in some freshwater ecosystems Li et al., 2019b;He et al., 2020), but very little is known about the relative role of these factors in both the taxonomic and the functional beta diversities of fish along the continuum of a large river. ...
... Hence, the large difference in functional richness among sub-basins led to a high functional beta diversity that was mainly contributed by functional nestedness (84.2%) (Villeger et al., 2013). Consistent with the current understanding of freshwater ecosystems, environmental variables play more important roles than spatial variables for both taxonomic and functional dissimilarities (Gothe et al., 2017;Heino and Tolonen, 2017;Li et al., 2019b). However, functional beta diversity was poorly explained by environmental and spatial variables compared with the taxonomic facet, which was opposite to our expectation that the response of functional traits should be more sensitive to environmental variables (Pollard and Yuan, 2010;Gothe et al., 2017;Li et al., 2019b). ...
... Consistent with the current understanding of freshwater ecosystems, environmental variables play more important roles than spatial variables for both taxonomic and functional dissimilarities (Gothe et al., 2017;Heino and Tolonen, 2017;Li et al., 2019b). However, functional beta diversity was poorly explained by environmental and spatial variables compared with the taxonomic facet, which was opposite to our expectation that the response of functional traits should be more sensitive to environmental variables (Pollard and Yuan, 2010;Gothe et al., 2017;Li et al., 2019b). This finding also occurred in studies of boreal lake benthic invertebrate communities and Tenojoki River organisms (Rocha et al., 2019), which may due to the low level of functional turnover. ...
Article
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Understanding different facets of biodiversity patterns and their ecological drivers are essential for freshwater conservation. This is especially true for fish fauna in the Mekong River, one of the largest rivers in the world, which faces large-scale hydropower development and climate change. Here, we divided the Mekong River into 37 sub-basins to explore the alpha and beta taxonomic and functional diversity of fish fauna and the explanatory power of environmental and spatial factors on fish diversity. We found that species and functional richness varied significantly along environmental gradients, while functional evenness and divergence were weakly correlated with environmental variables. We also found that the high taxonomic beta diversity was mainly contributed by the turnover component, while that of the functional facet was mainly due to the nestedness component. In addition, environmental filtering played a more important role than spatial factors in structuring both taxonomic and functional facets of fish communities. Finally, we found that environmental filtering was more important in determining taxonomic structure than functional structure, which was opposite to the general understanding that functional traits should be better associated with environmental variation. Our study illustrated that functional diversity and taxonomic diversity are complementary ecological indicators when assessing fish diversity of large rivers.
... While sediment granulometry is a key environmental variable for benthic invertebrates, this homogeneity could imply a minor role of environmental control for benthic assemblages in these sections. Some studies performed in European rivers (Göthe et al., 2017;Göthe, Angeler, & Sandin, 2013;Schmera et al., 2018;Tonkin, Heino, Sundermann, Haase, & Jähnig, 2016) suggest that the relative importance of spatial and environmental variables is context dependent. For example, Göthe et al. (2013) found that the role of dispersal and local environmental characteristic as community drivers presented a seasonal variation, entangling the effect of the network position. ...
... Moreover, Schmera et al. (2018) reported such pattern for some taxonomic groups (i.e., benthic invertebrates) but not for other (i.e., fishes). Similar results were also reported by Göthe et al. (2017) for macrophytes. Most of the studies in this regard have been performed in relatively small rivers in the northern hemisphere. ...
... However, it is important to note that our study differs from that of Schmera in that we focused only on non-flying species (Oligochaeta F I G U R E 3 Diagram depicting the proportion of variance in the metacommunity matrix explained by environmental and spatial variables structuring factor of benthic communities peaked in first order streams. Conversely, in a recent study, Göthe et al. (2017) did not find evidence that environmental variables played a more important role in headwaters than in large rivers. ...
Article
The metacommunity theory is a framework that explains the interdependence of local factors and regional processes as community drivers. In rivers, it has been hypothesized that the metacommunity structure and the relative importance of dispersal and local environmental conditions may vary from headwaters toward lowlands. The aims of this study were (1) to analyze the benthic metacommunity structure along the longitudinal dimension of the Paraguay‐Paraná system, and (2) to assess the relative importance of dispersal (spatial structure) and niche‐based processes as drivers of these structures. We used data of oligochaetes assemblages in the studied system and analyzed the Elements of Metacommunity Structure in different river sections. Moreover, we performed a variance partitioning analysis to determine the relative importance of spatial and environmental variables. In the upper section, we found a gradient structure (Gleasonian) and in the lower section we found random and quasi‐Clementsian structures. Similarly, environmental variables were the main structuring factor in the upper section while spatial variables were more important in the delta. The present study provides evidence that metacommunity structure and the underlying mechanisms that shape it, change along the longitudinal dimension of a large South American River. However, we emphasize the necessity of further studies assessing other taxonomic groups and other large South American Rivers.
... Trait responses to specific environmental predictors can be hindered by phylogenetic linkages among traits. To address this issue, we computed trait composition decoupled from the phylogeny using a taxonomic approach (De Bello et al., 2017;Demars et al., 2012;Göthe et al., 2017). This approach must be used to quantify phylogenetic relationships among macroinvertebrates because fully resolved trees are not yet available for this group (Demars et al., 2012;Göthe et al., 2017). ...
... To address this issue, we computed trait composition decoupled from the phylogeny using a taxonomic approach (De Bello et al., 2017;Demars et al., 2012;Göthe et al., 2017). This approach must be used to quantify phylogenetic relationships among macroinvertebrates because fully resolved trees are not yet available for this group (Demars et al., 2012;Göthe et al., 2017). We applied the same approach to the fishes because phylogenetic distances were unavailable for many species in our dataset (e.g. ...
Article
Aim Temperature is regarded as an important driver of broad‐scale biodiversity patterns. However, less is known of the role of dispersal in shaping broad‐scale species and trait distributions, particularly given that species had to disperse out of glacial refugia after the Last Glacial Maximum (LGM). Here, we used a unique dataset describing the distributions of freshwater fauna combined with trait information to evaluate biodiversity relationships to distance to glacial refugia and temperature. Location Twenty‐five biogeographical regions across Europe. Time Period Data from species occurrence were gathered in 1978. Major Taxa Studied A total of 2816 freshwater invertebrate species and 230 freshwater fish species. Methods Using the occurrence of invertebrate and fish species in the biogeographical regions, and publicly available trait information, we analysed patterns in diversity indices (i.e. species richness, trait richness and trait redundancy), trait distribution and species and trait β ‐diversity, and their relationship to distance to known glacial refugia and regional temperature. Results We show that distributions of European invertebrate and fish species and traits are primarily explained by distance to refugia and its covarying effect with temperature (i.e. refugia tend to be warmer). Specifically, species and trait richness were higher in regions proximate to refugia and lower in distant regions. Additionally, communities in colder and distant regions exhibited reduced niche dimensions and slower life histories, suggesting increased vulnerability to environmental change. Main Conclusions Species more distant from their refugia were characterized by higher dispersal capacities. Accordingly, since the LGM, only a subset of species was able to colonize distant regions, while many species have spatial ranges constrained by their dispersal capacity, increasing their potential for extinction under ongoing climate change. Therefore, additional conservation measures considering species' dispersal capacities are required.
... Generally, TDβ is assumed to be more strongly influenced by spatial processes because congeneric species usually possess similar traits, but they might show distinct geographical distribution (Heino et al., 2007). By contrast, environmental factors are assumed to be dominant in regulating FDβ and PDβ, as a result of assumed tight linkages between functional structure and environmental constraints (Göthe et al., 2017;Heino & Tolonen, 2017). ...
... downstream communities (20 sites). The Strahler stream order was used to define headwater (stream order 1-2) and downstream sites (stream order >2) (Göthe et al., 2017), according to a 1:2,500,000 topographic map of the Chishui River basin. ...
Article
Full-text available
1. Disentangling the factors governing community structure across various spatial and temporal scales is a core task in community ecology and biogeography, because it could provide valuable insights into biodiversity conservation and management. The relative role of environmental (a proxy for niche-based mechanism) and spatial (a proxy for dispersal) effects in shaping ecological communities depends on diversity facets, network positions, seasonality and biological characteristics of the focal organisms. However, such patterns are not well understood for fish communities in large river systems, especially if all of these patterns are examined simultaneously. 2. We investigated fish taxonomic, functional and phylogenetic total β-diversity (and their turnover and nestedness phenomena) at different spatial scales (basin vs. section scales) and seasons (wet vs. dry seasons) in a subtropical river system (the Chishui River basin, China). We also quantified the relative importance of environmental variables and spatial factors in shaping fish β-diversity by using generalised dissimilarity modelling. 3. At the basin scale, fish taxonomic and phylogenetic β-diversity across seasons mainly reflected turnover, yet turnover and nestedness contributed likewise to total functional β-diversity. Taxonomic and phylogenetic β-diversity were strongly correlated (r from 0.39 to 0.87), whereas functional and both taxonomic and phylogenetic facets were relatively weakly correlated (r from 0.27 to 0.65). Generalised dissimilarity modelling suggested that phylogenetic β-diversity phenomena were consistently more influenced by environmental variables (wet 16.1%, dry 22.4%) than by spatial factors (wet 6.7%, dry 4.8%). However, for both taxonomic and functional facets, environmental variables (turnover 13.8%, nest-edness 6.4%) and spatial factors (turnover 4.3%, nestedness 9.4%) accounted for a greater proportion of variations in turnover and nestedness, respectively. 4. At the section scale, only phylogenetic total β-diversity and nestedness, as well as taxonomic nestedness significantly differed between the headwater and downstream sections. Furthermore, headwater communities were primarily explained by spatial (15.7%) and environmental (12.7%) variables in the wet season, while
... Vegetation responds to hydrological variables, such as water availability and disturbance events (Hupp and Osterkamp, 1996), whilst also influencing flow, sediment transport, and morphological stability (Gurnell, 2014), meaning that the bi-directional nature of this relationship maps well onto a trait-based framework. Both plant form and distribution have been linked to stream power within the UK (O'Hare et al., 2011), with fluvial conditions also being shown to have a greater influence on trait composition than species composition (Göthe et al., 2017;Corenblit et al., 2015). ...
... Large trees, for example, transition from stabilising banks during maturity to altering channel flow when removed into the river system (Jeffries et al., 2003;Sear et al., 2010). Likewise, the inclusion of layers such as inundation frequency or flow velocity may improve classification approaches, with different traits being dependent on hydraulic and environmental conditions (Göthe et al., 2017;Corenblit et al., 2015). Moreover, both shrubs and grasses are key elements of UK and other temperate river systems, and remote sensing methods will struggle to capture their complexity due to the sensors' limits of detection, currently relying on species identification from imagery. ...
Article
Full-text available
Vegetation plays a critical role in the modulation of fluvial process and morphological evolution. However, adequately capturing the spatial and temporal variability and complexity of vegetation characteristics remains a challenge. Currently, most of the research seeking to address these issues takes place at either the individual plant scale or via larger-scale bulk roughness classifications, with the former typically seeking to characterise vegetation–flow interactions and the latter identifying spatial variation in vegetation types. Herein, we devise a method which extracts functional vegetation traits using UAV (uncrewed aerial vehicle) laser scanning and multispectral imagery and upscale these to reach-scale functional group classifications. Simultaneous monitoring of morphological change is undertaken to identify eco-geomorphic links between different functional groups and the geomorphic response of the system. Identification of four groups from quantitative structural modelling and two further groups from image analysis was achieved and upscaled to reach-scale group classifications with an overall accuracy of 80 %. For each functional group, the directions and magnitudes of geomorphic change were assessed over four time periods, comprising two summers and winters. This research reveals that remote sensing offers a possible solution to the challenges in scaling trait-based approaches for eco-geomorphic research and that future work should investigate how these methods may be applied to different functional groups and to larger areas using airborne laser scanning and satellite imagery datasets.
... Generally, TDβ is assumed to be more strongly influenced by spatial processes because congeneric species usually possess similar traits, but they might show distinct geographical distribution (Heino et al., 2007). By contrast, environmental factors are assumed to be dominant in regulating FDβ and PDβ, as a result of assumed tight linkages between functional structure and environmental constraints (Göthe et al., 2017;Heino & Tolonen, 2017). ...
... downstream communities (20 sites). The Strahler stream order was used to define headwater (stream order 1-2) and downstream sites (stream order >2) (Göthe et al., 2017), according to a 1:2,500,000 topographic map of the Chishui River basin. ...
