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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 km2 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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... 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. ...
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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.
... 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
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. Conterminous United States. Freshwater macroinvertebrates. 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. 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. 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.
... Stream species are subjected to both strong environmental filtering and dispersal limitation processes towards the headwaters (Tonkin et al. 2018). Moreover, local habitat is a well-known driver of variation in species richness and abundance of stream organisms (Pease et al. 2011;Göthe et al. 2017;Jyrkänkallio-Mikkola et al. 2017). However, because streams are nested within a fluvial hierarchy, these local variables are shaped by large-scale variables, such as geology, climate and land cover (Frissell et al. 1986;Leal et al. 2016;Benone et al. 2017). ...
... This is much greater than found in most studies for stream fish previously (e.g. Wang et al. 2003;Hoeinghaus et al. 2007;Alford 2014;Terra et al. 2016;Göthe et al. 2017) and is possibly due to the inclusion of large-scale variables regarding biogeography and catchment features (Sály et al. 2011;Dagosta and Pinna 2017). The strong association of biogeography with taxonomic composition likely reflects the large spatial extent covered by our six river basins in the Amazon. ...
... This seems to be the case for the Amazon, where streams within and between river basins show high dissimilarity in fish species composition (Mendonça et al. 2005;Leal et al. 2018, but see Dagosta and Pinna 2017). The importance of space in structuring local communities has been observed for aquatic organisms, such as diatoms (Jyrkänkallio-Mikkola et al. 2017), macrophytes (Göthe et al. 2017), and fish (Shurin et al. 2009;Cilleros et al. 2016), increasing at larger spatial scales that encompass larger environmental gradients and increased levels of dispersal limitations (Heino et al. 2015). Contrary to our expectations, functional beta diversity was strongly correlated with biogeographical variables, with no association from pure local and catchment variables. ...
Article
Environmental filtering and dispersal limitation are essential processes affecting the variability of ecological communities. However, their relative contributions are highly debated and remain largely unknown in several systems, such as the hyperdiverse Amazon Basin. We determined the relative role of local, catchment, spatial, and biogeographical variables on the taxonomic and functional alpha and beta diversity of stream fish. We sampled 54 streams across six river basins in the Amazon. For each stream, we obtained 35 local habitat variables and 11 climate-catchment variables. Watercourse distances and basin identity were converted into spatial and biogeographical variables, respectively. We found that taxonomic alpha diversity responds both to spatial and local predictors, whereas its functional counterpart was mainly associated with local variables. Biogeography was the main factor structuring taxonomic and functional beta diversity, with a secondary contribution of catchment and local variables. Locally, substrate type and isolation determined the number and relative abundance of species and traits. The shared variation between biogeographical and environmental variables, especially altitude and slope, were strongly associated with beta diversity patterns, indicating a joint role of habitat filtering and dispersal limitation. Our results show the need to include both spatial and environmental variables in studies of stream communities at large spatial scales, as they are related to distinct processes that regulate community structure. We also encourage future studies to account for the responses of multiple facets of biodiversity to different drivers, as they provide essential and complementary information for community ecology and biogeography.
... Many investigations have indicated the importance of both stochastic and deterministic processes in explaining the spatial distributions of aquatic organisms in lotic, lentic and lentic-lotic systems, such as fish (López-Delgado et al., 2019), phytoplankton and zooplankton (Guo et al., 2019b;Qu et al., 2018;Zhao et al., 2017), stream benthic algae (Tang et al., 2013;Wu et al., 2014) and macroinvertebrates (Yamada et al., 2014). However, the existing studies are often limited to single organism groups, while comparative studies (across tropic levels) are still largely lacking (Göthe et al., 2017;Wang et al., 2020). ...
... On the other hand, larger organisms and in particular those that are restricted to disperse within the river channels (e.g. fish) are expected to be more dispersal limited and thus more constrained by stochastic process (Göthe et al., 2017;Shurin et al., 2009). In addition, the contribution of stochastic process (indicated by pure spatial effect) is scale dependent and increases with geographic distance. ...
... For example, at large scales, stochastic process often outperforms deterministic process (Heino et al., 2010;Tang et al., 2013;Wu et al., 2014), while at small scales deterministic process often predominates Wu et al., 2018). While more and more researchers have applied metacommunity theory to compare the relative roles of stochastic and deterministic processes in shaping aquatic communities (Göthe et al., 2017;Guo et al., 2019b;Qu et al., 2018;Wu et al., 2018;Yamada et al., 2014;Zhao et al., 2017), inclusion of geo-climatic factors such as aspect, slope, climatic factors, is still scarce, although few studies have indicated their importance in shaping the distribution of aquatic organisms (Benito et al., 2018;He et al., 2020). Furthermore, translating metacommunity theory, which acknowledges both local (i.e. ...
