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As alien invasive species are a key driver of biodiversity loss, understanding patterns of rapidly changing global species compositions depends upon knowledge of invasive species population dynamics and trends at large scales. Within this context, the Ponto-Caspian region is among the most notable donor regions for aquatic invasive species in Europe. Using macroinvertebrate time series collected over 52 years (1968–2020) at 265 sites across 11 central and western European countries, we examined the occurrences, invasion rates, and abundances of freshwater Ponto-Caspian fauna. We examined whether: (i) successive Ponto-Caspian invasions follow a consistent pattern of composition pioneered by the same species, and (ii) Ponto-Caspian invasion accelerates subsequent invasion rates. In our dataset, Ponto-Caspian macroinvertebrates increased from two species in 1972 to 29 species in 2012. This trend was parallelled by a non-significant increasing trend in the abundances of Ponto-Caspian taxa. Trends in Ponto-Caspian invader richness increased significantly over time. We found a relatively uniform distribution of Ponto-Caspian macroinvertebrates across Europe without any relation to the distance to their native region. The Ponto-Caspian species that arrived first were often bivalves (46.5% of cases), particularly Dreissena polymorpha, followed secondarily by amphipods (83.8%; primarily Chelicorophium curvispinum and Dikerogammarus villosus). The time between consecutive invasions decreased significantly at our coarse regional scale, suggesting that previous alien establishments may facilitate invasions of subsequent taxa. Should alien species continue to translocate from the Ponto-Caspian region, our results suggest a high potential for their future invasion success highly connected central and western European waters. However, each species’ population may decline after an initial ‘boom’ phase or after the arrival of new invasive species, resulting in different alien species dominating over time., This study was supported by the Grant Agency of the University of South Bohemia, project number 065/2022/Z. R.N.C. acknowledges funding from the Leverhulme Trust Early Career Fellowship (ECF-2021-001). We also acknowledge Flanders Environment Agency for providing the publicy available data. P.H. and P.J.H. received funding from the EU Horizon 2020 project eLTER PLUS (Grant Agreement No. 871128). NB and MC were supported by the Serra-Hunter programme (Generalitat de Catalunya). MC was also supported by a Ramón y Cajal contract funded by the Spanish Ministry of Science and Innovation (RYC2020-029829-I). NB was also supported by the H2020 European Research and Innovation action Grant Agreement no. 869226 (DRYvER). The FEHM (Freshwater Ecology, Hydrology and Management) research group (to which NB and MC belong) was funded by the “Agència de Gestió d’Ajuts Universitaris i de Recerca” (AGAUR) at the "Generalitat de Catalunya” (2017SGR1643). BG was funded through the 2017–2018 Belmont Forum and BIODIVERSA joint call for research proposals, under the BiodivScen ERANet COFUND programme, funded through the Spanish State Research Agency (MCI/AEI/FEDER, UE, PCI2018-092986).

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) Fundacao de Apoio a Pesquisa do Distrito Federal (FAPDF), Fundacao de Amparo a Pesquisa do Estado do Amazonas (FAPEAM), BIODIVERSA/FAPEAM, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ), Bundesministerium fuer Bildung und Forschung, Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES), FAPEAM-Program POSGRAD, Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG), INPA/MCTI 465540/2014-7, Leibniz Competition 0621187/2017, Leibniz-Gemeinschaft R20F0002, Instituto Nacional de Pesquisas da Amazpnia, unidade de~pesquisa Ministerio da Ciencia, Tecnologia e Inovacoes (INPA/MCTI) 403758/2021-1, Programa Peixe Vivo of the Companhia Energetica de Minas Gerais 033W034A, Royal Society of New Zealand, Tertiary Education Commission, Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Foundation for Science and Technology, Associate LaboratoryARNET J45/2018, CEEC

Understanding the capacity of ecological systems to withstand and recover from disturbances is a major challenge for ecological research in the context of environmental changes. Past research has mostly focused on the local effects of disturbances on biodiversity recovery, while alterations of inter-patch connectivity induced by disturbances have received comparatively less attention. Here, we investigated the effect of disturbances on local biodiversity recovery within metacommunities. Our specific focus was on drying river networks, which are characterised by a high variability of patch connectivity. We found marked variations of local biodiversity recovery among sites and among groups of organisms with contrasting dispersal modes, which were explained by the amount of patch connectivity loss due to drying events. Local communities of flying organisms recovered more efficiently from drying events than organisms with strictly aquatic dispersal due to the capacity of the former group to overcome hydrological connectivity loss. As a general rule, loss of patch connectivity decreases community recovery, regardless of patch location in the river network, dispersal mode or drying spatial extent. The relationship between patch connectivity loss and community recovery we found in river networks is general and applicable to any spatial network with a high variability of patch connectivity.

Regional-scale ecological processes, such as the spatial flows of material, energy, and organisms, are fundamental for maintaining biodiversity and ecosystem functioning in river networks. Yet these processes remain largely overlooked in most river management practices and underlying policies. Here, we propose adoption of a meta-system approach, where regional processes acting at different levels of ecological organization - populations, communities, and ecosystems - are integrated into conventional river conservation, restoration, and biomonitoring. We also describe a series of measurements and indicators that could be assimilated into the implementation of relevant biodiversity and environmental policies. Finally, we highlight the need for alternative management strategies that can guide practitioners toward applying recent advances in ecology to preserve and restore river ecosystems and the ecosystem services they provide, in the context of increasing alteration of river network connectivity worldwide.

As alien invasive species are a key driver of biodiversity loss, understanding patterns of rapidly changing global species compositions depends upon knowledge of biological invasion dynamics and trends. The Ponto-Caspian region is among the most notable donor regions for aquatic invasive species in Europe. Using macroinvertebrate time series collected over 52 years (1968–2020) at 265 sites across 11 European countries, we examined the occurrences, invasion rates and interspecific interactions of freshwater Ponto-Caspian fauna, as well as biotic homogenization trends in European waterways. According to our data, Ponto-Caspian macroinvertebrates increased from two species in 1972 to 29 species in 2012 and we found a greater richness of invading Ponto-Caspian macroinvertebrates in datasets collected closer to the source region. This may reflect dispersal lag times, indicating that more distant sites will be increasingly invaded in the future. The pioneering Ponto-Caspian species that arrived first were often bivalves (46.5% of cases), particularly Dreissena polymorpha, followed secondarily by amphipods (83.8%; primarily Chelicorophium curvispinum and Dikerogammarus villosus). With increasing invasions, the time between consecutively-appearing invaders decreased six-fold, indicating potential facilitations that improved invasion success of subsequent taxa. We detected a negative relationship between the abundance trends of the first and second Ponto-Caspian macroinvertebrate species, suggesting that interactions between these species are asymmetrical, with the initial invader facilitating the subsequent invader at the potential cost of its own population growth rate. Lastly, we found that macroinvertebrate communities became increasingly similar over time. European invasion rates from the Ponto-Caspian region suggest a high potential for future invasions from this region, with more hotspots and donor regions likely emerging.