Article
Disentangling the factors governing community structure across various spatial and temporal scales is a core task in community ecology and biogeography, because it could provide valuable insights into biodiversity conservation and management. The relative role of environmental (a proxy for niche‐based mechanism) and spatial (a proxy for dispersal) effects in shaping ecological communities depends on diversity facets, network positions, seasonality and biological characteristics of the focal organisms. However, such patterns are not well understood for fish communities in large river systems, especially if all of these patterns are examined simultaneously. We investigated fish taxonomic, functional and phylogenetic total β ‐diversity (and their turnover and nestedness phenomena) at different spatial scales (basin vs. section scales) and seasons (wet vs. dry seasons) in a subtropical river system (the Chishui River basin, China). We also quantified the relative importance of environmental variables and spatial factors in shaping fish β ‐diversity by using generalised dissimilarity modelling. At the basin scale, fish taxonomic and phylogenetic β ‐diversity across seasons mainly reflected turnover, yet turnover and nestedness contributed likewise to total functional β ‐diversity. Taxonomic and phylogenetic β ‐diversity were strongly correlated ( r from 0.39 to 0.87), whereas functional and both taxonomic and phylogenetic facets were relatively weakly correlated ( r from 0.27 to 0.65). Generalised dissimilarity modelling suggested that phylogenetic β ‐diversity phenomena were consistently more influenced by environmental variables (wet 16.1%, dry 22.4%) than by spatial factors (wet 6.7%, dry 4.8%). However, for both taxonomic and functional facets, environmental variables (turnover 13.8%, nestedness 6.4%) and spatial factors (turnover 4.3%, nestedness 9.4%) accounted for a greater proportion of variations in turnover and nestedness, respectively. At the section scale, only phylogenetic total β ‐diversity and nestedness, as well as taxonomic nestedness significantly differed between the headwater and downstream sections. Furthermore, headwater communities were primarily explained by spatial (15.7%) and environmental (12.7%) variables in the wet season, while environmental factors (25.9%; spatial 7.7%) dominated in the dry season. By contrast, downstream communities were more influenced by environmental factors (17.9%; spatial 8.3%) in the wet season, whereas environmental (11.0%) and spatial variables (11.5%) contributed likewise to β ‐diversity in the dry season. Our results highlight that, compared with taxonomic β ‐diversity, accounting for turnover and nestedness of functional and phylogenetic β ‐diversity helps to reveal distinct biodiversity patterns, and potential environmental and spatial controls. Given that community–environment relationships and the relative contribution of environmental and spatial factors varied between seasons and between the basin and section scales, our study underlines the importance of long‐term dynamics and spatial scales in metacommunity studies. Our findings also suggest that maintaining environmental heterogeneity and adequate hydrological connectivity would be essential for the conservation of fish diversity. Overall, our study advances current knowledge of fish biodiversity patterns and their maintenance mechanisms by adding insights from multi‐faceted diversity and seasonality, which has rarely been done in large subtropical rivers.
... Thus, macrophyte communities are a fundamental component of rivers that respond to both anthropogenic and natural disturbances. In addition to species composition, plant trait composition can show strong linkages with environmental changes [16][17][18][19]. For instance, macrophytes show a variety of growth forms that reflect adaptations to their physical habitat with various implications on ecosystem processes [20]. ...
... Trait responses to eutrophication have been documented in several studies [38,39], indicating that functional composition can be used to examine the response of communities to environmental problems. As a result of the increased interest in the potential use of functional diversity and trait composition in ecological monitoring and river management, there is a growing number of studies that investigate various aspects of the trait distribution and/or the functional diversity of macrophyte communities across environmental gradients [16,28,39,40]. ...
Article
Full-text available
The analysis of plant trait composition has raised significant interest among freshwater ecologists as a complementary approach for assessing the effects of environmental change on ecosystem functions. In this study, we investigated patterns of functional traits of the aquatic macrophyte assemblages of 74 lotic ecosystems of Greece, and we identified associations between species traits and environmental variables (hydromorphological and physicochemical parameters) through testing the hypothesis that the environmental features determine the spatial structure of traits. We allocated 12 traits to a total of 39 hydrophyte species, and we conducted RLQ and fourth corner analysis to explore relationships between species, trait composition, and environmental gradients. Based on the results of the RLQ, a hierarchical cluster analysis was conducted to identify groups of plants that share common trait characteristics. Plants were discriminated into five discrete groups based mostly on their life form (e.g., free-floating, rooted submerged etc.) and their ecological preference for nitrogen levels. Hydromorphological parameters had a higher contribution than physicochemical variables in explaining the total variance of the trait data, with water abstraction, channel substrate, and hydrologic alteration being the most important. Our analysis did not reveal significant bivari-ate relationships between single traits and environmental parameters, although the five groups of macrophyte assemblages appeared to associate with certain environmental gradients. Free-floating and emergent plants were related to higher concentrations of nutrients, whereas rooted submerged plants were related to higher oxygen concentration and increased pH. In addition, free-floating plants were highly associated with metrics of hydromorphological change. Our findings showed clear discrimination of macrophytes based on their functional composition and association of traits with environmental gradients. Thus, further research could explore whether macrophyte functional groups can serve as indicators of environmental change and the overall ecosystem health.
... In addition to the influence of dispersal on the structure of fish assemblages, environmental filtering is also expected to control fish diversity (Poff 1997;Carvalho and Tejerina-Garro 2015;Zbinden and Matthews 2017). Indeed, there is a vast body of literature illustrating the association of fish species and their traits to environmental factors in headwater habitats (e.g., Pease et al. 2012;Tejerina-Garro 2015, 2018;Ribeiro et al. 2016;Göthe et al. 2017;Rodrigues-Filho et al. 2017;Zbinden et al. 2022). Additionally, the relative isolation of headwater streams associated with harsh environmental conditions would promote differentiation among fish assemblages according to dispersal and niche selection (Finn et al. 2011;Green et al. 2022). ...
... Moreover, we observed that elevation and channel width were positively associated with functional diversity, whereas water conductivity was negatively associated with this parameter. The correspondence of an elevated number of environmental variables and traits, as observed in our results, seems to be a consistent pattern across different groups of stream aquatic organisms (Göthe et al. 2017). Both elevation and water conductivity can drive the occurrence of different fish functional traits in headwater streams, whereas channel width drives the occurrence of different traits between a river and headwater habitats (Carvalho and Tejerina-Garro 2018). ...
Article
The aim of this investigation was to determine whether fish diversity in headwater streams is influenced by environment, connectivity with large rivers via source-sink dynamics, and/or by an interchange of individuals with other stream assemblages. We measured local diversity using four indices: species richness (SR), functional diversity (FD), taxonomic diversity (TD), and local contribution to beta diversity (LCBD). For each descriptor, we applied a variation partitioning framework based on a partial linear regression, considering environmental variables and distance of headwater streams to the mainstem or pairwise distance among streams as predictors. The results indicated that water velocity was positively associated with SR, while FD is positively associated with elevation and channel width, and negatively with conductivity. All diversity indices were significantly associated with distance among streams. SR and TD were both related to spatial filters describing larger scales, while FD was related to smaller scales, and LCBD was related to both smaller and larger scales. These results indicate that differences in SR and TD are greater among distant assemblages, whereas FD and LCBD respond to an interplay between local and regional processes. The variation of the four indices was also explained by the shared component between environment and space but not by the distance of headwater streams to the main stem. Therefore, patterns of local fish diversity seem to be more related to patch dynamics or species sorting, rather than to source-sink dynamics. Strategies to protect assemblages of headwater streams in tropical regions should consider multiple sites rather than single sites to guarantee species dispersal and the preservation of environmental heterogeneity.
... The community structure of fish at the macro-habitat scale is mostly influenced by geographical and land-use patterns (Sarkar & Bain, 2007). Studies on the relative importance of local environmental drivers and spatial determinants in structuring the community composition of riverine fishes are gaining attention in different regions of the world, especially in temperate (e.g., Cilleros et al., 2017;Gothe et al., 2017) and subtropical river ecosystems (Lopez-Delgado et al., 2020;Mondal & Bhat, 2022;Shukla & Bhat, 2018). However, there is still a major knowledge gap for afro-tropical river ecosystems. ...
... Our results of spatially structured fish communities in the LNRB partly correspond to Drakou et al. (2009) and Gothe et al. (2017) who reported a strong correspondence between fish community composition and spatial factors in a temperate freshwater system. hence enhances dispersal of fish. ...
Article
We investigated the relative influence of local environmental and spatial factors in structuring the community composition of fish at 15 sampling sites along the longitudinal gradient of the Lower Niger River Basin (LNRB) in dry and rainy seasons using distance-based redundancy analysis and variation partitioning analysis. We collected a total of 3807 fish specimens representing 42 species. Our result indicated that the fish community composition differed between the upper and lower regions of the river. The communities in the upper region is influenced by high-nutrient concentrations, while downstream sites were characterized by high concentrations of suspended solids. Variation partitioning revealed higher contributions of spatial than environmental predictors on fish community composition, with a higher total predicted variance in dry season. The variations in the community composition between upper and lower region may be attributable to the differences in the nature of anthropogenic activities within the regions, which influenced the local conditions differently. Differences in flow dynamics between upper and lower regions as attributable to black and white floods in the LNRB modify the connectivity between sites. Dispersal among sites may be more limited downstream than in the upper region, particularly in the dry season, because damming in the upper region also interrupts the natural flood regime such that there are low water levels in the lower region, which spatially isolate fish communities at certain sampling sites. The relatively higher total predicted variance during dry season may be attributable to the temporal differences in abiotic conditions between sites, which may have influenced site level community composition and abundance differently.
... Due to their ecological importance, macrophyte species are formally recognized as one out of four biological quality elements used in the monitoring of surface water ecosystems [15]. Macrophyte communities are strongly influenced by hydrology, reflecting both anthropogenic and natural disturbances, with hydrology having a stronger effect on the trait composition than on the species composition of the community [16][17][18][19]. ...
... There is a growing body of literature dealing with the relationships between environmental factors and functional diversity and trait distributions of macrophyte communities in altered waterbodies (e.g., [4][5][6][13][14][15][16][17][18][20][21][22][23]). The methods applied to investigate these relationships include the use of multivariate characterization of functional assemblage structures, functional diversity measures, and/or specific trait-environment correlations. ...
Article
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There is a gap in the knowledge about how environmental factors affect functional diversity and trait structures of macrophyte communities in altered waterbodies. We used macrophyte and environmental data collected from 46 waterbodies; we extracted data on 14 traits with 43 attributes for 59 species and calculated seven functional diversity indices. We used redundancy analysis (RDA) to investigate the response of functional diversity indices to the environmental variables. To relate traits to environment we performed the analysis on three data matrices: site by environmental variables (R), site by species (L), and species by traits (Q)-the RLQ analysis, and the 4th corner analyses. The RDA showed that the environmental variables explained 47.43% of the variability in the functional diversity indices. Elevation, hemeroby (integrative measure of the impact of all human intervention) of the land cover classes on the banks, and water conductivity were correlated with all diversity indices. We found that the traits characteristic of floating and emergent plants represents a strategy to increase efficiency in light interception under high nutrient concentrations in lowland waterbodies, while submerged plants dominate nutrient-poorer waterbodies at higher altitudes. Future investigations should be focused on the role of functional diversity and the structure of macrophyte communities in the indication of tradeoffs and/or facilitation between ecosystem services that altered waterbodies provide, in order to guide their adequate management.
... Traits-based approaches are well suited for eco-geomorphic research due to the strong environmental gradients within fluvial systems (Naiman et al., 2005). Vegetation responds to hydrological variables, such as water availability and disturbance events (Hupp and Osterkamp, 1996) whilst also influencing flow, sediment transport, and morphological stability (Gurnell, 2014), are all key controllers of trait composition, with the environmental conditions better related to trait, rather than species, composition (Göthe et al., 2017). Furthermore, individual species have been shown to demonstrate differing traits depending on external stresses. ...
... meaning that the bi-directional nature of this relationship maps well onto a traits-based framework.O'Hare et al. (2016) have assessed the traits of nearly 500 species that influence river processes, revealing evidence of a broad link between plant form, distribution, and stream power within the UK(O'hare et al., 2011). Moreover, traits-based approaches allow for a more comprehensive view on eco-geomorphic interactions than a purely taxonomic approach due to the environmental conditions having a larger influence on trait compositions than species compositions(Corenblit et al., 2015;Göthe et al., 2017).To date, the majority of traits-based research has focussed on ecological responses to hydrological conditions. For example, inundation likelihood has been shown to increase the presence of plants with longer and younger leaves(Stromberg and Merritt, 2016;McCoy- Sulentic et al., 2017) whilst also being less woody(Kyle and Leishman, 2009;Stromberg and Merritt, 2016), with frequent inundation and higher stress environment necessitating greater flexibility. ...