... This is because mainstreams usually locate in the central position of river networks, where dispersal is facilitated by a continuous flux of migrants via mass effects . However, only few studies have tested the NPH by directly comparing the relative role of environmental filtering and spatial process structuring metacommunities in different network positions (Göthe et al., 2017;Henriques-Silva et al., 2019;Schmera et al., 2017). Also, little is known about the applicability of the NPH in different seasons with distinct hydrological regime. ...
... In addition, physical factors (e.g., mean depth and benthic substrates) and riparian conditions (e.g., % urban land-use) were found to be key environmental factors for variation in community structure. These factors have been previously recorded as influential predictors for macroinvertebrate communities in this river (Li et al., 2019a;Xing et al., 2019), as well as for aquatic organisms in other river networks around the world (Göthe et al., 2017;Jahnig and Lorenz, 2008;Li et al., 2012). ...
... This result was reasonable because tributary streams (especially headwater streams) are always the most geographically isolated systems in a drainage basin, and that organisms' dispersal among tributaries is anticipated to be limited (Finn and Poff, 2011). One may expect a conspicuous effect of spatial structuring via dispersal limitation on tributary communities (Göthe et al., 2017). On the other hand, it can also be inferred that the dispersal rates of organisms in the mainstream sites under research were neither very high nor strongly limited, and thus most species can track environmental variation there. ...
... Interestingly, studies investigating the same organismal group and using similar analytical techniques have reached different conclusions concerning the impact of spatial and environmental variable groups (e.g. for macroinvertebrates 9,12 or for fishes 7,9 ). Therefore, the question arises whether general drivers of aquatic communities can be identified and whether they are applicable to different river systems. ...
... However, several other studies identified environmental conditions as key drivers of spatial community structure 41 , including that of diatoms 42 , macroinvertebrates 12,[43][44][45] , and fishes 12,43,46 . The addition of nematodes to these already very different organismal groups provides further evidence of the high connectivity of sites within river networks, independent of the dispersal mode (passive or active) and aquatic zone (benthic or pelagic). ...
... However, several other studies identified environmental conditions as key drivers of spatial community structure 41 , including that of diatoms 42 , macroinvertebrates 12,[43][44][45] , and fishes 12,43,46 . The addition of nematodes to these already very different organismal groups provides further evidence of the high connectivity of sites within river networks, independent of the dispersal mode (passive or active) and aquatic zone (benthic or pelagic). ...
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The field of metacommunity studies is growing rapidly, including recent applications to river networks. Most of these studies have targeted a single river network but whether their findings are relevant to other river systems is unknown. This study investigated the influence of environmental, spatial and temporal parameters on the community structure of nematodes in the river networks of the Elbe and Rhine. We asked whether the variance in community structure was better explained by spatial variables representing the watercourse than by overland distances. After determining the patterns in the Elbe river network, we tested whether they also explained the Rhine data. The Elbe data were evaluated using a boosted regression tree analysis. The predictive ability of the model was then assessed using the Rhine data. In addition to strong temporal dynamics, environmental factors were more important than spatial factors in structuring riverine nematode communities. Community structure was more strongly influenced by watercourse than by Euclidean distances. Application of the model’s predictions to the Rhine data correlated significantly with field observations. Our model shows that the consequences of changes in environmental factors or habitat connectivity for aquatic communities across different river networks are quantifiable.
... 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.
... 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). ...
... 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.
... 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.
... Particularly, β diversity can be considered a measure that compares species diversity using two other diversity indices (i.e., alpha and gamma diversity indices) (Baselga 2010). Therefore, β diversity has been regarded as a basic pattern in biogeography and macroecology (Gaston 2000), and it has been one of the central issues in metacommunity investigations in recent decades (Veech and Crist 2007;Tuomisto 2010a, b;Cañedo-Argüelles et al. 2015;Wen et al. 2016;Göthe et al. 2017). Based on β diversity, many studies have concentrated on the dissimilarity of species composition between sites (Jost et al. 2011;Cañedo-Argüelles et al. 2015;Tonkin et al. 2016;Wen et al. 2016;Dias et al. 2017) and the relationships among species turnover, environmental factors (e.g., flow regime, barriers, altitude and climate conditions) and geographic distance (e.g., Euclidean, network and flow) (Rouquette et al. 2013;Datry et al. 2016;Wen et al. 2016). ...