Made available in DSpace on 2021-06-25T10:32:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Biodiversity is structured in space and time, yet our understanding about the temporal variation of biological communities is still limited. Recent work suggests that temporal β diversity should be lowest in unpredictable systems with low seasonality, as expected for tropical ecosystems. However, this hypothesis remains largely unexplored. Here, we analysed the temporal dynamics of Atlantic Forest coastal stream caddisfly assemblages sampled simultaneously along four years, resulting in 99 unique site-time combinations. Given that the region we studied is expected to have low climatic seasonality and low environmental harshness, we expected to find: (1) unseasonal variation in community composition; (2) equal contribution of nestedness and turnover to β diversity; (3) weak correlation between variation in community composition and in environmental variables; and (4) temporal β diversity similar to that expected by neutral dynamics. Using wavelet analysis we found that, in spite of general temperature stability, precipitation was highly seasonal but unpredictable at the monthly scale. We found high temporal β diversity, with a larger contribution of nestedness due to an overall decrease in abundance and diversity during months characterised by heavy rain events. We also found that community composition was moderately structured in space, suggesting that both local in-stream characteristics and dispersal limitation drive community reassembly after heavy rain events. Null model analysis indicated that observed short-term β diversity was not distinct from that expected by chance (i.e. produced by null simulations). This suggests an important role of stochastic colonisation and dispersal limitation in the temporal organisation of Atlantic Forest stream assemblages. Since heavy rain events strongly disassemble communities that are then randomly recolonised, and considering the current scenario of climate change, increased extreme events of precipitation could lead to unpredictable changes in biodiversity in tropical regions. Environmental Sciences Department Federal University of São Carlos (UFSCar) Museum of Zoology of the University of São Paulo Freshwater Ecology Hydrology and Management (FEHM) Research Group Departament de Biologia Evolutiva Ecologia i Ciències Ambientals Facultat de Biologia Institut de Recerca de l’Aigua (IdRA) Universitat de Barcelona (UB) Freshwater Ecology Hydrology and Management (FEHM) Research Group Departament de Biologia Evolutiva Ecologia i Ciències Ambientals Facultat de Biologia Institut de Recerca de la Biodiversitat (IRBio) Universitat de Barcelona (UB) Institute of Biosciences São Paulo State University (UNESP) Institute of Biosciences São Paulo State University (UNESP)

Given the multiple stressors affecting freshwater ecosystems and the limited resources devoted to their management, effective conservation of freshwater biodiversity requires regional prioritization. Patagonian wetlands are essential for regional biodiversity and the economy, but they are still far from reaching global conservation targets and many of them could disappear due to climate change. Our study aimed at prioritizing wetlands based on aquatic and terrestrial biodiversity, their conservation status and vulnerability to climate change. First, we identified 43 priority wetlands containing all aquatic biodiversity collected in 82 Patagonian wetlands located over a 1500 km north–south gradient, by using the software Marxan. Then, we ranked within priority wetlands according to their conservation status (low priority if they were already protected; medium priority if not), importance for terrestrial biodiversity conservation (high priority) and vulnerability to climate change. Highly ranked priority wetlands in National Parks (low priority), contained diverse wetlands (57% aquatic taxon richness), including a large proportion of rare species (33%). High priority wetlands are oases of water in an arid and semiarid steppe, containing not only a large proportion of the aquatic biodiversity, but also acting as a refuge for terrestrial flora and fauna. Different management actions are proposed according to wetland priority level (e.g. fencing, creation of artificial ponds), and since 20% of medium priority and 36% of high priority wetlands are expected to disappear by 2050, their inclusion in conservation or restoration plans needs to be carefully evaluated.

AIM: Changes in land use and cover (hereafter land use) affect freshwater ecosystems at different spatial scales. We tested the effects of land use on the dispersal capacity of stream macroinvertebrates through local and regional processes. LOCATION: In all, 183 Brazilian headwater stream sites, located in the Neotropical Savanna with variable land use and covering a total area of 46,394 km². TAXON: Stream macroinvertebrates METHODS: We used multiple regression models for distance matrices to identify the relative importance of environmental and landscape characteristics to explain community dissimilarity of stream macroinvertebrates with different mobility traits. As predictors, we calculated four distance metrics: environmental distance describing the dissimilarity in local conditions, the network distance accounting for distances across the drainage system and two distances measuring landscape resistance to dispersal (topographic and land use). We classified macroinvertebrates in dispersal groups according to their dispersal abilities (flying and drifting) and life story traits (voltinism, adult life span and body size). We tested the effects of these distances on all taxa and on the different dispersal groups, to explore whether biological traits would result in different metacommunity patterns. RESULTS: Our hierarchical clustering analysis identified five macroinvertebrate dispersal groups. The dispersal group 1 was mainly composed by aquatic obligate taxa, dispersal group 2 by taxa with low drift propensity, dispersal group 3 represented taxa with high directional flight capacity, dispersal group 4 included taxa with medium drift propensity and dispersal group 5 represented taxa with high drift propensity. We found that environmental distance and land use distance were the most important predictors explaining community dissimilarity for most of the dispersal groups. MAIN CONCLUSION: The metacommunity patterns found in this study suggest that environmental filtering was the most important community assembly mechanism at a local scale, whereas land use could constrain dispersal at the regional scale. Understanding these processes is crucial to meet conservation and restoration goals, especially in biodiversity hotspots. Our results reinforce the importance of considering entire catchments for preserving stream health and aquatic biodiversity and indicate the need for a much more integrative research between terrestrial and aquatic ecology.