Thesis
The importance of vegetation within the fluvial domain is well established, influencing both flow and morphology, and has long been recognised as a key component of the river corridor. Despite this, adequately capturing the spatial and structural variability of vegetation for us to understand the eco-geomorphic feedbacks occurring at a range of scales remains a challenge. Currently, the focus of this research takes place at either the individual plant scale, looking into vegetation-flow interactions, or at larger scales, attempting to spatially discretise vegetation for bulk roughness metrics. Subsequently, hydrodynamic models are typically based around these bulk roughness values which exclude vegetation structure. The aim of this research is to attempt to bridge this gap and link the different scales of analysis to improve our understanding of eco-geomorphic interactions. This is achieved by: (1) Examining current remote sensing methods that may be used for fluvial research, (2) Developing a novel UAV based remote sensing system to collect plant scale data for reach scale analysis, (3) Extracting trait-based metrics for individual plants and upscaling these to reach scale extents, (4) Implementing these traits-based parameters in to a 2D hydrodynamic model. At present, the main trade offs in remote sensing centre around scale and resolution, whereby capturing larger areas reduces the detail of the phenomena being studied. Structure from Motion (SfM) photogrammetry has helped to bridge this gap yet fails to reconstruct topography in vegetated reaches and cannot resolve vegetation structure. These drawbacks have herein been overcome with the introduction of UAV based laser scanning techniques, capable of accurately capturing topography in vegetated reaches as well as resolving vegetation structure. This data can be used to extract traits-based vegetation metrics, identify individual guilds within a river corridor, and be scaled to spatially discretise vegetation structure at reach scales. Guilds are then evaluated against monitored morphological change to investigate eco-geomorphic feedbacks. These vegetation metrics and classifications are subsequently used to parameterise a 2D hydrodynamic model, showing the impact that vegetation discretisation methods have on model outputs. This research has developed methods for obtaining reach scale data on vegetation structure to better inform our understanding of eco-geomorphic feedbacks. The robustness and scalability of these methods presents future avenues of research, both within the fluvial domain and for other environmental research applications, where eco-geomorphic feedbacks have a major influence in shaping the Earth’s surface.
... The process was conjectured to mainly result from mass effects closely associated with high dispersal rates. This mechanism has been shown to emerge in aquatic ecosystems with high hydrological connectivity, including lakes (Janzen et al. 2017;Jiang et al. 2020) and river mainstems (Göthe et al. 2017;Vardakas et al. 2020). Some previous studies, focusing on aquatic organisms, such as macrophytes ) and macroinvertebrates (Cai et al. 2017), supported that spatial process is the main driving force in structuring lacustrine metacommunity. ...
... The revelation of seasonal changes in fish community assembly mechanisms of Lake Dongting in this study has several implications for bio-conservation. Environmental filtering functions in structuring the fish community of Lake Dongting in the non-flooding season, as found in other riverine environments (Giam and Olden 2016;Göthe et al. 2017). This process becomes stronger in the dry season when the lake transforms into riverine facies. ...
Article
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Although environmental filtering and spatial structuring are commonly regarded as two key factors shaping community dynamics, their relative contribution remains unknown for numerous aquatic ecosystems, particularly highly dynamic floodplain lakes. This issue is here addressed by examining the seasonal metacommunity dynamics of freshwater fishes in Lake Dongting, a large subtropical lake of the middle Chang-Jiang basin in southern China. Physicochemical variables and fish assemblages were recorded at 20 sampling sites during the wet, normal and dry seasons. Distance-based redundancy analysis and associated variation partitioning were used to examine the relative role of environmental variables and spatial factors in fish community assembly in each season. Analysis results demonstrated that the relative contribution of environmental filtering and spatial structuring varied depending on environmental features and the extent of hydrological connectivity in different seasons. Intensified physicochemical parameters in the dry season convinced the enhanced environmental filtering; whereas high hydrological connectivity in the wet season favored the stronger spatial process. Specifically, the community assembly processes were temporally dynamic; spatial structuring (or mass effects), resulting from excessively high dispersal rates, was dominant during the flooding season, environmental filtering was stronger than spatial structuring (or dispersal limitation) during the non-flooding season. These findings highlight the importance of conserving local habitats of Lake Dongting during the dry and normal season, and maintaining of the flood pulse of the lake and its natural variability during the wet season. Apparently, the construction of a water-level regulation project at the Chenglingji Channel, the outlet watercourse of Lake Dongting, is not supported because it will change the flood pulse of this lake and thus impact habitat heterogeneity or variability.
... Thus, macrophyte communities are a fundamental component of rivers that respond to both anthropogenic and natural disturbances. In addition to species composition, plant trait composition can show strong linkages with environmental changes [16][17][18][19]. For instance, macrophytes show a variety of growth forms that reflect adaptations to their physical habitat with various implications on ecosystem processes [20]. ...
... Trait responses to eutrophication have been documented in several studies [38,39], indicating that functional composition can be used to examine the response of communities to environmental problems. As a result of the increased interest in the potential use of functional diversity and trait composition in ecological monitoring and river management, there is a growing number of studies that investigate various aspects of the trait distribution and/or the functional diversity of macrophyte communities across environmental gradients [16,28,39,40]. ...
Research Proposal
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Dear Colleagues, The Diversity Journal is ready to launch a Special Issue dedicated to Aquatic Plant Diversity, Conservation, and Restoration. You are cordially invited to prepare a scientific paper for this Special Issue. Freshwater biodiversity loss continues at an alarmingly fast rate, and the loss of diversity and ecological functions of aquatic plants (macrophytes) continues. There’s urgency to better understand the ecology of freshwater macrophyte communities worldwide to best serve conservation and resilience, mitigate further diversity loss, and restore degraded habitats. In this Special issue, we will: • Highlight the magnificent biodiversity of macrophytes globally in a variety of freshwater habitats, which are elusive to most people because many species live underwater or in remote habitats. • Cover all aspects of macrophyte diversity, including at the organismal-level (genetics, within populations, and functional traits) and the community-level (alpha, beta, and gamma diversity metrics; phylogenetics) • Showcase meta-analyses and generalizable case studies that describe the patterns and processes of macrophyte biodiversity, community change, vulnerability, and resilience. • Emphasize the needs and opportunities for macrophyte conservation and restoration. Papers may either evaluate specific restoration actions (e.g., hydrologic and connectivity engineering, plantings, habitat improvements, invasive species control, or novel techniques), or, discuss how the ecological knowledge gained may be applied to conservation or restoration. Thank you for your important contributions to this field of study, and thanks in advance for considering a submission to this upcoming Special Issue. Sincerely, Dr. Danelle M. Larson, Dr. Eva Papastergiadou Guest Editors
... The establishment and structure of macrophyte communities in rivers are largely determined by physical factors (i.e., water current, light availability, bottom substrate) that combine the effects of water and sediment chemistry on community composition (Butcher, 1933;Canfield and Hoyer, 1988;Baattrup-Pedersen and Riis, 1999;Riis et al., 2001;Riis and Biggs, 2003;Daniel et al., 2006;Janauer et al., 2010;O'Hare et al., 2010;Steffen et al., 2013). Macrophyte communities are strongly influenced by river hydrology, reflecting both anthropogenic and natural disturbances, where these environmental factors have stronger effect on the trait composition than on the species composition of the community (Papastergiadou et al., 2016;Göthe et al., 2017;Baattrup-Pedersen et al., 2018;Bejarano et al., 2018). Due to the great potential that functional diversity and trait composition of macrophyte communities might have in bioindication of hydro-morphological disturbances in running water-bodies, and its potential importance in river management, there is a growing number of studies investigating the influence of these factors on the trait distribution and/or functional diversity of macrophyte communities (e.g., Baattrup-Pedersen et al., 2016;Göthe et al., 2017;Lukács et al., 2019;Manolaki et al., 2020;Paz et al., 2021;Stefanidis et al., 2021). ...
... Macrophyte communities are strongly influenced by river hydrology, reflecting both anthropogenic and natural disturbances, where these environmental factors have stronger effect on the trait composition than on the species composition of the community (Papastergiadou et al., 2016;Göthe et al., 2017;Baattrup-Pedersen et al., 2018;Bejarano et al., 2018). Due to the great potential that functional diversity and trait composition of macrophyte communities might have in bioindication of hydro-morphological disturbances in running water-bodies, and its potential importance in river management, there is a growing number of studies investigating the influence of these factors on the trait distribution and/or functional diversity of macrophyte communities (e.g., Baattrup-Pedersen et al., 2016;Göthe et al., 2017;Lukács et al., 2019;Manolaki et al., 2020;Paz et al., 2021;Stefanidis et al., 2021). However, there is still a lack of data on the effects that hydro-morphological disturbances have on the functional diversity and trait composition of macrophyte communities in a large, heavily modified river, such as Danube. ...
Article
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Macrophyte communities have major role in the functioning of freshwater ecosystems. However, there is gap in knowledge about how natural and anthropogenic hydro-morphological disturbances affect their functional diversity and trait structure, particularly in the temperate large rivers. In this study we investigated the effect of hydro-morphology on functional diversity and trait structure of macrophyte communities in the middle section of the Danube course. We collected macrophyte and environmental data from 947 sampling units in the main river channel and connected side waterbodies. We extracted data on 18 traits with 65 trait states and calculated seven functional diversity metrics and cumulative weighted means of trait states (CWMs). We applied redundancy analysis (RDA) to investigate the response of functional diversity metrics to the environmental variables, and Variation Partitioning to determine whether natural, or anthropogenic subset of hydro-morphological factors is more important predictor of functional diversity. To relate CWMs and environmental variables, we performed RLQ and fourth-corner analysis, followed by false discovery rate procedure. Hydro-morphological variables explained 36.7% of the variability in the functional diversity metrics. Combined effect of two subsets of environmental variables explained largest part of the variability in functional diversity metrics. Six associations between traits and environmental variables were found. We found that functional diversity metrics indicate prevailing ecological processes, from environmental to biotic filtering, along the natural—anthropogenic hydro-morphological gradient. We concluded that functional diversity metrics are potentially useful tools in the identification of the causes of ecological degradation, and could be applied in river bioassessments and management.
... Most previous studies based on the network position hypothesis distinguished headwater streams from mainstem or downstream rivers according to Strahler (1957) order or catchment size (Brown and Swan 2010, Tonkin et al. 2015, Göthe et al. 2017), but another type of small stream has rarely been considered. In the periphery of river networks, low-order streams (i.e., headwater streams) converge hierarchically into mainstem rivers, whereas farther down the network, small (i.e., adventitious) streams can flow directly into mainstem rivers (Grant et al. 2007). ...
... These differences between the 2 stream types might represent different models of metacommunity structuring. It is possible that, with relatively low dispersal, species composition can track variation in local environmental conditions via species sorting (Leibold et al. 2004), whereas more frequent species dispersal (i.e., mass effects) in highly connected streams can mask the potential influence of environmental selection (Ng et al. 2009, Göthe et al. 2017. In another view, the variation in metacommunity processes also depends on the size of the species pool Myers 2011, Meynard et al. 2013). ...
... Although there are similar classifications based on several attributes to infer the dispersal capacity of fish, such as Olden et al. (2008) and Göthe et al. (2017), information on Amazonian fish species is still very incomplete (Rodrigues-Filho et al. 2018a). Due to the scarcity and lack of such information, we proposed the following general criteria for species classification: (i) high dispersal capacity: presence of constant swimming in the water column, inhabits variable flow conditions and generalist for microhabitat and (ii) low dispersal capacity: the presence of parental care, territorial behavior, substrate association, burying habits, are usually associated with one or more specific microhabitats. ...
... The fish group with high dispersal capacity was influenced by local environmental variables of substrate (% fine gravel) and channel morphology (wetted width and thalweg depth), in agreement with several studies (Couto and Aquino 2011;Roa-Fuentes and Casatti 2017;Zbinden and Matthews 2017), but was also influenced by the distance between streams (PCNM1). Considering that the first PCNM vectors explain spatial relationships occurring at larger scales (Göthe et al. 2017;Vilmi et al. 2017), this effect for the group indicates a possible dispersal limitation because the greater the distance between sites, the stronger the limitation (Logue et al. 2011;Heino et al. 2015). This was also evidenced in the results of the variation partitioning, suggesting that both species sorting and spatial processes can help explain the structure of local communities. ...
Article
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Separating species in terms of dispersal capacity can be useful to understand how local and regional factors affect the distribution of organisms in metacommunities. In this study, we sought to unravel how the characteristics of local habitats and spatial distances structure fish communities in Amazonian streams. We hypothesized that fishes classified with high dispersal capacity are mainly structured by mass effects and respond to environmental and spatial variables in the same proportion, while fishes classified with low dispersal capacity are mainly structured by species sorting, responding mainly to local environmental variables. We collected fish from 36 well-preserved streams in the Capim river basin in northern Brazil during the dry season. In general, the community composition was structured by characteristics of the local habitat. Spatial variables influenced each group at different intensities, agreeing with the models of species sorting and mass effects and corroborating our hypotheses. Thus, our findings suggest that the dispersal mode affects how metacommunities are structured. The differences in the patterns observed between the groups compared can help in the management and conservation of species, such as those with greater environmental requirements and more susceptible to habitat changes. We emphasize the need to maintain habitat integrity and connectivity in headwater streams to conserve species in their habitats.