... This explanatory power is similar to the results of a study in Denmark (Göthe et al. 2017) but much lower than that measured in a mountain area in China (Dong et al. 2016;Wen et al. 2016). In high mountain streams, both LEnvDs and GeoDs were found to influence the structure of a metacommunity, with the latter contributing more than the former (Dong et al. 2016). ...
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Both environmental and geographic factors interact to structure the metacommunities in river networks, but the importance of these factors is difficult to distinguish. We used six aquatic taxonomic groups to test the relationship between environmental and geographic factors and their effect on species turnover patterns in an agriculturally dominated river (Chaohu Lake Basin, China). The relationships between three dissimilarity indices and geographic distance were assessed using the Mantel test while considering the differences in environmental factors between sites. Then, we employed a variation partitioning method to distinguish the isolated and combined effects of environmental and geographic distance on species turnover. There were significant relationships between environmental distance and species turnover in all groups. All organisms except periphytic diatoms were significantly correlated with two geographic (Euclidean and network) distances when the Chao dissimilarity index was considered. The results suggest that the strength of the correlations changed with environmental and geographic distances and with the aquatic community. The communities displayed more complex relationships with the distance measures when different dissimilarity (Jaccard, Chao, and Bray-Curtis dissimilarity) indices were considered. Nevertheless, aquatic communities are strongly influenced by both environmental and geographic distance, and the former has a stronger effect than the latter.
... Traditional taxonomic diversity indices treat species as equivalent units and assume that all species have the same responses to environmental impacts (Magurran, 2004), while functional diversity indices measure the diversity of functional traits, i.e., characteristics of organisms' phenotype that influence ecosystem functions and organisms' survival (Petchey and Gaston, 2006). Moreover, functional diversity may exhibit a relatively high correspondence with changes in environmental conditions, reflecting the resilience of ecosystems (Göthe et al., 2017;Menezes et al., 2015). ...
... Ecological Indicators 106 (2019) 105527 Functional attributes of assemblage composition have been widely used in stream bioassessments (Hering et al., 2004;Szocs et al., 2014;Tomanova et al., 2008), due to their ability to detect anthropogenic disturbances independently of taxonomic assemblages (Mondy and Usseglio-Polatera, 2014), although to a far lesser extent in lake bioassessment than in stream bioassessment. Most studies have focused on finding the relationship between trait states and environmental filters, and compared taxonomic approaches against functional approaches (Göthe et al., 2017;Zhang et al., 2019). Nevertheless, more attention should be paid to integrate biomonitoring protocols and functional approaches. ...
... To obtain functional dissimilarity of aquatic macrophytes, we used four biological traits: growth form, normal method of propagation, perennation and potential size. These are important biological traits of aquatic macrophytes (Willby et al. 2000, Göthe et al. 2017), affecting where the species can live, how they reproduce and what kind of life cycle they have. Growth form division consists of the following classes: ceratophyllid, elodeid, helophyte (incl. ...
... In such cases, the species obtained a value in between the ranked categories (i.e. 1.5 and 2.5), following Göthe et al. (2017). However, we weighted value 2, which indicates the presence of the attribute, at the expense of value 1, which indicates the occasional, but not general exhibition of the attribute. ...
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It has been predicted that spatial beta diversity shows a decreasing trend in the Anthropocene due to increasing human impact, causing biotic homogenisation. We aimed to discover if vascular aquatic macrophyte communities show different spatial patterns in beta diversity in relation to land use and environmental characteristics in different decades from 1940s to 2010s. We aimed to discover if spatial structures differ between species‐, phylogeny‐ and functional‐based beta diversity. We used presence–absence data of aquatic macrophytes from five decades from small boreal lakes. We utilized generalised dissimilarity modelling to analyse spatial patterns in beta diversity in relation to environmental gradients. We found that lake elevation and pH were the most important variables in each decade, while land use was not particularly important in shaping beta diversity patterns. We did not find signs of a decreasing trend in spatial beta diversity in our study area during the past 70 yr. We did not find signs of either biotic homogenisation or biotic differentiation (taxonomic, phylogenetic or functional). Vascular aquatic macrophyte communities showed only slightly different beta diversity patterns in relation to human impact across decades. The patterns of different facets of beta diversity diverged only slightly from each other. Lake position in the landscape, reflecting both natural connectivity and lake characteristics, explained the patterns found in beta diversity, probably because our study area has faced only modest changes in land use from 1940s to 2010s when compared globally. Our study highlights the fact that biotic homogenisation is not an unambiguous process acting similarly at all spatial and temporal scales or in different environments and different organism groups.