International audience; Aim To analyse temporal metacommunity dynamics in river networks in relation to hydrological conditions and dispersal. Location Fifteen river reaches from the Llobregat, Besos and Foix catchments in the North-Eastern Iberian Peninsula. Taxon Aquatic macroinvertebrates belonging to 99 different families. Methods We sampled aquatic macroinvertebrate communities during spring in 20 consecutive years. We built two environmental distances (one related with water chemistry and another one with river flow regime) and two spatial distances (network distance and topographic distance). Then we used Mantel tests (accounting for spatial autocorrelation) to relate macroinvertebrate dissimilarity with environmental and spatial distances. Additionally, we determined the dry and wet years using the Standardized Precipitation Index (SPI) and we classified macroinvertebrate families based on their ability to fly and to drift. Finally, we ran a linear regression model including the correlation value (r) of each Mantel test as response variable and distance type (environmental or spatial), SPI, dispersal mode, their pairwise interactions and a three-way interaction as predictor variables. Results Metacommunity organization varied over time and it was significantly affected by precipitation, which can be related to river network connectivity. The environmental filters, mainly the flow regime, were generally more important than the spatial filters in explaining community dissimilarity over the study period. However, this depended on the dispersal abilities of the organisms. Network fragmentation due to flow intermittence during the dry years significantly reduced the dispersal capacity of strong aerial dispersers, leading to spatially structured metacommunities. For strong drift dispersers, community dissimilarity patterns were generally best explained by environmental filters regardless of SPI. Main conclusions A significant temporal variation in metacommunity organization can be expected in highly dynamic systems (e.g. Mediterranean rivers) and it might depend on the dispersal modes and abilities of the organisms, since they determine the response to changes in environmental and landscape filters.

Rapid shifts in biotic communities due to environmental variability challenge the detection of anthropogenic impacts by current biomonitoring programs. Metacommunity ecology has the potential to inform such programs, because it combines dispersal processes with niche-based approaches and recognizes variability in community composition. Using intermittent rivers—prevalent and highly dynamic ecosystems that sometimes dry—we develop a conceptual model to illustrate how dispersal limitation and flow intermittence influence the performance of biological indices. We produce a methodological framework integrating physical- and organismal-based dispersal measurements into predictive modeling, to inform development of dynamic ecological quality assessments. Such metacommunity-based approaches could be extended to other ecosystems and are required to underpin our capacity to monitor and protect ecosystems threatened under future environmental changes.

Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation. ispartof: ECOLOGY LETTERS vol:25 issue:2 pages:255-263 ispartof: location:England status: published

International audience; As complex mosaics of lotic, lentic, and terrestrial habitats, intermittent rivers and ephemeral streams (IRES) sup-port high biodiversity. Despite their ecological importance, IRES are poorly represented in routine monitoring programs, but recent recognition of their considerable-and increasing-spatiotemporal extent is motivating ef-forts to better represent IRES in ecological status assessments. We examine response patterns of aquatic macro-invertebrate communities and taxa to flow intermittence (FI) across three European climatic regions. We used self-organizing map (SOM) to ordinate and classify sampling sites based on community structure in regions with continental, Mediterranean and oceanic climates. The SOM passively introduced FI, quantified as the mean annual % flow, and visualized its variability across classified communities, revealing a clear association be-tween community structure and FI in all regions. Indicator species analysis identified taxa indicative of low, inter-mediate and high FI. In the continental region, the amphipod Niphargus was indicative of high FI and was associated with groundwater-fed IRES, whereas indicators of Mediterranean IRES comprised Odonata, Coleop-tera and Heteroptera taxa, which favor lentic conditions. In the oceanic region, taxa indicative of relatively high FI included leuctrid stoneflies anda limnephilid caddisfly, likely reflecting the colonization of IRES by aerial adults from nearby perennial reaches. The Diptera families Chironomidae and Simuliidae showed contrasting FI preferences among regions, reflecting environmental heterogeneity between regions and the coarse taxonomic resolution to which these organisms were identified. These region-specific community and taxon responses of aquatic biota to FI highlight the need to adapt standard biotic indices to enable effective ecological status assessments in IRES.

Evaluating data quality and inventory completeness must be a preliminary step inany biodiversity research, particularly in the case of insects and high biodiversityareas. Yet, this step is often neglected or, at best, assessed only for one insectgroup, and the degree of congruence of sampling effort ffor different insect groupsremains unexplored. We assess the congruence in the spatial distribution of sampling effort for fiveinsect groups (butterflies, caddisflies, dung beetles, moths, and aquatic beetles) inthe Iberian Peninsula. We identify well-surveyed areas for each taxonomic groupand examine the degree to which the patterns of sampling effort can be explainedby a set of variables related to environmental conditions and accessibility. Irrespective of the general lack of reliable inventories, we found a general but lowcongruence in the completeness patterns of the different taxa. This suggests thatthere is not a common geographical pattern in survey effort and that idiosyncraticand contingent factors (mainly the proximity to the workplaces of entomologists)are differentially affecting each group. After many decades of taxonomic and faunistic work, distributional databases ofIberian insects are still in a very preliminary stage, thus limiting our capacity toobtain reliable answers to basic and applied questions. We recommend carrying out long-term, standardised and well-designed entomolog-ical surveys able to generate a reliable image of the distribution of different insect groups. This will allow us to estimate accurately insect trends and better under-stand the full extent of global biodiversity loss., This study has been supported by the projects BioWeb (MINECO:CGL2011-15622-E BOS), BANDENCO (JCMM: POII11-0277-5747)and IBERARTRO (SBPLY/17/180501/000492) founded by European Regional Development Fund (ERDF) through the Consejería de Educación, Ciencia y Cultura, Junta de Comunidades de Castilla-La Mancha. David Sánchez-Fernández is funded by a postdoctoral contract fromthe Spanish Ministry of Science and Innovation (Ramón y Cajal program; RYC2019-027446-I

Understanding the capacity of ecological systems to withstand and recover from disturbances is a major challenge for ecological research in the context of environmental change. Disturbances have multi-scale effects: they can cause species extinctions locally and alter connectivity between habitat patches at the metacommunity level. Yet, our understanding of how disturbances influence landscape connectivity remains limited. To fill this gap, we develop a novel connectivity index that integrates the temporal variation of patch connectivity induced by disturbances, which can be applied to any spatially-structured habitat. We then combine this index with a metacommunity model to specifically investigate biodiversity recovery from drying events in river network metacommunities. We demonstrate that patch connectivity explains variations of species richness between groups of organisms with contrasting dispersal modes and captures the effect of drying intensity (i.e., fraction of patches that dry-up) and drying location on community recovery. As a general rule, loss of patch connectivity decreases community recovery, regardless of patch location in the river network, dispersal mode, or drying intensity. Local communities of flying organisms maintained higher patch connectivity in drying river networks compared to organisms with strictly aquatic dispersal, which explained the higher recovery capacity of this group from drying events. The general relationship between patch connectivity and community recovery we found can be applied to any spatial network subject to temporal variation of connectivity, thus providing a powerful tool for biodiversity management in dynamic landscapes.