... On the other hand, environmental variables solely or mainly structured community composition of river plants in Finland (Alahuhta et al., 2015) and in Canada (Bourgeois et al., 2016). Variation in lowland river plant communities was similarly explained by only local environment, whereas both the environment and space contributed to variation in headwater river plant communities in Denmark (Göthe et al., 2017). These few and rather contradictory findings highlight the need for further research to examine the relative roles of environmental filtering and spatial processes on river plant communities. ...
... Of the categorical divisions, the functional groups based on life form have probably been the most used (e.g., Chappuis et al., 2012;Mormul et al., 2015;García-Girón et al., 2018). More recently, species traits have been utilized in broad-scale studies without categorical divisions of trait composition, but instead using continuous or experimentally quantified values (e.g., Göthe et al., 2017;Iversen et al., 2019). Over the last few decades, research has focused on several morphological, physiological and life-history traits that are related to plant morphology and hydrology, perennation (i.e., a species growing for a single or several years), use of carbon, photosynthetic efficiency, and dispersal vectors (e.g., De Wilde et al., 2014;Fu et al., 2014;García-Girón et al., 2019a, b, 2020aIversen et al., 2019;Lindholm et al., 2020a, b). ...
Article
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.
... VS geomorphology and RS hydrology variables were strong predictors of fish assemblage variation using functional traits and taxonomy. This was unexpected as functional trait analyses frequently find stronger relationships for environmental variability than from taxonomic analyses (Göthe et al., 2017;Pease et al., 2012;Poff & Allan, 1995), likely due to closer connections to ecosystem functions. Our results were unable to confirm that fish distributions are products of their functional traits, even at larger scales (Lamouroux et al., 2002;Poff & Allan, 1995). ...
Article
Fish assemblages, defined by taxonomy or functional traits, –respond to regional and local habitat variation. Our hypothesis was that fish assemblages could be best predicted using reach‐scale (RS) hydrology variables over valley‐scale (VS) hydrogeomorphology variables for US and Mongolian rivers. We further predicted that fish traits were predicted better by RS than VS variables. We evaluated the FS and VS hydrogeomorphologies of rivers in the United States and Mongolia in each of three ecoregions: grassland, forest and endorheic. Fishes were collected using a backpack electrofisher, following standard protocols. Constrained ordination analyses were conducted at three scales: among continents, by continents and by individual ecoregions within continents. We found no significant difference in mean variation explained by VS versus RS or by taxonomy versus traits. Ecoregions differed in factors contributing to fish assemblage patterns, likely a result of differences in hydrogeomorphology, hydrological connectivity and historical influences. We found that fish assemblages were structured by hydrogeomorphic processes occurring at VS and RS, and that variables predicting fish assemblages varied with scale and whether fishes were classified by taxonomy or traits. Although anthropogenic impacts were substantially higher for western US rivers than for Mongolian rivers, we were unable to detect strong differences in our ability to predict fish assemblage variation from RS and VS habitat variables.
... At smaller spatial scales, our study also observed weak dispersal limitations (Soininen, 2012), with Achnanthidium delmontii being the dominant species throughout the watershed and belonging to nested species. Normally, the downstream dispersal limitations will be less due to better connectivity (Demars and Harper, 2005;Gothe et al., 2017), and even among the idiosyncratic species, the dominant species in both the mid-and downstream was Melosira varians in the TIL. Weak dispersal limitation represents greater ability to exchange individuals between sampling sites, and the more obvious the homogeneity of the communities (Lopes et al., 2014). ...
Article
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Insight into the non-random distribution patterns of species in different regions is a foundational aim of research in community ecology and biogeography. The nestedness pattern, which investigates changes in species composition and abundance, has been widely used in numerous studies. However, studies on the nestedness of benthic diatoms are extremely rare, and consequently little has been mentioned of their assemblage mechanisms. To fill this gap, based on 168 benthic diatom species from 147 sampling sites in the Thousand Island Lake (TIL) catchment, we calculated their nestedness and niche width with the aim of i) analyzing the nestedness of benthic diatoms communities with different attachment abilities in TIL; ii) calculating niche width differences between nested and idiosyncratic species with different attachment abilities; iii) investigating the differences in alpha and beta diversity between nested and idiosyncratic sites; iv) examining whether environmental variables influencing the nestedness of benthic diatom communities are dependent on attachment ability. The results demonstrated a significant nestedness pattern in the benthic diatom metacommunity, and the sampling sites of low attachment species not only exhibited a nestedness pattern, but also with a lower nestedness value compared to the sampling sites of all species. Nested and idiosyncratic species differed in niche width, whereas differences between nested and idiosyncratic species of low attachment species were smaller. Additionally, significant differences in alpha and beta diversity were observed between nested and idiosyncratic sites. Furthermore, it was revealed that the nestedness of benthic diatom metacommunity in our study area were mostly influenced by local environmental variables. Our study contributes to the understanding of the significant nestedness observed in benthic diatom metacommunity in TIL, highlighting its relevance to biodiversity conservation efforts.
... The fourth-corner test was used in this study to highlight the relationship between environmental predictors and ecological preferences in the EPT group. Much attention has been given to the application of the trait approach, which may provide a better tool for a combination of instream stressors than classical taxonomic-based indices (Menezes et al. 2010;Göthe et al. 2017Edegbene et al. 2020b, Edegbene et al. 2021bEdegbene et al. 2023). ...
Article
Spatial pattern comprehension, dynamism of energy, and transfer of matter in running freshwater systems are significant for the functional composition of aquatic communities. Recently, the trait-based approach has become the center of functional assessment. The trait-based approach can complement structural bioassessment tools and has the advantage of combining ecological features and biological characteristics rather than only the use of a taxonomic-based approach. In the current study, we explored the differential responses of EPT (Ephemeroptera, Plecoptera, and Trichoptera) traits in selected stream sites in the northwestern Rif of Morocco. A Surber sampler with a 500-µm mesh size and dimensions of 20 × 20 cm was used to collect EPT samples at the sites. Physicochemical and hydromorphological parameters, including temperature, pH, BOD 5 , NO-3 , Cl − , depth, and current velocity, were used to characterize the water quality of the sampled sites. We used 54 trait modalities belonging to 11 trait classes to describe the collected EPT at the family level. We conducted RLQ model and fourth-corner test to examine the interaction between the EPT traits assemblage and habitat predictors at the 36 sampled sites along the stretch of the study area. The RLQ ordination revealed that the distribution patterns of EPT traits differed significantly over the 36 sites. Thus, we expected that the EPT traits assemblage would reflect the degree of the detected environmental pressures. The RLQ model indicated that elevated nutrient levels and conductivity were the key factors explaining most of the variability in functional traits at the downstream sampled sites. EPT traits such as life cycle duration, food preferences, maximal potential size, and substrate preference were positively associated with sites exhibiting notable deterioration. Baetidae and Leptophlebidae in S2, S3, and S20 favored these trait assemblages. The fourth-corner test revealed that there was no statistically significant difference in the relationship between the EPT traits and selected physicochemi-cal and hydromorphological parameters.
... In comparison with the taxonomic structure, trait-based composition of assemblages typically exhibits a stronger correlation with environmental stressors, thus responding more reliably to environmental gradients (Villéger et al. 2008). Incorporating functional approaches in biomonitoring can offer several additional advantages, e.g., broad region applicability due to a global consistency in the expression of traits across most fauna (Heino 2011;Göthe et al. 2017) and serving as indicators of ecosystem functions (Gravel et al. 2016). Therefore, incorporating functional approaches can aid in identifying the causes of ecosystem impairment and provide insights into the specific ecosystem functions impacted by anthropogenic disturbances (Feio and Dolédec 2012). ...
Article
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Functional trait measures have the potential to represent local habitat conditions and are considered promising tools for biomonitoring and bioassessment programs. Macroinvertebrates are an ecologically significant group in freshwater ecosystems and possess a range of functional traits which are employed to assess ecological quality. Nevertheless, the relationships between macroinvertebrate functional structure and anthropogenic disturbances remain poorly understood. In this study, we conducted a comparison of how functional trait-based and taxonomy-based composition of macroinvertebrate assemblages responded to eutrophication in Lake Taihu, a typical large eutrophic freshwater lake in China. Specifically, we examined both the taxonomy-based and trait-based compositions of benthic macroinvertebrates varied along the eutrophication gradient. Eutrophication was associated with remarkable decreases in the abundance of gastropod taxa and increases in Oligochaeta and Chironomidae. Ten categories belonging to six traits were significantly different among three site groups. The eutrophic and transition sites showed higher abundance of Size2, burrowers, and integument-respiration organisms than macrophytic sites, whereas abundance of Size1, conical-shaped, sprawlers, scrapers, and lung-respiration were higher in macrophytic sites. Both taxonomic (36.8%) and functional compositions (39.8%) of macroinvertebrate assemblages were influenced by the same variables: CODMn and transparency. Our study showed that macroinvertebrate trait-based approaches can be considered a useful supplement to traditional taxonomic approach for biomonitoring programs in freshwater lakes.
... Please resupply the figures in a resolution of at least 300 dpi Introduction Understanding how local communities are assembled from regional species pools and how the processes vary across spatial scale has been a key issue in community ecology (Márquez and Kolasa 2013). While environmental controls on species coexistence have been studied extensively for individual local communities (Bernard-Verdier et al. 2012, Myers et al. 2013, Fu et al. 2014, Püttker et al. 2015, Göthe et al. 2016, the potential dispersal role originating from a set of interacting local communities (metacommunity) within a region has attracted much attention (Grönroos et al. 2013, Heino et al. 2015a, Gianuca et al. 2017, Heino et al. 2017a, García-Girón et al. 2020. The metacommunity framework has emerged as a fundamental theoretical basis for understanding how the links between dispersal, environmental factors, and species interactions determine the regional coexistence of species within landscapes (Leibold et al. 2004). ...
Article
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Biological communities exhibit multiple distribution patterns at metacommunity scale and assessing the major drivers of these patterns is a key issue in community ecology. Here we aimed to investigate how the environmental and geographic gradients shape the distribution patterns of macrophytes at metacommunity level. We applied the framework of the elements of metacommunity structure (EMS) to identify the distinct types of 48 macrophyte metacommunities in the Hengduan Mountain Region (HDMR) of China. Then we used generalized linear model and model selection approaches to determine which variables contributed to the variations of EMS, and linear discriminant function analysis to evaluate how well the tested variables in predicting the metacommunity patterns. We found wide variations of the three EMS (i.e., coherence, range turnover, and range boundary clumping). Latitude and alpha diversity were most important in determining coherence, nestedness was mostly related to turnover, while sampling depth was significantly associated with boundary clumping. Seven metacommunity types were identified in HDMR and most metacommunities fitted best the Gleasonian and Clementsian patterns as well as their quasi-structures. Notably, Gleasonian and Q-Gleasonian patterns as well as the other three patterns (i.e., Q-nested, evenly spaced, and nested) were for the first time detected for macrophytes. These metacommunity types were best discriminated by nestedness, altitude, and latitude. Our results provide strong evidences of the impact of geographic patterns on macrophyte metacommunities, with the Gleasonian patterns being dominant at the two ends of latitude/altitude gradients and the Clementsian patterns being common in the middle of the gradients.
... hydrological and physico-chemical changes) can also be approached through a trait-based analysis (Culp et al., 2011). Species traits, i.e. measurable organisms features describing, for example, body size, fecundity, and ecological preferences (McGill et al., 2006), have demonstrated consistent responses to environmental and hydrological variation across taxonomic boundaries (Frimpong and Angermeier, 2010;Göthe et al., 2017) and provide a better mechanistic understanding of the community responses to natural and anthropogenic stressors (Statzner and Bêche, 2010;White et al., 2017). For instance, the dominance of different macroinvertebrate feeding groups (Larsen et al., 2021) or different fish life strategies (Oliveira et al., 2018) are reported to vary significantly in response to flow alteration. ...