... Findings in metacommunity ecology, biogeography and conservation biology have highlighted that community composition and diversity are shaped by factors operating at multiple scales, involving local determinants, regional effects and historical factors (Göthe et al., 2017;Heino, 2011;Leibold and Chase, 2017). In line with such perspective and also our first hypothesis, our results showed that the four explanatory factor groups (i.e., local stressors, climatic factors, within-basin spatial factors and basin identity) all played important but different roles in determining variation in biodiversity indices. ...
... As expected, local stressors accounted for the highest proportion of variation in diversity indices, supporting the perspective that environmental filtering often preponderates over spatial processes in shaping metacommunities in aquatic ecosystems (Castilloescriva et al., 2017;Göthe et al., 2017;Nicacio and Juen, 2018). Generally, the relative variance contribution of environmental filtering (versus spatial factors) may be largely contingent on the lengths of environmental gradients, such as ranges in benthic habitat conditions and nutrient concentrations df degrees of freedom, SS square sum, MS mean sum, P (perm) P values using permutation of residuals under a reduced model. ...
Article
Metacommunity ecology emphasizes that community structure and diversity are not only determined by local environmental conditions through environmental filtering, but also by dispersal-related processes, such as mass effects, dispersal limitation and patch dynamics. However, the roles of dispersal processes are typically ignored in bioassessment approaches. Here, we simultaneously explored the potential influences of four groups of factors: local stressors, climatic factors, within-basin spatial factors and basin identity in explaining variation in diversity indices of macroinvertebrate assemblages from seven subtropical tributary rivers. A total of 12 biodiversity indices based on species identities, functional traits and taxonomic relatedness were calculated and used in the subsequent statistical analysis. Our results showed that, although differing in their relative importance, the four explanatory factor groups all played important roles in explaining variation in biodiversity indices. Of the pure fractions, index variation was best explained by local environmental stressors, whereas the other three explanatory factor groups appeared less influential. Furthermore, diversity indices from species, functional and taxonomic dimensions responded distinctly to the focal ecological factors, and differed in their abilities to portray the effects of human disturbances on macroinvertebrate communities. Taxonomic distinctness indices performed best, with the highest amount of variation associated to local stressors and hardly any variation explained by other factors, implying that these indices are robust in portraying human disturbances in streams. However, species diversity and functional diversity indices were also affected by spatial processes and climatic factors, suggesting that these indices should be used with caution in bioassessment. We hence conclude that environmental assessment of riverine ecosystems should not rely entirely on the perspective of species sorting. In contrast, both roles of spatial processes and environmental variables related to human disturbances and climatic variation should be incorporated in management and conservation of riverine ecosystems.
... 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.
... Application of functional approaches in biomonitoring has other advantages. Although fauna may possess different states of a functional trait, most fauna express the same traits across the world, making traitbased structure of assemblages comparable across the multiple geographical regions, while taxonomic composition of assemblages may be regionally dependent and results of taxonomic approaches may not be comparable among different localities (Göthe et al., 2017;Heino, 2011). Many functional traits are considered as indicators of ecosystem functions. ...
... Such results are in accordance with the findings in previous studies (e.g. Dolédec et al., 2006;Göthe et al., 2017;Guilpart et al., 2012;Li et al., 2019). Indeed, the assemblage variation of taxonomy-based composition provides implications for monitoring and assessment programs. ...
... 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.
... The goodness of fit for each nutrient factor was estimated by applying the envfit function with 999 permutations. Variance partitioning analysis (VPA) was performed using Vegan package (version 2.5-3) in R to determine the relative contributions of C-factor (DOC), N-factor (TN, NO 3 − , and NH 4 + ), P-factor (TP and SRP), and the interactions of these factors (C × N, C × P, N × P, and C × N × P) [4,63]. t-tests were used to compare the differences of various parameters between different seasons. ...