Humans have severely altered freshwater ecosystems globally, causing a loss of biodiversity. Regulatory frameworks, like the Water Framework Directive, have been developed to support actions that halt and reverse this loss. These frameworks use typology systems that summarize freshwater ecosystems into environmentally delineated types. Within types, ecosystems that are minimally impacted by human activities, i.e., in reference conditions, are expected to be similar concerning physical, chemical, and biological characteristics. This assumption is critical when water quality assessments rely on comparisons to type-specific reference conditions. Lyche Solheimet al. (2019) developed a pan-European river typology system, the Broad River Types, that unifies the nationalWater Framework Directive typology systems and is gaining traction within the research community. However, it is unknown how similar biological communities are within these individual Broad River Types. We used analysis of similarities and classification strength analysis to examine if the Broad River Types delineate distinct macroinvertebrate communities across Europe and whether they outperform two ecoregional approaches: the European Biogeographical Regions and Illies' Freshwater Ecoregions. We etermined indicator and typical taxa for the types of all three typology systems and evaluated their distinctiveness. All three typology systems captured more variation in macroinvertebrate communities than random combinations of sites. The results were similar among typology systems, but the Broad River Types always performed worse than either the Biogeographic Regions or Illies' Freshwater Ecoregions. Despite reaching statistical significance, the statistics of analysis of similarity and classification strength were low in all tests indicating substantial overlap among the macroinvertebrate communities of different types. We conclude that the Broad River Types do not represent an improvement upon existing freshwater typologies when used to delineate macroinvertebrate communities and we propose future avenues for advancement: regionally constrained types, better recognition of intermittent rivers, and consideration of biotic communities. This study was part of the GETREAL (Incorporating spatial and seasonal variability in community sensitivity into chemical risk assessment) project, which was funded by the European Chemical Industry Council long-range research initiative (CEFIC-LRi project ECO 50). Dénes Schmera was supported by the NKFIH K140352 and 471-3/2021 grants. Petr Pařil, Marek Polášek and Michal Straka were supported by the P505-20-17305S grant. We are grateful to the staff that collected and analyzed data for the AQEM (EU FP5, contract No: EVK1-CT1999- 00027), BIODROUGHT, STAR (EU FP5, contract No: EVK1-CT 2001-00089), and WISER (EU FP7, contract No 226273) projects and to the various water agencies that participated in the abiotic and biotic data collection and analysis.

International audience; Globalization has led to the introduction of thousands of alien species worldwide. With growing impacts by invasive species, understanding the invasion process remains critical for predicting adverse effects and informing efficient management. Theoretically, invasion dynamics have been assumed to follow an "invasion curve" (S-shaped curve of available area invaded over time), but this dynamic has lacked empirical testing using large-scale data and neglects to consider invader abundances. We propose an "impact curve" describing the impacts generated by invasive species over time based on cumulative abundances. To test this curve's large-scale applicability, we used the data-rich New Zealand mud snail Potamopyrgus antipodarum, one of the most damaging freshwater invaders that has invaded almost all of Europe. Using long-term (1979-2020) abundance and environmental data collected across 306 European sites, we observed that P. antipodarum abundance generally increased through time, with slower population growth at higher latitudes and with lower runoff depth. Fifty-nine percent of these populations followed the impact curve, characterized by first occurrence, exponential growth, then long-term saturation. This behaviour is consistent with boom-bust dynamics, as saturation occurs due to a rapid decline in abundance over time. Across sites, we estimated that impact peaked approximately two decades after first detection, but the rate of progression along the invasion process was influenced by local abiotic conditions. The S-shaped impact curve may be common among many invasive species that undergo complex invasion dynamics. This provides a potentially unifying approach to advance understanding of large-scale invasion dynamics and could inform timely management actions to mitigate impacts on ecosystems and economies.

The European Water Framework Directive (WFD) mandates to incorporate the participation of stakeholders and the general public in the development and updating of the river basin management plans. So far, the WFD implementation has been mainly focused on perennial rivers without considering temporary rivers properly, neither in biomonitoring programs nor participatory processes. This paper aims at adapting participatory processes in river basin management to enhance the inclusion of ecosystems with poor or no social recognition such as temporary rivers. To do so, we examined previous experiences of participatory processes conducted in the WFD and adapted them to propose and implement an approach for promoting stakeholders’ engagement in temporary rivers. The approach is based on a collaborative leadership, includes multiple participatory engagement mechanisms, uses future global change scenarios and the concept of ecosystem services at different stages of the process, and aims at involving stakeholders not only in the proposal of measures stage but in the diagnosis of the ecological status. It also includes an evaluation of participants’ satisfaction on the process. We tested our approach in temporary rivers from the Mediterranean region. We found that the combination of environmental education and citizen science activities, together with the inclusion of the ecosystem services concept, was the most useful way to raise awareness on the biodiversity and ecological value of temporary rivers and to promote stakeholders’ engagement. Workshops conducted during the diagnosis stage played an important role in both including stakeholders’ suggestions and increasing their knowledge on temporary rivers. Further, envisaging climate-related future scenarios allowed participants to incorporate measures that could tackle new and emerging pressures on these ecosystems. As future environmental changes will increase the proportion of rivers with temporary flow regimes, our approach can contribute to adapt current participatory processes to future needs., The study was supported by the LIFE + TRivers [LIFE13 ENV/ES/000341] project. DJ-C was supported by a Juan de la Cierva contract (FJCI-2017-34977) and the CLIMALERT project (PCIN-2017-068) of the Spanish Ministry of Science and Innovation. We acknowledge all the participants in our workshops: citizens, local environmental associations (i.e. SITRA, Salvem Gaià, Associació medioambiental La Sénia, Associació Hàbitats, Plataforma pel riu Siurana, Plataforma Sierra de Chiva, AEMS ríos con vida, Connecta Natura and Acció Ecologista-Agró), research institutions (i.e. UAB, IRTA and CIEF), private sector (i.e. Corriols i Riberes SL, Crearqció and Fundación Natural Life) and local municipalities (i.e. La Bisbal, Alcover, La Sénia and Cheste town councils, as well as Consorci de les Gavarres and Parc Natural Tinença Benifassà).