Article
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Rivers and streams have suffered multiple transformations to attend the increasing water demands worldwide. Among these, dams and reservoirs cause some of the most severe ecological impacts on rivers, altering the river flow and thermal regimens, nutrient and sediment fluxes, and network connectivity. However, in the context of the different dam purposes and operational schemes, knowledge of the ecological impacts on the riverine biota is still limited. In this study, our main goal was to assess dam-related effects (e.g. hydrological and thermal alteration, water quality changes) on river biological communities and identify key ecological responses associated to flow regulation. To achieve this, diatom, macroinvertebrate, and fish communities were surveyed in control (n = 8) and impacted (n = 11) streams (i.e. downstream of irrigation or hydropower dams) along three consecutive years. The study design aimed at minimising the environmental variability among control and impacts using previously established hydrological classifications. This allowed focusing primarily on the effects of dam operation schemes. In addition to traditional biotic indices based on the composition and structure of these communities, we assessed community-level responses using trait-based analyses with multivariate and fourth-corner analyses. The ecological changes varied with dam purpose and, in general, favoured disturbance-tolerant traits. Common biotic indices did not consistently respond to dam uses; trait-based analyses, in contrast, provided a more detailed picture of the dam-related effects on the studied river communities, with macroinvertebrate traits showing the strongest correlations to dam-related hydrological and physico-chemical variables, followed by diatoms and fish. Changes in the biological communities downstream of irrigation dams were mostly related to the inversion of the seasonal flow regimes (e.g. increases in the summer flows and magnitude of low flow extremes; decreases in the winter flows and in the frequency and magnitude of extreme high flow events) and the reduction of nutrient concentration. These changes favoured planktonic diatoms, macroinvertebrates with short life cycles and small body sizes, and fish feeding on the water column. Hydropower dams elevated significantly the rate of flow change and water temperature, favouring low profile adnate diatoms, multivoltine and passively dispersed macroinvertebrates, and scrapers. The key relationships identified in our study are useful to underpin river biodiversity conservation strategies and to set future research directions aiming at reducing the negative effects of dam operation schemes.
... In addition, the manner in which species use resources (from water, air or sediment) and the possession of different biological and ecological traits or adaptations such as life forms (position in the water column) also determine macrophyte diversity patterns (Santamaría, 2002;Alahuhta & Heino, 2013). For example, direct connection to aerial carbon and oxygen, improved light availability and wind dispersal make emergent macrophytes more efficient competitors and dispersers than other macrophytes , whereas floating and submerged plants appear generally more sensitive to water quality than emergent species (Akasaka et al., 2010;Göthe et al., 2017). ...
Article
Questions Given the current multiplicity of threats to pond biodiversity, there is a clear need to examine which environmental drivers determine the composition and distribution of species. Using wetland plants as pond biodiversity surrogates, two questions led to this work: How do wetland plant species assemblages and abundance vary across local‐ and regional‐scale classification schemes in wetlands? How does wetland plant beta‐diversity vary within these wetland classification schemes? Location Western Patagonia, Argentina, from 36°S to 56°S and from 73°W to 65°W. Methods Wetland plant distribution constrained by water and climatic factors was analyzed using canonical correspondence analysis. Variance partitioning analysis was performed to assess which classification scheme (phytogeographical units, wetland regions, wetland genesis and hydrogeomorphological types) better explained variation in plant composition. An IndVal analysis was also carried out to detect taxa with the highest association values (indicator taxa) for the different categories of wetland classification. Beta‐diversity was calculated to evaluate variation patterns within classification schemes. Results Plant distribution was mainly related to site location across the latitudinal gradient, following a decreasing pattern of air temperature from northern to southern wetlands. Variance partitioning analysis confirmed the effectiveness of a regional‐scale classification (wetland regions) in predicting plant associations, and the IndVal analysis also highlighted this classification scheme above the remainder, sustaining the highest number of indicator taxa. Wetland plant beta‐diversity patterns were explained by relatively high species turnover, with species composition showing low nestedness values. Conclusion Climate factors rather than local characteristics were the main drivers of plant distribution at the wide regional scale analyzed. Wetland region (classification based on climatic criteria) was the most effective scheme in predicting plant associations and sustaining the highest number of indicator taxa. Also, ponds located in the Patagonian Andes and those with a glacigenic origin contribute most to the regional wetland plant diversity. Therefore, these aspects should be taken directly into account in the future delineation of protected areas to increase the resilience of Patagonian wetland habitats and their associated biota, and to maintain the ecosystem services that they provide.
... These functional trait groups are associated with light interception, plant architecture, organ turnover and use of niche space in canopy (Willby et al., 2000). They are important functional features of aquatic macrophytes (Göthe et al., 2017), including those inhabiting boreal lakes . We followed Toivonen and Huttunen (1995) and Schmidt-Kloiber and Hering (2015) We also selected three functional trait groups for macroinvertebrates, including functional feeding habits (i.e., scrapers, gatherers, filterers, shredders and predators), substratum associations (i.e., burrowers, crawlers, sprawlers, sessiles, semi-sessile and swimmers) and body size (i.e., dry mass). ...
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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.
... The incorporation of Moran's Eigenvectors of spatial relationship in the redundancy analysis increased model performance significantly. The impact of both environmental and spatial factors in macrophyte species compositions is also reported by in Minnesota, USA, Göthe et al. (2017) in Denmark. Also, Grimaldo et al. (2016) reported that a substantial proportion of variations of community composition and species diversity of macrophytes was accounted for by environmental variables and their spatial interactions across the temperate and tropical calcareous forest. ...
Article
Spatial patterns of aquatic species are indicative of the quality of the in-stream water quality as well as that of the surrounding watershed. The relationships among aquatic species diversity, water quality, and watershed characteristics are not well explored in the Himalayan watershed. In this work, we analyzed the impacts of in-stream water quality, watershed socio-environmental conditions, and spatial predictors on the species composition of aquatic plants and macroinvertebrates. We collected macrophytes, phytoplankton, and macro-invertebrate samples and measured with dissolved oxygen and electrical conductivity of the lakes and rivers of the Setikhola watershed, Central Nepal. The watershed landscape variables such as landcover types, population density, and topography along with spatial factors derived from the spatial connectivity matrices were used as explanatory variables to explore species composition using redundancy analysis. We reported 39 macrophyte species, 105 phytoplankton species, and 35 families of macroinvertebrates. The macrophyte species belonging to the family Potamogetonaceae were dominant, as were the phytoplankton species belonging to Bacillariophyceae; most macro-invertebrates belonged to families in the order Diptera. We report a significant impact on watershed human population density as well as the electrical conductivity of the water on aquatic species composition. Inclusion of spatial factors increased model predictive performance of macrophyte and phytoplankton species composition. This study can help in a robust understanding of aquatic systems in relation to corresponding socio-environmental settings to manage them with optimal benefits for the ecosystems and people.
... Our study showed that environmental factors were more important than spatial factors in affecting the three facets of diversity indices, and the key environmental factors were related to the eutrophication status of lakes (e.g., aquatic vegetation cover, Chl a and nutrient concentrations). The predominant role of environmental filtering over spatial effects in shaping a metacommunity of benthic macroinvertebrate assemblages have frequently been reported in macroinvertebrate studies in other regions (e.g., Göthe et al., 2017;Heino and Tolonen, 2017a;Jiang et al., 2021b). Several recent studies done in the Yangtze River floodplain have also highlighted the deterministic role of water quality variables (e.g., nutrients) in affecting macroinvertebrate assemblages (Jiang et al., 2013;Pan et al., 2015;Zhang et al., 2019b). ...
Article
The accelerated eutrophication of freshwater lakes has become an environmental problem worldwide. Increasing numbers of studies highlight the need to incorporate functional and phylogenetic information of species into bioassessment programms, but it is still poorly understood how eutrophication affects multiple diversity facets of freshwater communities. Here, we assessed the responses of taxonomic, phylogenetic and functional diversity of benthic macroinvertebrates to water eutrophication in 33 lakes in the Yangtze River floodplain in China. Our results showed that macroinvertebrate assemblage structure was significantly different among four lake groups (river-connected, macrophyte-dominated, macrophyte-algae transition, and algae-dominated). Three taxonomic, two phylogenetic and two functional diversity indices were significantly different among the lake groups. Except for the increasing trend of Lambda⁺, these metrics showed a clear decreasing trend with increasing levels of eutrophication, with highest values detected in river-connected and macrophyte-dominated lakes, followed by macrophyte-algae transition lakes and algal-dominated lakes. Although differing in the number and identity of key environmental and spatial variables among the explanatory models of different diversity indices, environmental factors (eutrophication-related water quality variables) played more important role than spatial factors in structuring all three facets of alpha diversity. The predominant role of environmental filtering can be attributed to the strong eutrophication gradient across the studied lakes. Among the three diversity facets, functional diversity indices performed best in portraying anthropogenic disturbances, with variations in these indices being solely explained by environmental factors. Spatial factors were mostly weak or negligible in accounting for the variation in functional diversity indices, implying that trait-based indices are robust in portraying anthropogenic eutrophication in floodplain lakes. However, variation in some taxonomic and phylogenetic diversity indices were also affected by spatial factors, indicating that conservation practitioners and environmental managers should use these metrics with caution when providing solutions for addressing eutrophication in floodplain lakes.
... In particular, the functional trait value of the dominant species was found to drive ecosystem function [40,41], which was consistent with the present study. In addition, some studies have suggested that FD may be better in evaluating the response of communities to environmental changes and in predicting ecosystem functional changes [42,43]. The inconsistent results in regard to the relationship between diversity and the ecosystem function of different community types may be due to the differences in methods used [44]. ...
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To compare the relative importance of the biomass ratio hypothesis and the niche complementarity hypothesis in explaining changes in soil respiration (Rs), and to explore whether the relationship between biodiversity and Rs was affected by both biotic and abiotic factors, dynamic plant community monitoring was conducted in the Ebinur Lake Wetland Nature Reserve. By calculating the functional diversity (FD), community-weighted mean functional traits (CWM), and soil factors, the correlation between FD and Rs was compared using a linear regression model and a structural equation model. The results showed that (1) the CWM traits could better explain the changes of Rs than the FD, indicating that the biomass ratio hypothesis was more suitable for explaining changes in Rs in arid desert areas; and (2) the correlation between biodiversity and Rs was affected by the interaction between biological factors and environmental factors. Soil water content and species richness also affected Rs. Research on the relationship between biodiversity and Rs should examine both biotic and abiotic factors and clarify and explore various factors affecting Rs, which is of great significance to evaluate the community dynamics and variation characteristics of Rs. The study of various factors affecting Rs in this region is helpful to elucidate the process of the soil carbon cycle in arid desert areas.
... These results further highlight the roles of water chemistry in altering community composition through habitat filtration of bacteria adapted to specific water qualities. Not surprisingly, there were still parts of the variance that could not be explained in the study, similar to the results of the previous studies (Göthe et al., 2017;Schmera et al., 2018;Marmen et al., 2020). Lotic ecosystems have high spatial and temporal variability (Poff et al., 1997), and the stochasticity of abiotic and biotic factors within a watershed may produce considerable community variation (Townsend, 1989). ...
Article
The aim of this study was to examine the relationships between land use and bacterioplankton communities at different spatial scales and the mechanisms underlying the effects of land use on bacterioplankton communities. Here, surface water samples were collected in 14 tributaries of the Yuanhe River in August 2019 (wet season) and January 2020 (dry season), and high-throughput sequencing technology was used to determine the characteristics of the bacterioplankton communities. Statistical methods such as Bioenv and variance partitioning analysis (VPA) were used to explore the relationships among landscape structure (i.e., landscape compositions and landscape configurations), water chemistry, and bacterioplankton communities. Furthermore, metacommunity theory was employed to explain the mechanisms by which land use and water chemistry affect bacterial communities. The results showed that:① in general, the effects of landscape configuration on bacterial communities were weak, whereas the effects of landscape composition on bacterial communities were significant and greater at the buffer scale than that at the sub-basin scale. ② There was no distinct distance-decay pattern for the effects of landscape composition on bacterial communities from the near-distance (100 m) to the long-distance (1000 m) buffer zones, with the maximal effects occurring in the 500 m circular buffer (wet season) and 300 m riparian buffer (dry season), respectively. ③ Land use influenced the bacterioplankton communities both directly through exogenous inputs (i.e., "mass effect" process) and indirectly by affecting water chemistry (i.e., "species sorting" process). VPA showed that the total explanation of bacterial community variations by water chemistry and the intersection of water chemistry and land use (13.5% in the wet season and 11.7% in the dry season) was higher than that of land use alone (2.7% in the wet season and 6.9% in the dry season). These results suggest that mass effects and species sorting jointly shaped bacterial community assembly but that the effects of species sorting outweighed those of mass effects. This study revealed the variability of landscape structure at different spatial scales on bacterial communities, and its results will help to determine the optimal spatial scale affecting bacterial communities and provide a reference basis for watershed land-use management.
... Our study showed that environmental factors were more important than spatial factors in affecting the three facets of diversity indices, and the key environmental factors were related to the eutrophication status of lakes (e.g., aquatic vegetation cover, Chl a and nutrient concentrations). The predominant role of environmental filtering over spatial effects in shaping a metacommunity of benthic macroinvertebrate assemblages have frequently been reported in macroinvertebrate studies in other regions (e.g., Göthe et al., 2017;Heino and Tolonen, 2017a;Jiang et al., 2021b). Several recent studies done in the Yangtze River floodplain have also highlighted the deterministic role of water quality variables (e.g., nutrients) in affecting macroinvertebrate assemblages (Jiang et al., 2013;Pan et al., 2015;Zhang et al., 2019b). ...