Article
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Seasonal water level fluctuations (WLFs) impose dramatic influences on lake ecosystems. The influences of WLFs have been well studied for many lake biotas but the microeukaryotic community remains one of the least-explored features. This study employed high-throughput 18S rRNA gene sequencing to investigate the spatiotemporal patterns of microeukaryotic communities in the dry and wet seasons with concomitant change of nutrients in Poyang Lake, which experiences huge seasonal WLFs. The results showed that the dry season and wet season had distinct microeukaryotic community compositions and structures. In the dry season, Ciliophora (13.86–40.98%) and Cryptomonas (3.69–18.64%) were the dominant taxa, and the relative abundance of these taxa were significant higher in the dry season than wet season. Ochrophyta (6.88–45.67%) and Chlorophyta (6.31–22.10%) was the dominant taxa of microeukaryotic communities in the wet season. The seasonal variation of microeukaryotic communities was strongly correlated to seasonal nutrient variations. Microeukaryotic communities responded significantly to dissolved organic carbon, total nitrogen, nitrate, and soluble reactive phosphorus in the dry season, and correlated to nitrate and total phosphorus in the wet season. The microeukaryotic community showed different modular structures in two seasons, and nutrient variations were the key factors influencing seasonal variations of the modular structures. Moreover, microeukaryotic community networks based on different seasons indicated that the microeukaryotic community co-occurrence patterns were not constant but varied largely associating with the nitrogen and phosphorus variations under the effects of WLFs. Our results are important for understanding how microeukaryotic communities respond to nutrient variation under seasonal water level fluctuation.
... 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 the current distributions and biodiversity of stream taxa might change under mitigated, stabilizing and increasing greenhouse gas emissions. Location Conterminous USA. 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 1,227 distinct stream localities using water chemistry, watershed and climatic variables. Models based only on climate were used to project changes in the distributions and biodiversity of cold‐ versus warm‐water taxa under representative concentration pathways (RCPs) ranging from 2.6 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. The RCP‐based projections suggested a widespread expansion of warm‐water taxa, outpacing the decline of cold‐water taxa. Consequently, overall species richness would increase, but beta diversity would decrease drastically with the severity of climate change. A closer look at individual taxa and functional guilds revealed that vulnerable cold‐water taxa included: (a) diatom guilds forming the base and bulk of the biofilm; (b) environmentally sensitive insects, characteristic of unimpacted streams; and (c) ecologically and recreationally important salmonids, which were forecast 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 impacts of climate change on stream ecosystems, with the 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. Given that the magnitude of these biotic shifts depends on the severity of climate change, appropriate current policy decisions are necessary to preserve freshwater ecosystems.
... This is usually done by analysing relationships between community metrics, environmental site characteristics and spatial distance or connectivity between sites (e.g. Cauvy-Fraunié et al., 2015;Göthe et al., 2017;Schmera et al., 2018;), and the relative importance of environmental versus spatial factors may change among different habitat types Sarremejane et al., 2017). Beta diversity, the dissimilarity between communities, is the metric used to study these processes. ...
Article
We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudinal patterns in richness and community composition between main stem and tributary sites, and 2) to determine the relative importance of the replacement and richness difference component for overall beta diversity and of environmental versus spatial distance on beta diversity among main stem and tributary sites. In total 138 taxa were identified. There were no differences between main stem and tributary sites in mean abundance or taxon richness (67 and 58, respectively). A nMDS and ANOSIM based on Bray-Curtis similarities found no separation of main stem and tributary sites, but that upper (≥880 m a.s.l) and lower sites (≤680 m a.s.l.) formed two different groups. In both main stem and tributaries taxon richness increased only slightly going downstream while the community composition (DCA1) was much better explained by altitude and distance from source. Overall, beta diversity (Sørensen and Bray-Curtis dissimilarity) was similar for the two groups, and total Sørensen dissimilarity was driven mainly by replacement in main stem (78 %) and tributary sites (77 %). Mantel tests showed that main stem dissimilarities were significantly correlated to environmental PCA distance, watercourse distance, overland distance and altitudinal differences. Tributary dissimilarities were not correlated to any of these four factors. GLMs showed that dissimilarity among main stem sites was explained only by altitude difference, while no factors were significant among tributary sites, even though nearly so for environmental PCA distance. The study illustrates the importance of measuring beta diversity along ecological gradients, such as river continua and/or altitudinal gradients, where alpha diversity may fail to detect relatively minor changes in assemblage composition. Such changes are likely to occur due to present and future climate warming.
... Our results suggest that, in the Middle Paraná River, dispersal is not limiting for aquatic dispersers. This aligns with current ideas about metacommunity organization in large rivers (Brown & Swan 2010) where, unlike headwaters, high connectivity among sites promotes high dispersal of organisms (Göthe et al. 2013;Göthe et al. 2017;Schmera et al. 2018). ...