Freshwater ecosystems generally lack adequate protection. In this regard, defining clear and objective conservation criteria through public participation is extremely important, as it can greatly enhance the feasibility of the conservation plans by building credibility, salience, and legitimacy. This article presents an exercise of systematic freshwater conservation planning informed and validated by public participation using river protected areas (RPAs) in the Ebro catchment, Spain, as a case study. A public participation process was performed to define the conservation criteria that RPAs should meet, resulting in a detailed list of conservation features and constraints that were poorly covered by the present network of RPAs in Spain. The present network of RPAs failed to adequately protect aquatic biodiversity, as 48% of the taxa did not meet the conservation target, including seven species of vulnerable invertebrates and three of vulnerable fish. marxan was used to identify a minimum set of additional areas that would help to meet the conservation target by adequately representing all conservation features and by increasing the efficiency of the network of protected areas. When marxan was run without restrictions, none of the present RPAs was selected, suggesting that the current network of RPAs is not efficiently meeting the conservation demands expressed through public participation. Overall, this study shows that combining public participation and systematic conservation planning could result in more efficient and enhanced protection of freshwater ecosystems by integrating a wide variety of conservation preferences into the design of RPAs. Also, according to the results, having detailed and updated information on the distribution of invasive and endangered species, as well as increasing the frequency and spatial extension of ecological monitoring, are key to meeting the public demands of enhanced freshwater biodiversity protection and the preservation of sites with high ecological value.

Resilience in river ecosystems requires that organisms must persist in the face of highly dynamic hydrological and geomorphological variations. Disturbance events such as floods and droughts are postulated to shape life history traits that support resilience, but river management and conservation would benefit from greater understanding of the emergent effects in communities of river organisms. We unify current knowledge of taxonomic‐, phylogenetic‐, and trait‐based aspects of river communities that might aid the identification and quantification of resilience mechanisms. Temporal variations in river productivity, physical connectivity, and environmental heterogeneity resulting from floods and droughts are highlighted as key characteristics that promote resilience in these dynamic ecosystems. Three community‐wide mechanisms that underlie resilience are (a) partitioning (competition/facilitation) of dynamically varying resources, (b) dispersal, recolonization, and recruitment promoted by connectivity, and (c) functional redundancy in communities promoted by resource heterogeneity and refugia. Along with taxonomic and phylogenetic identity, biological traits related to feeding specialization, dispersal ability, and habitat specialization mediate organism responses to disturbance. Measures of these factors might also enable assessment of the relative contributions of different mechanisms to community resilience. Interactions between abiotic drivers and biotic aspects of resource use, dispersal, and persistence have clear implications for river conservation and management. To support these management needs, we propose a set of taxonomic, phylogenetic, and life‐history trait metrics that might be used to measure resilience mechanisms. By identifying such indicators, our proposed framework can enable targeted management strategies to adapt river ecosystems to global change.

The biomonitoring methods implemented by water authorities are mostly developed for perennial rivers, and do not apply to temporary rivers (TRs). We propose a new classification for TRs to better assess their ecological status. It arises from the LIFE+ TRivers project, which was conducted in the Catalan and the Júcar Mediterranean river basin districts (RBD). The European Water Framework Directive (WFD) provided two systems to set river types (systems A or B from Annex II), which have been officially used by water authorities across Europe to set “national river types” (NRTs). However, essential hydrological variables for TRs are largely omitted. NRTs established according to the WFD were compared with TR categories obtained by using a rainfall-runoff model, “natural flows prescribed regimes” (NFPRs), and with “aquatic phases regimes” (APRs) calculated by using TREHS software. The biological quality indices currently used in Spain, based on macroinvertebrates and diatoms (IBMWP, IMMI-T, and IPS), were compared with a “general degradation” gradient in order to analyze the two TR river classification procedures (NFPR and APR). The results showed that NRTs did not properly classify TRs, and that the APR classification identified ecologically meaningful categories, especially those related to stagnant phases. Four “management temporary river categories” based on APRs are proposed to be used for water managers to properly assess the ecological status of TRs., This research is based on TRivers LIFE + Project outcomes (LIFE13 ENV/ES/000341). The Catalan and Júcar RBDs provided funds for monitoring and data treatment.

Temporary rivers, characterized by shifts between flowing water, disconnected pools and dry periods, represent over 50% of the world’s river network and future climatic projections suggest their increase. These rivers are understudied, especially when only disconnected pools remain, because gauging stations or hydrological models do not inform of what happens after the cessation of flow. In addition, most of biological indicators for water quality are designed for flowing waters and their adequacy for temporary rivers is uncertain.The development of biological metrics adequate for the assessment of disconnected pools is difficult, because the high species replacement during and following flow cessation. For this reason, one hydrological variable of paramount importance for the assessment of ecological quality of disconected pools is the time since disconnection from the river flow.The objective of our work is to present a methodology to estimate the time since disconnection of pools from the river flow. This methodology, following the Gonfiantini (1986) model, is based on the sampling of water stable isotopes in disconnected pools. For pools disconnected from the groundwater, knowing the isotopic modification of the water in time due to evaporation, allows to estimate the relative volume of water evaporated since the pool has been disconnected. However, this approach gets complicated when pools have relevant rainfall inputs or exchanges with groundwater.Within the Vallcebre research area (42º12’N and 1º49’E), two artificial pools, one covered with a transparent lid to prevent the input of rainfall and another uncovered, were installed to validate this methodology in controlled conditions. From July to November 2020, water volume of these pools were weekly measured and sampled for isotopic analysis. In parallel, meteorological variables were monitored and rainfall was also sampled for water stable isotopes.To develop and validate an operational methodology for estimating the time since disconnection, we first calculated the relative amount of evaporated water based on the variations of isotopic composition of the covered pool samples, and estimated the time since disconnection (for a given natural pool) using the potential evaporation calculated from the meteorological data. For the uncovered pool, the information of amount and isotopic composition of rainfall was added in a mass balance model. Additionally, the same estimations were calculated with standard information (i.e. the meteorological data obtained from the National Meteorological Service and precipitation isotopes data from the Global Network of Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency). Finally, measured volumes changes in pools, were used to assess the limitations of the operational methodology and the sensitivity of the results to meteorological conditions.Our approach suggests that changes in isotopic composition can be a reliable method to estimate time since disconnection of pools in temporary rivers to better assess their ecological quality.