... Conversely, plants in lower stress 100 environments tend to be taller with longer life cycles (Kyle and Leishman, 2009;Stromberg and Merritt, 2016;Mccoy-Sulentic et al., 2017). Factors such as nutrient loading Lukacs et al., 2019), light conditions (Baattrup-Pedersen et al., 2015), carbon availability (Lukacs et al., 2019), and anthropogenic interference (Baattrup-Pedersen et al., 2002;O'briain et al., 2017) are all key controllers of trait composition, with the environmental conditions better related to trait, rather than species, composition (Göthe et al., 2017). Furthermore, individual species have been shown to demonstrate differing traits 105 depending on external stresses. ...
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Vegetation plays a critical role in the modulation of fluvial process and morphological evolution. However, adequately capturing the spatial variability and complexity of vegetation characteristics remains a challenge. Currently, most of the research seeking to address these issues takes place at either the individual plant scale or via larger scale bulk classifications, with the former seeking to characterise vegetation-flow interactions and the latter identifying spatial variation in vegetation types. Herein, we devise a method which extracts functional vegetation traits using UAV laser scanning and multispectral imagery, and upscale these to reach scale guild classifications. Simultaneous monitoring of morphological change is undertaken to identify eco-geomorphic links between different guilds and the geomorphic response of the system in the context of long-term decadal changes. Identification of four guilds from quantitative structural modelling based on analysis of terrestrial and UAV based laser scanning and two further guilds from image analysis was achieved. These were upscaled to reach-scale guild classifications with an overall accuracy of 80 % and links to magnitudes of geomorphic activity explored. We show that different vegetation guilds have a role in influencing morphological change through the stabilisation of banks, but that limits on this influence are evident in the prior long-term analysis. This research reveals that remote sensing offers a solution to the difficulty of scaling traits-based approaches for eco-geomorphic research, and that these methods may be applied to larger areas using airborne laser scanning and satellite imagery datasets.
... These results further highlight the roles of water chemistry in altering community composition through habitat filtration of bacteria adapted to specific water qualities. Not surprisingly, there were still parts of the variance that could not be explained in the study, similar to the results of the previous studies (Göthe et al., 2017;Schmera et al., 2018;Marmen et al., 2020). Lotic ecosystems have high spatial and temporal variability (Poff et al., 1997), and the stochasticity of abiotic and biotic factors within a watershed may produce considerable community variation (Townsend, 1989). ...
Article
Bacterioplankton communities in rivers are strongly influenced by the surrounding landscape, yet the relationships between land use and bacterioplankton communities at multi-spatial scales and the mechanisms that shape bacterioplankton communities remain unclear. Here, we collected surface water samples from 14 tributaries of the Yuan River, a secondary tributary of the Yangtze River, which has been heavily impacted by human activities. We characterized the bacterioplankton communities by high-throughput sequencing techniques, and managed to identify the mechanisms governing bacterioplankton community assembly. The results showed that, in general, both landscape compositions and landscape configurations had significant effects on bacterial communities, and the effects were greater at the buffer scale than at the sub-basin scale. Additionally, there was no distinct distance-decay pattern for the effects of landscape structures on bacterial communities from the near-distance (100 m) to the long-distance (1000 m) buffer zones, with the maximal effects occurring in the 1000 m circular buffer (wet season) and 500 m riparian buffer (dry season) zone, respectively. Land use influenced the bacterioplankton community both directly through exogenous inputs (mass effect) and indirectly by affecting water chemistry (species sorting). Variance partitioning analyses showed that the total explanations of bacterial community variations by water chemistry and the intersections of water chemistry and land use (56.2% in wet season and 50.4% in dry season) were higher than that of land use alone (6.1% in wet season and 25.4% in dry season). These suggest that mass effects and species sorting jointly shaped bacterial community assembly, but that the effects of species sorting outweighed those of mass effects. Nevertheless, more biotic and abiotic factors need to be considered to better understand the microbial assembly mechanisms in anthropogenically influenced riverine ecosystems.
... for FD and functional redundancy of macroinvertebrate communities, which can indirectly affect ecosystem processes (Rasmussen et al., 2012;Voß & Schäfer, 2017). Therefore, community characterisations based on trait composition and functional diversity should enable a more rigorous assessment of communities to local ecological drivers (Heino et al., 2007;Göthe et al., 2017). Thus, to better understand the mechanisms structuring macroinvertebrate community responses to agricultural pollution, it is crucial to analyse the trait-environment interaction and the functional diversity of communities. ...
Thesis
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Agricultural land-use is a leading cause of water quality deterioration, biodiversity loss and impairment of stream functionality. Understanding the mechanisms by which agricultural land-use impair stream ecosystems is important for their effective management, especially in Africa. In this study, a combination of analytical tools, including macroinvertebrate taxonomic- and trait-based community analysis, functional indices, functional feeding groups and stable isotopes were used to investigate the effects of an increasing gradient of agricultural disturbance on the community composition, functional diversity, and food web of aquatic macroinvertebrates in the Kat River. Eight sites grouped into four site categories that represent a decreasing gradient of agricultural pollution (LUC 1< LUC 2 < LUC 3 and LUC 4) were selected. Macroinvertebrates and physiochemical variables and aquatic and terrestrial basal food sources were sampled from the eight sites over four sampling occasions; dry (winter and spring) and wet (summer and autumn) periods using the SASS 5 protocols. The taxonomy-based analysis showed different responses of macroinvertebrates to agricultural disturbance, with taxa such as Lymnaea spp., L. columella, Appasus spp. Biomphalaria spp., Trithemis spp. and Oligochaeta identified as potentially tolerant indicators of agricultural pollution. These taxa were positively correlated with the highly disturbed LUC 1 sites, and increasing levels of NH4-N, NO2-N, temperature and TDS. Conversely, Caenis spp., Afroptilum spp., Pseudocloeon piscis, Pseudocloeon spp., Baeti harrisoni, and Potamonautes spp. were sensitive to agricultural pollution, indicating strong negative associations with LUC 1 sites and NH4-N, NO2-N, salinity, temperature and TDS. Further, a multimetric index (MMI) was developed, validated and applied to assess agricultural disturbance in the Kat catchment. Of the 29 metrics that satisfactorily discriminated the LUC 4 site from the LUC 1, 2 and 3 sites, only eight metrics were non-redundant and integrated into Kat River MMI. The metrics integrated into the final MMI were Decapoda abundance, EPT/Chironomidae abundance, %EPT abundance, %Ephemeroptera abundance, %Caenidae abundance, %Hydropsychidae abundance, %Oligochaeta+chironomidae abundance and Shannon index. The developed MMI proved effective as a biomonitoring tool for assessing the ecological health of agricultural pollution in the Kat River. The trait-based analysis showed that traits such as haemoglobin, spiracle, adult aquatic life stage, active swimming and predatory lifestyle were positively correlated with LUC 1 sites, and were deemed tolerant-trait indicators of agricultural pollution. Shredding, medium body size (>10–20 mm), crawling and a preference for macrophytes were negatively correlated with LUC 1 sites, and were deemed sensitive-trait indicators of agricultural pollution in the Kat River. Functional diversity responded predictably to agricultural pollution, as functional indices such as functional richness, significantly declining along disturbance gradient during the dry and wet periods. The functional feeding group results revealed that gatherers and scrapers dominated in the Kat River, and together represented 0.27–0.43 of the invertebrate composition. Shredders were the lowest represented in the Kat River, with a relative abundance of 0.18. The FFG results showed that filter-feeders and predators increased in abundance along increasing environmental stress gradient, whereas shredders’ abundance decreased along the environmental stress gradient. Analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to estimate the contributions of aquatic and terrestrial resources to consumers across the four LUC and periods. Carbon contributions, determined using mixing models (Stable Isotope Analysis in R), revealed that consumers assimilated mainly aquatic sources (filamentous algae, macrophytes and biofilms), and this assimilation increased as agricultural disturbance increased across the two seasons. Terrestrial-derived food sources did not show evident variations among the LUCs, but C4 grasses changed along an increasing gradient of agricultural pollution during the two seasons. Further, there was enriched 15N of consumers, especially scrapers, predators and filter-feeders, along the disturbance gradient, whereas that of shredders declined along an agricultural disturbance gradient. NH4-N was the variable that affected consumers δ15N values, indicating a significant positive correlation with δ15N values for the majority of the consumers, especially gatherers, shredders and scrapers. The results of the study highlight the strength of a complementary approach to biomonitoring agricultural pollution in riverine systems. For example, the taxonomic analysis indicated changes in community composition, and the trait-based approach provided insights into the key stressors associated with agricultural pollution as a cause of water quality deterioration. The study contributes significantly to our understanding of riverine ecology in South Africa and, in particular the Kat River, in the context of agricultural pollution, which remains one of the leading causes of pollution of riverine ecosystems.
... g. Finn and Poff, 2005;Heino et al., 2007Heino et al., , 2013Hoeinghaus et al., 2007;Göthe et al., 2017). Our results showed considerable differences Table 2 Results of the pairwise Procrustes rotation analyses between sampling methods for taxa composition, relative taxa abundance structure and relative trait abundance structure. ...
Article
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Recent developments in environmental DNA (eDNA) metabarcoding suggest that eDNA-based representation of ecological communities can be a promising tool in both fundamental ecological research and environmental assessment. However, it is less known, how eDNA performs in characterising ecological communities and community-environment relationships at the regional scale compared with traditional sampling methods. Here, we used electrofishing (EF), gillnetting (GN) and eDNA-based surveys to compare their congruency in characterising the taxonomic and trait-based structure of (oxbow) lake fish communities and their structuring mechanisms. eDNA proved to be more effective in detecting taxa in the total samples and by traits than EF and GN. Principal coordinate analysis and multiple factor analysis showed a moderate separation of communities according to sampling methods for the taxon and the trait-based structures, respectively, but eDNA samples were always located in intermediate position in the ordination plots. Procrustes analyses indicated significant among-method congruency in community structure. However, in general, eDNA-based community patterns always showed higher correlation with either the EF or the GN-based community patterns, than the two traditional methods to each other. Variance partitioning in redundancy analyses indicated large differences among the sampling methods in the importance of environmental and spatial variables in shaping metacommunity structure. These results thus suggest that the sampling method can largely influence the identified mechanisms which govern fish metacommunity organisation. Our results suggest, that eDNA metabarcoding can be the best universal method for understanding the taxonomic and trait-based organisation of lake fish metacommunities.
... For TePa and TeAc groups, the results supported our prediction that spatial processes showed a greater importance on structuring the metacommunity patterns of passive dispersers (i.e., TePa) than environmental control that were more important for active dispersers (i.e., TeAc) (Fig. 3). Such findings are also in agreement with a few previous studies examining the interaction between dispersal mode and the processes structuring macroinvertebrate metacommunities (e.g., Cauvy-Fraunié et al. 2015;Göthe et al. 2017;Heino 2013;Li et al. 2019). However, for AqPa, we found small (when using watercourse distance) or even null (using overland distance) spatial signal and large environmental control Table 2 Mean value ± SD of richness and densities of entire assemblages and the three dispersal mode groups (aquatic passive, terrestrial passive and terrestrial active) and relative abundance of the most common orders, families, or subfamilies within the three groups. ...
Article
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It is generally recognized that dispersal mode can affect the relative role of environmental and spatial factors in structuring biotic communities. Disentangling the effects of dispersal mode on metacommunity structuring is essential to understanding the mechanisms of community assembly. Despite high seasonal variation in assemblage structure and phenological features of lotic macroinvertebrates, few studies examined the seasonal changes in the relative contribution of environmental and spatial processes. Here, we used two-season (spring and autumn) investigation data to link dispersal mode with local environmental and spatial factors that regulate macroinvertebrate metacommunity in a Chinese high-mountain stream network. Our aims were (1) to disentangle the relative role of environmental and spatial processes on structuring macroinvertebrate with different dispersal ability (aquatic passive: AqPa, terrestrial passive: TePa, and terrestrial active: TeAc) and (2) to determine seasonal shifts in metacommunity structuring processes. We found that assemblages of TeAc (with highest dispersal capacity) in both seasons were influenced more by environmental filtering than spatial structuring, whereas assemblages of TePa were mainly determined by spatial processes. Unexpectedly, AqPa group showed low spatial control in both seasons, probably due to their underestimated dispersal capacity via animal vector. The relative role of environmental and spatial factors was broadly stable across two seasons for AqPa and TeAc groups, but the TePa showed seasonal differences in the relative role of spatial factors, because of their seasonally changing dispersal capacity. In summary, our study emphasizes the use of dispersal mode for understanding metacommunity structuring mechanisms.