Article
Metacommunity theory is a mechanistic framework that explains the interdependence of local factors and regional processes as community drivers. Recent evidence suggests that dispersal mode is a key trait that potentially affects metacommunity dynamics. We analyzed the distribution patterns of benthic macroinvertebrates with different dispersal modes in the Middle Paraná, a neotropical large river. We assessed the relative importance of local environmental conditions and regional spatial structure as assemblage drivers. Aquatic and aerial dispersers presented Clementsian and Gleasonian structures, respectively. For both groups, local environmental conditions influenced community assembly, and spatial structure (overland distances) also affected the distribution of aerial dispersers. Our study highlights that the role of spatial structure as a driver of benthic metacommunities depends on species' dispersal modes. Aerial dispersers responded to regional spatial variables and it is likely that these organisms are also influenced by mass effects. Our results are consistent with current ideas of metacommunity dynamics in large rivers, where dispersal is not considered to limit the distribution of benthic organisms.
... In general, the RCC supports a species-sorting paradigm of stream macroinvertebrate community structuring, due to the dominance of environmental heterogeneity, in the form of POM and light availability and in structuring local communities (de Mendoza et al. 2017). Yet, how this varies over taxonomic groups and diverse stream conditions, influencing dispersal capability, remains an active area of study (Göthe et al. 2017). ...
Article
The River Continuum Concept (RCC) is a milestone in stream ecology because of its comprehensive evaluation of the structure and function of lotic ecosystems. Linking stream physical and geo-morphological attributes with patterns in biodiversity, functional traits, and metabolism dynamics, this theory describes downstream gradients in community composition and ecosystem processes. The aim of this review is to evaluate how the RCC, 40 years from its publication in the Canadian Journal of Fisheries and Aquatic Sciences, has influenced basic and applied research in stream ecology, focusing on the most important contributions and recent developments. This work puts into perspective the historical significance of the RCC in the scientific process and integrates past and recent theories including metacommunity and metaecosystem theories and the river network perspective to predict taxonomic and functional diversity of benthic communities. Thus, this review provides a unifying overview of the historical context of the field for exploring basic and applied ecological questions to the next generation of stream ecologists.
... Mechanistic methods often attempt to distinguish different metacommunity models through the partitioning of spatial and environmental variables, for instance, using the significance of the variance partitions of environment and spatial variables to be indicative of a metacommunity model (e.g. Grönroos et al., 2013;Göthe et al., 2016;Tolonen et al., 2016). In contrast, the pattern-based approach called Elements of metacommunity structure (EMS) analyses the characteristics of species distributions that may emerge as a result of underlying environmental gradients, and manifest as particular metacommunity structures. ...
Article
• Understanding processes driving patterns of species distribution and diversity is one of the main objectives of community ecology. • The aim of our study was to evaluate the spatial variation in assemblage composition of stream‐dwelling macroinvertebrates and identify which factors (e.g. water quality, land cover) are the most important drivers. • We applied the elements of the metacommunity structure approach on a dataset of 38 communities from the Futaleufú basin in northwestern Patagonia. To better understand assemblage variation, we deconstructed our macroinvertebrate dataset into different taxonomic and trait groups. We then identified the most influential factors driving community composition using random forests. • We found that half of our datasets (i.e. macroinvertebrate groups) exhibited a nested structure with clumped species loss, while the other half showed a quasi‐nested pattern with either clumped or stochastic species loss. • Overall, water quality was the most important driver of community variation, although climate, geography, and land cover were more or less relevant in particular cases. We found differences in the relative importance of the selected explanatory variables among datasets. This would suggest that different components of the macroinvertebrate community respond differently to environmental factors. • Our findings could be of value for conservation planning, as they suggest that preserving the most species‐rich streams would, to some extent, guarantee the conservation of the entire species pool.
... In fact, actual dispersal may be limited even for species with high dispersal capacities (Jenkins & Underwood, 1998;Bohonak & Jenkins, 2003). The dispersal rates of individual taxa with potentially different dispersal abilities may be indirectly deduced from multiple comparisons of their spatial structure (Beisner et al., 2006;Hájek et al., 2011;Grönroos et al., 2013;Padial et al., 2014;Rádková et al., 2014;Heino et al., 2015b;Göthe et al., 2017). Unfortunately, these studies failed to account for meiofauna. ...