Fil: Epele, Luis Beltrán. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CONICET-UNPSJB), Esquel, Chubut, Argentina 2Facultad de Ciencias Naturales y Ciencias de la Salud, UNPSJB, Esquel, Chubut, Argentina 3Freshwater Ecology, Hydrology and Management group (FEHM), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain Fil: Dos Santos Daniel Andrés. Instituto de Biodiversidad Neotropical, CONICET –UNT, Cúpulas Universitarias S/N, Cátedra de Biología Animal, Facultad de Ciencias Naturales e IML, UNT, Yerba Buena, Tucumán, Argentina Fil: Sarremejane, Romain. INRAE, UR-RiverLy, Centre de Lyon-Grenoble Auvergne-Rhône- Alpes, Villeurbanne Cedex, France Fil: Grech, Marta Gladys. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CONICET-UNPSJB), Esquel, Chubut, Argentina 2Facultad de Ciencias Naturales y Ciencias de la Salud, UNPSJB, Esquel, Chubut, Argentina Fil: Macchi, Pablo Antonio. Universidad Nacional de Río Negro, Instituto de Investigación en Paleobiología y Geología, Río Negro, Argentina Fil: Manzo, Luz María. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CONICET-UNPSJB), Esquel, Chubut, Argentina Fil: MIserendino, María Laura. Centro de Investigación Esquel de Montaña y Estepa Patagónica (CONICET-UNPSJB), Esquel, Chubut, Argentina 2Facultad de Ciencias Naturales y Ciencias de la Salud, UNPSJB, Esquel, Chubut, Argentina Fil: Bonada, Núria. Freshwater Ecology, Hydrology and Management group (FEHM), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain Fil: Cañedo-Argüelles, Miguel. Serra-Hunter fellow, Freshwater Ecology, Hydrology and Management group (FEHM), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona, Barcelona, Spain Aim: To assess the relative importance of wind intensity and direction in explaining wetland invertebrate metacommunity organization. Location: Seventy-eight wetland ponds in Patagonia (Argentina) covering a study area of 3.5 × 10 5 km 2 . Time period: Ponds were sampled once between 2006 and 2014. Major taxa studied: One hundred and fifty-eight taxa of wetland aquatic invertebrates. Methods: We generated two beta diversity matrices (based on flying and non-flying invertebrates) and six predictor matrices, including three environmental distance matrices, a topographic distance between ponds, and two wind pairwise matrices differing in wind speed. Using Moran spectral randomization of Mantel (MSR-Mantel) tests (which account for spatial autocorrelation), we assessed the relationship between the response and the predictor matrices. We used a network-constrained version of the nestedness metric based on overlap and decreasing fill (NODF), to assess if wind anisotropy (i.e., direction-dependent) affected community nestedness among ponds. Results: Flying dispersers’ dissimilarity was significantly explained by environmental variables, whereas non-flying invertebrates’ dissimilarity was not significantly explained by any of the distances tested. When wind direction was ignored, wind speed had a negligible effect on both types of communities, whereas when it was considered a consistent nested pattern emerged, with the eastern ponds (downwind) communities being subsets of those from the western ponds (upwind). Aim: To assess the relative importance of wind intensity and direction in explaining wetland invertebrate metacommunity organization. Location: Seventy-eight wetland ponds in Patagonia (Argentina) covering a study area of 3.5 × 10 5 km 2 . Time period: Ponds were sampled once between 2006 and 2014. Major taxa studied: One hundred and fifty-eight taxa of wetland aquatic invertebrates. Methods: We generated two beta diversity matrices (based on flying and non-flying invertebrates) and six predictor matrices, including three environmental distance matrices, a topographic distance between ponds, and two wind pairwise matrices differing in wind speed. Using Moran spectral randomization of Mantel (MSR-Mantel) tests (which account for spatial autocorrelation), we assessed the relationship between the response and the predictor matrices. We used a network-constrained version of the nestedness metric based on overlap and decreasing fill (NODF), to assess if wind anisotropy (i.e., direction-dependent) affected community nestedness among ponds. Results: Flying dispersers’ dissimilarity was significantly explained by environmental variables, whereas non-flying invertebrates’ dissimilarity was not significantly explained by any of the distances tested. When wind direction was ignored, wind speed had a negligible effect on both types of communities, whereas when it was considered a consistent nested pattern emerged, with the eastern ponds (downwind) communities being subsets of those from the western ponds (upwind).

53 pages, 10 figures, 20 tables, This paper provides an overview of the last 40 years of use, and in many cases abuse, of the natural resources in Catalonia, a country that is representative of European countries in general, and especially those in the Mediterranean region. It analyses the use of natural resources made by mining, agriculture, livestock, logging, fishing, nature tourism, and energy production and consumption. This use results in an ecological footprint, i.e., the productive land and sea surface required to generate the consumed resources and absorb the resulting waste, which is about seven times the amount available, a very high number but very similar to other European countries. This overexploitation of natural resources has a huge impact on land and its different forms of cover, air, and water. For the last 25 years, forests and urban areas have each gained almost 3% more of the territory at the expense of agricultural land; those municipalities bordering the sea have increased their number of inhabitants and activity, and although they only occupy 6.7% of the total surface area, they account for 43.3% of the population; air quality has stabilized since the turn of the century, and there has been some improvement in the state of aquatic ecosystems, but still only 36% are in good condition, while the remainder have suffered morphological changes and different forms of nonpoint source pollution; meanwhile the biodiversity of flora and fauna remains still under threat. Environmental policies do not go far enough so there is a need for revision of the legislation related to environmental impact and the protection of natural areas, flora, and fauna. The promotion of environmental research must be accompanied by environmental education to foster a society which is more knowledgeable, has more control and influence over the decisions that deeply affect it. Indeed, nature conservation goes hand in hand with other social and economic challenges that require a more sustainable vision. Today’s problems with nature derive from the current economic model, which is environmentally unsustainable in that it does not take into account environmental impacts. Lastly, we propose a series of reasonable and feasible priority measures and actions related to each use made of the country’s natural resources, to the impacts they have had, and to their management, in the hope that these can contribute to improving the conservation and management of the environment and biodiversity and move towards sustainability, This research was funded by the Institut d’Estudis Catalans (IEC). With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