... These environmental filters determine the structure of the local community (Keddy 1992). Habitat complexity is seen as a key driving factor that structures communities and is usually positively related to taxonomic alpha diversity (MacArthur and MacArthur 1961) and functional alpha diversity (Göthe et al. 2017;Richardson et al. 2017). In addition, the variation in habitat complexity between different locations may be responsible for inducing spatial changes in ecological communities and, consequently, increase the functional beta diversity (Braghin et al. 2018;Peláez and Pavanelli 2019). ...
Article
Aquatic macrophytes increase habitat complexity and influence the structure of fish communities. We investigated relations between macrophyte stand complexity and functional alpha and beta diversity of fish. We sampled fish and plants in 30 macrophyte stands with differences in density and diversity in the Paraná River floodplain. The functional alpha diversity, measured as functional richness index (FRic), was calculated for each macrophyte stand. The functional beta diversity was examined using pairwise Jaccard dissimilarity as well as its turnover and nestedness components. We also partitioned functional beta diversity into contributions of single sites to overall beta diversity (LCBD) aiming to assess its relationship to macrophyte stand characteristics. We then used beta regressions and generalized dissimilarity modeling (GDM) to examine diversity patterns. As we expected, the greatest FRic occurred in stands with intermediate macrophyte density and high macrophyte diversity. The functional beta diversity responded mainly to the variation in macrophyte density, but the turnover component increased slowly at the beginning of the gradient (low density) and, after a certain point, it started to increase more rapidly. The stands that contributed the most to the functional beta diversity (higher LCBD values) were those with low and high FRic and, consequently, with lower and higher macrophyte density, as well as lowest macrophyte diversity. Our findings highlight the role of macrophytes as environmental filters that select the traits in fish communities, and the variation in fish traits is probably a result of factors such as food availability, shelter from predators and physical space for locomotion.
... In this investigation, our goal was to examine how individual taxa, thermal guilds (cold-water vs. warm-water) and communities of stream diatoms, insects and fish might respond to environmental gradients and climate change in the conterminous USA. Given that local and watershed factors have been shown to be important determinants of the distributions of freshwater taxa in community-level analyses (Göthe et al., 2017;Li et al., 2012;Potapova & Charles, 2002, 2003, our first objective was to examine the strength by which taxa within each group were modelled by water chemistry, watershed, climate and all their combinations. Our second objective was to analyse how species probabilities of occurrence and distributional shifts vary across future climate change scenarios in 2050 and 2070. ...
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Aim Biodiversity on Earth is threatened by climate change. Despite the vulnerability of freshwater habitats to human impacts, most climate change projections have focused on terrestrial systems. Here, we examined how current distributions and biodiversity of stream taxa may change under mitigated, stabilizing, and increasing greenhouse gas emissions. Location Conterminous United States. Time period Present day to 2070. Major taxa studied Stream diatoms, insects, and fish. Methods We developed species distribution models for 336 freshwater taxa from 1227 distinct stream localities using water chemistry, watershed, and climatic variables. Models based on climate only were used to project changes in cold- versus warm-water taxa distributions and biodiversity under representative concentration pathways (RCPs) ranging from 2.6 W/m2 to 8.5 W/m2. Results In all three organismal groups, climate emerged as the strongest predictor of species distributions, providing comparable explanatory power to water chemistry and watershed variables combined. RCP-based projections suggested a widespread expansion of warm-water taxa out-pacing the decline of cold-water taxa. Consequently, overall species richness would increase, but beta diversity would decrease drastically with climate change severity. A closer look at individual taxa and functional guilds revealed that vulnerable cold-water taxa included i) diatom guilds forming the base and bulk of the biofilm, ii) environmentally sensitive insects, characteristic of unimpacted streams, and iii) ecologically and recreationally important salmonids, which were forecasted to diminish dramatically in source habitats. Warm-water fish projected to increase their distributions include bait bucket release minnows and dominant predators. Main conclusions Our results suggest potentially devastating climate change impacts to stream ecosystems, with restructuring of diatom, insect, and fish communities, diminished distributions of functionally important taxa, and widespread expansion of warm-water taxa, giving rise to biotic homogenization. As the magnitude of these biotic shifts depends on climate change severity, appropriate current policy decisions are necessary to preserve freshwater ecosystems.
... Tonkin et al. (2016) offered a similar explanation for higher turnover between locations for the riparian carabid beetle community. Additionally, spatial control of community composition is often species-specific (Göthe et al., 2017). Soininen et al. (2018) observed that in most cases, both total beta diversity and its replacement component decreased with decreasing dispersal abilities of taxa. ...
Article
Rock pool metacommunities are shaped by the dispersal ability of organisms, which together with environmental heterogeneity, determine whether the metacommu-nity is structured more by environmental or spatial factors. To understand the effect of interspecific differences in dispersal capacity on beta diversity patterns and metacommunity structure, we studied aquatic Heteroptera (an actively dispersing insect group with species exhibiting flight polymorphism) in the rock pools on three outcrops in the Western Ghats, India. We used an abundance-based gamma diversity partitioning framework to assess the percent contributions of similarity (S) and the decompositions of beta diversity-abundance difference (D) and abundance replacement (R) to community structure for two mobility groups, that is, flying and flightless species. We compared the variation in beta diversity components "D" and "R" within and between outcrops for both mobility groups. We also studied the effects of the local environment on both mobility groups using redundancy analysis. Percent contributions of "S", "D" and "R" changed according to the mobility group, with higher nestedness (S+D) in flying species (74.2%) and higher beta diversity (R+D) in flightless species (76.3%). There was a significant variation in overall beta diversity between outcrops for the respective mobility groups, caused by abundance difference for flying species (p = .003) and by abundance replacement for flightless species (p = .003). Flying and flightless species were not associated with different environmental variables. Our study demonstrates that dispersal capacity is responsible for structuring regional diversity, with distinct sources of dissimilarity being associated with each mobility group: Abundance replacements between assemblages imposed by dispersal limitation for flightless species and abundance differences in assemblages of flying species, which might reflect the carrying capacity of the habitats.
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Chapter
The assemblage of species found at a location derives from the regional pool of species, governed by the ability of each species to colonize new habitat, and the matching of individual species to available resources, habitat, and one another. Regional species richness displays intriguing geographical patterns, best described for freshwater fishes. The number of species is inversely related to latitude, increases with drainage area and discharge of the river system, and differs among regions at the same latitude in both number of species and the traits of species present. System productivity, habitat diversity, and historical events are amongst the explanations for these patterns. At local scales, the number and relative abundance of species, their traits and functional roles, and energy pathways through food webs are useful descriptors of community structure. The processes that influence the assembly and maintenance of local communities include niche-based models that focus on the interplay between biotic interactions and abiotic forces, the habitat template model based on the association of individual species with habitat features, and disturbance models that emphasize the interplay between species interactions and variation in environmental factors that periodically reduce the abundance of some or all species in the community.
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Spatial synchrony in population dynamics has been identified in most taxonomic groups. Numerous studies have reported varying levels of spatial synchrony among closely-related species, suggesting that species’ characteristics may play a role in determining the level of synchrony. However, few studies have attempted to relate this synchrony to the ecological characteristics and/or life-history traits of species. Yet, as to some extent the extinction risk may be related to synchrony patterns, identifying a link between species’ characteristics and spatial synchrony is crucial, and would help us to define effective conservation planning. Here, we investigated whether species attributes and temperature synchrony (i.e. a proxy of the Moran effect) account for the differences in spatial population synchrony observed in 27 stream fish species in France. After measuring and testing the level of synchrony for each species, we performed a comparative analysis to detect the phylogenetic signal of these levels, and to construct various multi-predictor models with species traits and temperature synchrony as covariates, while taking phylogenetic relatedness into account. We then performed model averaging on selected models to take model uncertainty into account in our parameter estimates. Fifteen of the 27 species displayed a significant level of synchrony. Synchrony was weak, but highly variable between species, and was not conserved across the phylogeny. We found that some species’ characteristics significantly influenced synchrony levels. Indeed, the average model indicated that species associated with greater dispersal abilities, lower thermal tolerance, and opportunistic strategy displayed a higher degree of synchrony. These findings indicate that phylogeny and spatial temperature synchrony do not provide information pertinent for explaining the variations in species’ synchrony levels, whereas the dispersal abilities, the life-history strategies and the upper thermal tolerance limits of species do appear to be quite reliable predictors of synchrony levels.
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Regional and local processes are thought to influence community phylogenetic and species diversity, but have proved challenging to distinguish. We disentangled the effects of local (limiting similarity and habitat filtering) and regional processes (biogeography, history and geographical constraints) on the species and phylogenetic diversity of native riverine fish communities across France. Fish species richness ( SR ), phylogenetic diversity (estimated as the phylogenetic species variability metric, PSV ) and trait evenness (estimated from 17 ecological and life‐history traits) were estimated for fish at 932 sampling sites across 42 river basins in France. A phylogenetic signal in traits and species responses to environment variation were estimated using linear models. Null models were developed to test whether river basins constrain the PSV of the communities. Hierarchical linear models were fitted to PSV and SR to partition the variance explained by local and regional processes. Fish species richness and phylogenetic diversity were negatively correlated across sites ( r = −0.589, P < 0 001). There was a phylogenetic signal in species traits, but only a weak signal in species responses to environmental variation across sites. The null models suggested that river basins constrain community PSV . Local‐scale predictors (temperature, landscape position and trait evenness) explained the variation in both PSV and SR , while regional‐scale predictors (latitude, longitude and basin surface area) explained the variation only in SR . Significant interaction terms between local‐ and regional‐scale predictors were also detected for both metrics. Local‐scale processes, habitat filtering and limiting similarity, probably determine the species composition of fish communities across France, while broad‐scale, regional processes constrain community composition both directly and indirectly by affecting the strength of these local‐scale processes. By analysing phylogenetic diversity and species richness simultaneously, a full picture of the drivers of local‐scale diversity can be determined.
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There is a long tradition of river monitoring using taxonomy-based metrics to assess environmental quality in Europe via benthic macroinvertebrate communities. A promising alternative is the use of their species life-history traits. Both methods (taxonomy-based and trait-based), however, have relied on the time-consuming identification of taxa. River biotopes, (i.e. 1–100 m2 ‘habitats’ with associated species assemblages), have long been seen as a useful and meaningful way of linking the ecology of macroinvertebrates and river hydro-morphology and can be used to assess hydro-morphological degradation in rivers. However, between-river taxonomic differences, especially at large spatial scale, had prevented a general test of this concept until now. The species trait approach may overcome this obstacle across broad geographical areas, using biotopes as the hydro-morphological units which have characteristic species trait assemblages. We collected macroinvertebrate data from discrete 512 patches, comprising 13 river biotopes, from seven rivers in England and Wales. The aim was to test whether river biotopes were better predictors of macroinvertebrate trait profiles than taxonomic composition (genera, families, orders) in rivers, independently of the phylogenetic effects and catchment scale characteristics (i.e. hydrology, geography and land cover). We also tested whether species richness and diversity were better related to biotopes than to rivers. River biotopes explained 40% of the variance in macroinvertebrate trait profiles across the rivers, largely independently of catchment characteristics. There was a strong phylogenetic signature, however. River biotopes were better at predicting macroinvertebrate trait profiles than taxonomic composition across rivers, whatever the taxonomic resolution. River biotopes were better than river identity at explaining the variability in taxonomic richness and diversity (40% and ≤10%, respectively). Detailed trait-biotope associations agreed with independent a priori predictions relating trait categories to near river bed flows. Hence, species traits provided a much needed mechanistic understanding and predictive ability across a broad geographical area. We show that integration of the multiple biological trait approach with river biotopes at the interface between ecology and hydro-morphology provides a wealth of new information and potential applications for river science and management.
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Wetland habitats are among the most threatened of all ecosystems today and still face an on-going threat despite several international agreements and national policies. In Europe, the Habitats Directive (HD) plays an important role in the protection of habitats and species of European importance. In the present study we use statistical modelling techniques and geographic information systems to explore linkages between HD Annex 1 listed habitats in wetlands and catchment characteristics, e.g. size, geology and land uses at various spatial scales (50 m, 100 m, 500 m and whole catchment). Specifically we test if we can predict the spatial distribution of protected wetland habitats from catchment characteristics and additionally that we can identify critical variables and their spatial scale. We find that we are able to use catchment characteristics to predict the occurrence of protected habitats in riparian areas with 76% correctly classified habitats. At the catchment scale a low percentage of anthropogenic drainage together with a high percentage of forest increase the probability of having protected habitats in riparian areas, whereas at the local scale a low percentage of arable land and a high percentage of natural vegetation increase the probability of having protected habitats. We believe that the model approach used can have important implications. Firstly, the model can be used as a screening tool for identifying areas with potential conservation value. Secondly, the model can also be used as a management planning tool. Riparian areas are increasingly being used as mitigation measures to reduce loads of nutrients and toxic compounds to freshwater ecosystems. These measures may interfere with the hydrological and biochemical settings in riparian areas and threaten communities that are sensitive to eutrophication, e.g. HD Annex 1 habitats. The model can with a relatively high predictability point to areas where mitigation measures should be avoided because of conservation interests. Similarly the model can be used to identify areas that potentially can be restored successfully.