Article
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The metacommunity concept incorporates spatial dynamics into community ecology, shedding light on how local and regional processes interact in structuring ecological communities, and to which measure they are deterministic or stochastic. We reviewed metacommunity studies on freshwater meiobenthos published since 2004, when the main principles of metacommunity theory were conceptualized. The studies (together 19) were observational, focused mainly on ostracods, and rarely on rotifers and nematodes. In accordance with general expectations, the prevalent structuring force was species sorting. Ostracods showed more dispersal limitations than nematodes and rotifers, and there was very little support for dispersal surplus. We discussed the role of body size, dispersal mode, and attachment to sediment for the meiofauna dispersal. Effects of metacommunity context (habitat connectivity, spatial extent, and environmental heterogeneity), study design (e.g., sample size), and statistical approach could not be sufficiently disentangled due to the low number of studies. Local stochasticity, consistent with neutral theory and patch dynamics, was indicated for taxa with weak specialization and metacommunities in small habitats. Our understanding of meiofaunal metacommunities is only fragmentary and it would highly benefit from direct comparisons of taxa with different species traits and between different spatial scales, and studies incorporating temporal dynamics and hypothesis-driven experiments.
... In such cases, the species obtained a value in between the ranked categories (i.e. 1.5 and 2.5), following Göthe et al. (2017). However, we decided to weight value 2, which indicates the presence of the attribute, at the expense of value 1, which indicates the occasional, but not general exhibition of the attribute. ...
Article
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Functional homogenisation occurs across many areas and organism groups, thereby seriously affecting biodiversity loss and ecosystem functioning. In this study, we examined how the functional features of aquatic macrophytes have changed during a 70-year period at community and species levels in a boreal lake district. At the community level, we examined if aquatic macrophyte communities showed different spatial patterns in functional composition and functional richness in relation to main environmental drivers between the time periods. We also observed each species in functional space to assess if species with certain sets of traits have become more common or rare in the 70-year study period. We found changes in the relationship between functional community composition and the environment. The aquatic macrophyte communities showed different patterns in functional composition between the two time periods, and the main environmental drivers for these changes were partly different. Temporal changes in functional richness were only partially linked to the concomitant changes in the environment, while stable factors were more important. Species functional traits were not associated with commonness or rarity patterns in the study period. Our findings revealed that functional homogenisation has not occurred across these boreal lakes, ranging from small oligotrophic forest lakes to larger lakes affected by human impacts.
... To determine an indirect measure of dispersal, the distances between pools were considered explanatory variables along with predation and environmental variables (Beisner, Peres-Neto, Lindstrom, Barnett, & Longhi, 2006;Göthe et al., 2017;Jacobson & Peres-Neto, 2010). We determined the distances between pools within sites and among sites following the riverine network by marking the geographical coordinates in the centre of each pool and then calculating the pairwise distances between the sites using a GIS (QGIS Development Team, 2016). ...
Article
Metacommunity theory is a new approach for explaining how local and regional processes contribute to community organisation and integrative studies are needed to fully characterise the processes underlying its structure and function. We analysed, through variation partitioning and distance decay relationships, how metacommunities of fish in pools of intermittent rivers are structured by environmental, species interaction and spatial factors. The results indicate that both species sorting and dispersal limitation (spatial factors) were important in shaping fish metacommunities. Species sorting was the most influential driver within fish metacommunities, but predation was much less relevant and did not show any pure effect in metacommunity structure. However, environmental factors were determinant among metacommunity patches.
... Given that a trait is assumed to reflect the mechanistic link between species and environmental variation (Göthe et al., 2017;Schmera et al., 2017), the composition of macroinvertebrate communities in dammed rivers could be portrayed by relevant traits of species (Martínez et al., 2013;Van Looy et al., 2014;Belmar et al., 2019;Bruno et al., 2019;Ruhi et al., 2018). The frequent release of either warm water or cold water, changes in flow regime, dissolved oxygen and other variables at downstream sites can set up a novel environmental filter selecting species with corresponding traits for living in downstream sites (Bruno et al., 2019). ...