1. Rivers are dynamic ecosystems in which both human impacts and climate-driven drying events are increasingly common. These anthropogenic and natural stressors interact to influence the biodiversity and functioning of river ecosystems. Disentangling ecological responses to these interacting stressors is necessary to guide management actions that support ecosystems adapting to global change. 2. We analysed the independent and interactive effects of human impacts and natural drying on aquatic invertebrate communities—a key biotic group used to assess the health of European freshwaters. We calculated biological response metrics representing communities from 406 rivers in eight European countries: taxonomic richness, functional richness and redundancy, and biomonitoring indices that indicate ecological status. We analysed metrics based on the whole community and on a group of taxa with traits promoting resistance and/or resilience (‘high RR’) to drying. We also examined how responses vary across Europe in relation to climatic aridity. 3. Most community metrics decreased independently in response to impacts and drying. A richness-independent biomonitoring index (the average score per taxon; ASPT) showed particular potential for use in biomonitoring, and should be considered alongside new metrics representing high RR diversity, to promote accurate assessment of ecological status. 4. High RR taxonomic richness responded only to impacts, not drying. However, these predictors explained little variance in richness and other high RR metrics, potentially due to low taxonomic richness. Metric responsiveness could thus be enhanced by developing region-specific high RR groups comprising sufficient taxa with sufficiently variable impact sensitivities to indicate ecological status. 5. Synthesis and applications. Metrics are needed to assess the ecological status of dynamic river ecosystems—including those that sometimes dry—and thus to identify priority sites requiring action to tackle the causes of environmental degradation. Our results inform recommendations guiding the development of such metrics. We propose concurrent use of richness-independent ‘average score per taxon’ indices and metrics that characterize the richness of resistant and resilient taxa. We observed interactions between aridity, impacts and drying, highlighting that these new metrics should be region specific, river type specific and adaptable, promoting their ability to inform management actions that protect biodiversity in river ecosystems responding to climate change. European Cooperation in Science and Technology. Grant Number: CA15113

The study was supported by the COST Action CA15113 Science and Management of Intermittent Rivers and Ephemeral Streams (http://www.smires.eu), funded by COST (European Cooperation in Science and Technology). NC was supported by the French research program Make Our Planet Great Again. MC-A was supported by the MECODISPER project (CTM2017-89295-P) funded by the Spanish Ministerio de Economia, Industria y Competitividad (MINECO) - Agencia Estatal de Investigacion (AEI) and cofunded by the European Regional Development Fund (ERDF). AC-R acknowledges funding by MINECO-AEI-ERDF (CGL2014-53140-P). CG-C was supported by the EDRF (COMPETE2020 and PT2020) and the Portuguese Foundation for Science and Technology, through the CBMA strategic program UID/BIA/04050/2019 (POCI-01-0145-FEDER-007569) and the STREAMECO project (Biodiversity and ecosystem functioning under climate change: from the gene to the stream, PTDC/CTA-AMB/31245/2017). JH was supported by the project 'Global taxonomic, functional and phylogenetic diversity of stream macroinvertebrate communities: unravelling spatial trends, ecological determinants and anthropogenic threats' funded by the Academy of Finland. PP and MP were supported by the Czech Science Foundation (P505-20-17305S). ZC was supported by the projects EFOP-3.6.1.-16-2016-00004, 20765-3/2018/FEKUTSTRAT and TUDFO/47138/2019-ITM. We thank two anonymous reviewers for insightful feedback that improved an earlier draft of this manuscript., Dispersal is an essential process in population and community dynamics, but is difficult to measure in the field. In freshwater ecosystems, information on biological traits related to organisms’ morphology, life history and behaviour provides useful dispersal proxies, but information remains scattered or unpublished for many taxa. We compiled information on multiple dispersal-related biological traits of European aquatic macroinvertebrates in a unique resource, the DISPERSE database. DISPERSE includes nine dispersal-related traits subdivided into 39 trait categories for 480 taxa, including Annelida, Mollusca, Platyhelminthes, and Arthropoda such as Crustacea and Insecta, generally at the genus level. Information within DISPERSE can be used to address fundamental research questions in metapopulation ecology, metacommunity ecology, macroecology and evolutionary ecology. Information on dispersal proxies can be applied to improve predictions of ecological responses to global change, and to inform improvements to biomonitoring, conservation and management strategies. The diverse sources used in DISPERSE complement existing trait databases by providing new information on dispersal traits, most of which would not otherwise be accessible to the scientific community., COST Action Science and Management of Intermittent Rivers and Ephemeral Streams - COST (European Cooperation in Science and Technology) CA15113, French research program Make Our Planet Great Again, MECODISPER project - Spanish Ministerio de Economia, Industria y Competitividad (MINECO) - Agencia Estatal de Investigacion (AEI) CTM2017-89295-P, European Union (EU), MINECO-AEI-ERDF CGL2014-53140-P, EDRF (COMPETE2020), Portuguese Foundation for Science and Technology, through the CBMA strategic program UID/BIA/04050/2019 (POCI-01-0145-FEDER-007569), STREAMECO project (Biodiversity and ecosystem functioning under climate change: from the gene to the stream) PTDC/CTA-AMB/31245/2017, project 'Global taxonomic, functional and phylogenetic diversity of stream macroinvertebrate communities: unravelling spatial trends, ecological determinants and anthropogenic threats' - Academy of Finland, Grant Agency of the Czech Republic P505-20-17305S, EDRF (PT2020), EFOP-3.6.1.-16-2016-00004, 20765-3/2018/FEKUTSTRAT, TUDFO/47138/2019-ITM

Temporary rivers are characterized by shifting habitats between flowing, non-flowing and dry phases. Despite the fact that they are currently receiving significant attention by researchers and managers, the non-flowing (standing pools) phase has been largely disregarded. However, isolated pools in temporary rivers are transitional habitats of major ecological relevance as they can act as refuges for maintaining local and regional freshwater biodiversity. Factors such as pool duration and size, local physicochemical conditions, time since disconnection, distance to other freshwater habitats or presence of predators are crucial for a comprehensive understanding of the ecology of these habitats, and compromise to work towards adequate ecological quality assessments and conservation practices in temporary rivers.Research is ongoing focused on the development of a method for assessing the ecological status of disconnected pools, based on the relationship between the time elapsed after the pool disconnection and the characteristics of the biological communities taking into account the above-mentioned factors. The prevalence of the pool phase is assessed using the TREHS software tool through interviews with citizens as well as aerial and surface photographs examination. The time since disconnection is assessed with the help of low-cost sensors and water stable isotopes, whereas the local environmental characteristics are assessed using regular metrics. Finally, biological communities of the pools are characterized using both taxonomic and functional metrics, with the support of metabarcoding techniques, applied to diatoms, macrophytes, macroinvertebrates and fishes. This method aims to be used by water managers to improve the monitoring of the ecological status of temporary rivers, which are common around the world, harbor unique biodiversity and provide key ecosystem services.