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Acidity is well known to influence stream biota, but the less well-studied spatial and temporal distributions of acidity are likely to play a larger ecological role than average values. We present data on spatial variability of chemical parameters contributing to acidity during winter baseflow and spring flood periods in Krycklan, a fourth-order boreal stream network in northern Sweden. Fifteen stream sites were monitored in subcatchments spanning 3 orders of magnitude in size and representing a wide range of percent wetland. At baseflow, pH ranged from 3.9 to 6.5 at the different sites. Baseflow dissolved organic carbon (DOC) concentration varied by an order of magnitude and was positively correlated with subcatchment percent wetland, resulting in high spatial variability in dissociated organic acids (OA-). During spring flood, DOC and OA- increased in forested sites and decreased in wetland sites, resulting in reduced spatial variability in their concentrations. In contrast, base cations and strong acid anions diluted throughout the stream network, resulting in decreased acid neutralizing capacity (ANC) at all sites. The spatial variability of base cations increased slightly with high flow. As a result of the changes in OA- and ANC, pH dropped at all but the most acidic site, giving a slightly narrowed pH range during spring flood (4.2-6.1). The transition from winter to spring flood stream chemistry could largely be explained by: (1) a shift from mineral to upper riparian organic soil flow paths in forested catchments and (2) dilution of peat water with snowmelt in wetland catchments.
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Effective catchment management in the face of landuse alteration depends on our ability to quantify ecologically significant changes and to discriminate among varying levels of impact. We compared the efficiency of traditional structural indices of change (species composition) with functional measures based on species traits (including life-history, trophic, and morphological features) in an analysis of grassland streams along a gradient of agricultural development (ungrazed native tussock, grazed tussock, extensively grazed pasture, and intensive dairy and deer farming). Streams were categorized in relation to overall agricultural intensity, and separately in terms of increasing nutrient concentrations and fine sediments on the streambed. Only 5 of 60 individual species demonstrated a significant separation across the landuse gradient, whereas 14 of 53 trait categories did so. Traits associated with population resilience (short generation time, asexual reproduction) became more prevalent with more intense agricultural pressure, reflecting predicted increases in intensity and frequency of stream disturbance. We observed a shift away from a tendency to lay unattached eggs at the water surface of the stream, reflecting the increasing likelihood of smothering by sediment, as well as increases in highly flexible and streamlined body shapes. Principal components and correspondence analyses involving species or trait composition all were able to discriminate landuse practises, but more of the overall between-landuse variance was accounted for by trait composition than species composition. All biological measures (species or trait composition) were correlated with both nutrient concentrations and sedimentation. Nutrient concentrations were better related to species and trait-category densities, whereas sedimentation was related to trait-category relative abundances. Overall, species traits successfully complemented traditional structural measures by helping to differentiate the consequences of landuse intensification in grassland stream communities. Rather than simply recording a loss or reduction of species, our functional approach was able to identify sensitive life-history characteristics linked to the functioning of ecosystems, thereby facilitating the development of targeted management actions.
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It is critical that the impacts of environmental stressors on natural systems are detected, monitored and assessed accurately in order to legislate effectively and to protect and restore ecosystems. Biomonitoring underpins much of modern resource management, especially in fresh waters, and has received significant sums of money and research effort during its development. Despite this, the incorporation of science has not been effective and the management tools developed are sometimes inappropriate and poorly designed. Much biomonitoring has developed largely in isolation from general ecological theory, despite the fact that many of its fundamental principles ultimately stem from basic concepts, such as niche theory, the habitat template and the r-K continuum. Consequently, biomonitoring has not kept pace with scientific advances, which has compromised its ability to deal with emerging environmental stressors such as climate change and habitat degradation. A reconnection with its ecological roots and the incorporation of robust statistical frameworks are key to progress and meeting future challenges.The vast amount of information already collected represents a potentially valuable, and largely untapped, resource that could be used more effectively in protecting ecosystems and in advancing general ecology. Biomonitoring programmes have often accumulated valuable long-term data series, which could be useful outside the scope of the original aims. However, it is timely to assess critically existing biomonitoring approaches to help ensure future programmes operate within a sound scientific framework and cost-effectively. Investing a small proportion of available budgets to review effectiveness would pay considerable dividends.Increasing activity has been stimulated by new legislation that carries the threat of penalties for non-compliance with environmental targets, as is proposed, for example, in the EU's Water Framework Directive. If biomonitoring produces poor-quality data and has a weak scientific basis, it may lead either to unjustified burdens placed on the users of water resources, or to undetected environmental damage. We present some examples of good practice and suggest new ways to strengthen the scientific rigour that underpins biomonitoring programmes, as well as highlighting potentially rewarding new approaches and technologies that could complement existing methods.
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Here we classify selected European hydrophytes into ‘attribute groups’ based on the possession of homogenous sets of characteristics, and explore the correspondence between these attribute groups, or individual attributes, and habitat use. Non‐hierarchical clustering was used to assign 120 species to twenty groups based on a matrix of categorical scores for literature‐ and field‐derived information covering seventeen intrinsic morphological and life‐history traits. Subdivision of some of these traits produced a total of 58 attributes (i.e. modalities). The robustness of this classification was confirmed by a high rate of reclassification (92%) under multiple discriminant analysis (MDA). The phylogenetic contribution was explored using ordination methods with taxonomy at family level acting as a covariable. Our approach differed from earlier classifications based on growth or life form because we regarded growth form plasticity as a property of the species and its range of growing conditions, rather than of each individual population, and we considered additional (e.g. regenerative) traits. However, some conventional life form groups were preserved (i.e. utricularids, isoetids, hydrocharids and lemnids). Some parallels existed with established theory on terrestrial plant growth strategies, but we used strictly intrinsic attributes relevant specifically to hydrophytes and our groups could not be decomposed into three or four primary strategies. Only finer levels of partitioning appear to be of fundamental and applied ecological relevance in hydrophytes. A principal components analysis ordination based on 26 attributes related to physical habitat utilization separated species and their attribute groups along axes relating to: (a) flow, substratum grade and organic matter content, scour frequency, and sedimentation; and (b) depth, water level stability and biotic disturbance. A MDA applied to species ordination scores indicated only a modest overall correspondence between attribute groups and habitat use (54% correct reclassification). Poor reclassification was the result of intergroup overlap (indicating alternative sets of attributes for a given habitat) or high intragroup variance in habitat utilization (indicating commonality of attributes between different habitats). These results are interpreted in terms of trade‐offs between resistance and resilience traits, ‘functional plasticity’ in traits, phylogenetic dependence in some groups and methodological constraints. The predictive potential of hydrophyte groups and their limitations are discussed. Redundancy analysis revealed a highly significant correlation between traits and habitat use ( P < 0.01). Our attribute matrix explained 72% of variation in physical habitat use with eight attributes (i.e. turions, anchored emergent leaves, high or low body flexibility, high root:shoot biomass ratio, free‐floating surface or free‐floating submerged growth form, and annual life history) explaining half of this variation. Most attributes were mapped in accordance with habitat template predictions, although tests were confounded by the underlying correlation between spatial and temporal heterogeneity. The main features were: (a) a trade‐off between resistance‐type traits (related to stream lining, flexibility and anchorage) in more spatially heterogenous riverine and littoral zone habitats, and resilience type traits (i.e. turions, very small body size and free‐floating growth forms) in spatially simple, rarely disturbed habitats, such as backwaters and canals; and (b) a shift from high investment competitive traits with a low reproductive output in deep stable habitats to classically ruderal and desiccation resistance traits in shallow fluctuating habitats.
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1. The fundamental importance of freshwater resources, the rapid extinction rate among freshwater species and the pronounced sensitivity of freshwater ecosystems to climate change together signal a pre-eminent need for renewed scientific focus and greater resources. Against this background, the Freshwater Biological Association in 2008 launched a new series of ‘summit’ Conferences in Aquatic Biology intended to develop and showcase the application of ecological science to major issues in freshwater management. 2. This collection of studies arose from the first summit entitled ‘Multiple Stressors in Freshwater Ecosystems’. Although freshwater science and management are replete with mutiple-stressor problems, few studies have been designed explicitly to untangle their effects. 3. The individual case studies that follow reveal the wide array of freshwaters affected by multiple stressors, the spatial and temporal scales involved, the species and ecosystem processes affected, the complex interactions between ecology and socioeconomics that engender such effects, the approaches advocated to address the problems and the challenges of restoring affected systems. The studies also illustrate the extent to which new challenges are emerging (e.g. through climate change), but also they develop a vision of how freshwaters might be managed sustainably to offset multiple stressors in future. 4. More generically, these case studies illustrate (i) how freshwaters might be at particular risk of multiple-stressor effects because of conflicts in water use, and because the hydrological cycle vectors stressor effects so effectively and so extensively; (ii) that dramatic, nonlinear, ‘ecological surprises’ sometimes emerge as multiple-stressor effects develop and (iii) that good ecology and good ecologists add considerable value to other freshwater disciplines in understanding multiple stressors and managing their effects.
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Aquatic plants contribute to maintaining key functions and related biodiversity in freshwater ecosystems, and to provide the needs of human societies. The way the ecological niches of macrophytes are determined by abiotic filters and biotic ones is considered. A simple, broadly applicable model of the distribution of growth forms according to abiotic filters is proposed. The consequence for the dynamics of plant communities and the main threats to macrophyte occurrence and diversity are discussed. Key concepts Macrophytes contribute to maintaining key functions and related biodiversity in freshwater ecosystems, and to provide the needs of human societies. Most aquatic species are phylogenetically descended from terrestrial plants that have later adapted to aquatic life. Water plants are usually poorly lignified, as water preserves plants from gravitational stress, and are characterized by the presence of aerenchyma, which increases oxygen flux from shoots to roots, and by a large leaf surface, together with a thin cuticle, which increase contact with water and carbon uptake. Macrophyte dispersal relies partly on water drift, and thus on seed buoyancy and on the ability of plants to break themselves up and regrow from broken dispersed fragments, and partly on endozoochory by animals (mainly birds). In freshwater ecosystems, the production, community composition and life‐history traits of macrophytes are governed by the availability of carbon, nitrogen and phosphorous. Water movements (waves, flow velocity) tend to select streamlined or prostrate growth forms, and contribute to the dispersal of seeds and vegetative propagules. Moderate disturbances (by floods or drawdowns) decrease biotic interactions in aquatic plant communities and as a consequence favour biodiversity and decrease successional rate. Free‐floating and tall species with floating leaves are the most competitive for light, and usually dominate macrophyte communities when nutrient levels in the water are sufficiently high. In the framework of global change, eutrophication of freshwaters, together with decreases in natural disturbance regimes in river floodplains, increases in groundwater abstraction and the increase of temperature may all contribute in decreasing macrophyte biodiversity by favouring competitive and invasive species, to the detriment of ruderal, stress‐tolerant poorly competitive ones.
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Metacommunity structure can be shaped by a variety of processes operating at different spatial scales. With increasing scale, the compositional variation among local communities (beta diversity) may reflect stronger environmental heterogeneity, but may also reflect reduced exchange of organisms between habitat patches. We analyzed the spatial architecture of a metacommunity of cladoceran zooplankton in temporary pools of High Andes wetlands, with the objective of explaining the spatial dependency of its structure. The spatial distribution of the pools is hierarchical and highly discontinuous: pools are clustered within small wetlands, which lay scattered over valleys that are separated from each other by mountain ridges. We studied a total of 59 pools, belonging to six different wetlands in four different valleys. We assessed pool environmental heterogeneity and sampled active communities and dormant propagule banks of cladoceran zooplankton. Environmental heterogeneity proved very high within wetlands and showed almost no increase with increasing spatial scale. Conversely, diversity partitioning analyses indicated an increase in beta diversity with spatial scale, especially among valleys. Variation partitioning on environmental data and spatial RDA models suggested environmental heterogeneity as the most important generator of beta diversity within wetlands. At the largest spatial scale, beta diversity manifested itself mainly as a differentiation of species occurrence patterns among valleys, which could not be entirely explained by environmental variables. Our study thus presents a case where environmental control seems to be the dominant metacommunity structuring process at the smallest spatial scale, whereas neutral processes and dispersal limitation are the most likely generators of beta diversity at the largest spatial scale.