Article
Understanding ecological processes that drive metacommunity dynamics is essential for elucidating the mechanisms of community assembly and for guiding biodiversity conservation. This is especially important in dammed rivers. Here, we examined the taxonomic and functional beta diversity of macroinvertebrates and their underlying drivers in a dammed tropical river and compared the patterns with those in an adjacent undammed river. We found that both taxonomic and functional beta diversities were higher in the dammed river than in the undammed river across wet and dry seasons. The replacement component contributed most to the overall beta diversity for both taxonomic and functional facets, and this component was higher in the dammed river than in the undammed river. In addition, the taxonomic richness difference component was significantly higher in the dammed river in the dry season, but the functional richness difference component showed no difference between the two rivers and between the two seasons. Environmental filtering was the primary driver of total beta diversity and its replacement component, whereas the richness difference component was mainly explained by spatial factors, but these drivers varied in the dammed river in different seasons. Overall, our results indicated that damming induced changes in physiochemical variables (e.g., temperature, conductivity, and nutrients), accompanied by alterations in flow regime and longitudinal connectivity, increased replacement and loss of taxa or traits. These changes have consequently led to alteration of macroinvertebrate taxonomic and functional community dissimilarity and affected the relative effects of environmental and spatial factors on beta diversity and its components. Our study helps understand the ecological processes associated with dam impacts on macroinvertebrate biodiversity and the conservation potential of undammed rivers. In addition, our results showed that taxonomic and functional beta diversities can provide complementary information about dam impacts on riverine biodiversity.
... 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.
... 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.
... 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 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. ...
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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.
... 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.
... 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). ...
... 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. ...
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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. ...
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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. ...
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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.
... 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
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 ponds biodiversity surrogates, two questions lead to this work: How do wetland plant species assemblages and abundance vary across local‐scale and regional‐scale classification schemes of wetlands? How does wetland plant beta diversity vary within these wetland classification schemes? Western Patagonia, Argentina, from 36° to 56° S and from 73° to 65° W. 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 plant composition variation. Also, an IndVal analysis was carried out to detect the taxa with the highest association values (indicator taxa) to the different categories of wetland classifications. Beta diversity was calculated to evaluate variation patterns within classification schemes. Plant distribution was mainly related to site location on the latitudinal gradient, following a decreasing pattern of air temperature from northern to southern wetlands. The 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 rest, sustaining the highest number of indicator taxa. Wetland plant beta diversity patterns were explained by relatively high species turnover, with species compositions showing low nestedness values. 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 Patagonian Andes and those with 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 maintain the ecosystem services that they provide.
... 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.
Article
The use of deconstructive approaches, such as functional classification models, can be an important tool for understanding aquatic systems. This study aimed to evaluate the distribution and community structure of mixotrophic flagellates in lakes of four large Brazilian floodplain systems, those of Amazon River, Araguaia River, Pantanal and upper Paraná River, in contrasting hydrological periods. A partial redundancy analysis (pRDA) was used to estimate the relative roles of environmental, spatial and biogeographic factors on both the entire community and a deconstructive approach using Reynolds' mixotrophic flagellate functional groups (RFGs). High environmental variability was found between the rainy and dry periods, mostly for the Amazon floodplain system. We identified 135 taxa and seven RFGs of mixotrophic flagellates: E, Lo, Q, W1, W2, Ws and Y. A permanova evidenced that biomass of mixotrophic flagellate RFGs reflected differences among floodplains and between hydrological periods. Our results showed that the use of RFGs better summarises the mixotrophic phytoplankton metacommunity structure when compared to the use of the entire community. The pRDA showed that explanatory matrices explained up to 37% of variation in the community. Environmental, spatial and biogeographic factors were important to explain the structure of the mixotrophic flagellates; however, the importance of the different components seemed to depend on the hydrological period and the traits of each RFG.
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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Freshwater-fish diversity declined rapidly due to multiple anthropogenic disturbances. The loss of fish diversity often manifested itself in taxonomic homogenization over time. Knowledge of multi-faceted diversity (i.e., species, functional, and phylogenetic diversity) perspectives is important for biodiversity assessment and conservation planning. Here, we analyzed the change of the species diversity and phylogenetic diversity of fish in 2008 and 2021 as well as explored the driver factors of the biodiversity patterns in the Lushan National Nature Reserve. The results showed that the species diversity and phylogenetic diversity of fish have declined from 2008 to 2021, with five species lost over time. We found an overall homogenization trend in the fish fauna of the study area, with a 4% increase in taxonomic similarity among the rivers. Additionally, we found that community structure of fish was significantly different among the rivers, and environmental filtering was the main contributor to the phylogenetic diversity of fish in 2008 and 2021. This study provides new insight into the patterns and drivers of fish-biodiversity change in the broader Yangtze River basin and informs management efforts.
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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 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.