The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; “CESTES”. Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology., Measurement(s)species abundance • species trait • environmental feature • latitude • longitudeTechnology Type(s)digital curationFactor Type(s)year of data collection • type of ecosystem • level of human disturbanceSample Characteristic - Environmentterrestrial natural environment • fresh water • marine biome • anthropogenic terrestrial biome • natural environment • area of mixed forest • cultivated environmentSample Characteristic - LocationEarth (planet) Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11317790

Motivation Dispersal is an essential process in population and community dynamics but is difficult to measure in the field. In freshwater systems, relevant information on the dispersal of many taxa remains scattered or unpublished, and biological traits related to organisms’ morphology, life history and behaviour offer useful dispersal proxies. We compiled information on selected dispersal-related biological traits of European aquatic macroinvertebrates in a unique source: the DISPERSE database. Information within DISPERSE can be used to address fundamental questions in metapopulation ecology, metacommunity ecology, macroecology, and eco-evolutionary research. From an applied perspective, the consideration of dispersal proxies can also improve predictions of ecological responses to global change, and contribute to more effective biomonitoring and conservation management strategies. Main types of variable contained Selected macroinvertebrate dispersal-related biological traits: maximum body size, adult female wing length, adult wing pair type, adult life span, number of reproductive cycles per year, lifelong fecundity, dispersal mode (i.e. active, passive, aquatic, aerial), and propensity to drift. Spatial location Europe. Time period Taxa considered are extant with recent records. Most data were collected in the 20th century and in the period 2000-2019. Major taxa and level of measurement Aquatic macroinvertebrates from riverine and lacustrine ecosystems, including Mollusca, Annelida, Platyhelminthes, and Arthropoda such as Crustacea and Insecta. For Insecta, aquatic stages and the aerial (i.e. flying) phases of adults were considered separately. Genus-level taxonomic resolution used, except for some Annelida and Diptera, which are coded at the sub-class, family or sub-family level. In total, the database includes 39 trait categories grouped into nine dispersal-related traits for 480 taxa. Software format The data file is in Excel workbook. BIOSKETCH Many of the authors are members of the European Cooperation in Science and Technology (COST) Action CA15113 Science and Management of Intermittent Rivers and Ephemeral Streams (SMIRES, www.smires.eu ), which aims to improve our understanding of intermittent rivers and ephemeral streams (IRES) and translate this into science-based, sustainable management of river networks. One of the main goals of SMIRES is to facilitate sharing of data and experience, bringing together researchers from many disciplines and stakeholders and creating synergies through networking. The dataset provided and analyzed herein reflects networking and collaboration within the SMIRES working group dedicated to Community Ecology and Biomonitoring.

The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; “CESTES”. Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology., This work was funded by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (funded by the German Research Foundation; DFG FZT 118). We thank Jitendra Gaikwad for his precious help with the technical aspects of the database storage and management through the iDiv Biodiversity Portal (https://idata.idiv.de/, https://doi.org/10.25829/idiv.286-21-2695) and the iDiv IT Support for their help in the CESTES website development (https://icestes.github.io/). The datasets provided by A. Jeliazkov were collected with financial support from the Fédération d’Ile-de-France pour la Recherche en Environnement (FIRE FR-3020). The dataset provided by R. Carvalho and F.L. Tejerina-Garro had financial support from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq No. 471283/2006-1) granted to FLTG. The datasets provided by R. van Klink, J.-Y. Humbert, R. Arlettaz and M.H.M. Menz were collected with financial support from the Swiss National Science Foundation (grants 31003A_125398/2 and 31003A_149656) awarded to RA.

When the regime of a river is not perennial, there are four main difficulties with the use of hydrographs for assessing hydrological alteration: i) the main hydrological features relevant for biological communities are not quantitative (discharges) but qualitative (phases such as flowing water, stagnant pools or lack of surface water), ii) stream flow records do not inform on the temporal occurrence of stagnant pools, iii) as most of the temporary streams are ungauged, their regime has to be evaluated by alternative methods such as remote sensing or citizen science, and iv) the biological quality assessment of the ecological status of a temporary stream must follow a sampling schedule and references adapted to the flow- pool-dry regime. To overcome these challenges within an operational approach, the freely available software tool TREHS has been developed within the EU LIFE TRIVERS project. This software permits the input of information from flow simulations obtained with any rainfall-runoff model (to set an unimpacted reference stream regime) and compares this with the information obtained from flow gauging records (if available) and interviews with local people, as well as instantaneous observations by individuals and interpretation of ground-level or aerial photographs. Up to six metrics defining the permanence of water flow, the presence of stagnant pools and their temporal patterns of occurrence are used to determine natural and observed river regimes and to assess the degree of hydrological alteration. A new regime classification specifically designed for temporary rivers was developed using the metrics that measure the relative permanence of the three main phases: flow, disconnected pools and dry stream bed. Finally, the software characterizes the differences between the natural and actual regimes, diagnoses the hydrological status (degree of hydrological alteration), assesses the significance and robustness of the diagnosis and recommends the best periods for biological quality samplings.

Aim Metacommunity assembly mechanisms have been traditionally considered stable through time. However, in highly dynamic systems with varying local environmental conditions and patch connectivity, communities are likely to experience temporal shifts in their assembly mechanisms. Here, we used a set of perennial (PR) and intermittent (IR) rivers to assess if assembly mechanisms vary seasonally in response to flow intermittence. Location Mediterranean climate region (100,000 km2), Spain. Methods We used a modelling approach to assess the relative effect of environmental sorting and dispersal-based processes on aquatic invertebrate metacommunities within and across river types at four distinct hydrological periods. We used local environmental variables to assess environmental sorting, and considered geographical, network and topographical distances as different dispersal surrogates. Linear mixed effect models accounting for the non-independence of pairwise distances were used to assess the relationships between community dissimilarity and distance matrices. Results Assembly mechanisms were more temporally stable in PR than in IR. In PR, community dissimilarities were equally related to environmental and geographical distances suggesting codominance of species sorting and dispersal-based assembly mechanisms. In IR, environmental distance best explained community dissimilarities during the dry period when flow cessation imposes strong environmental sorting, whereas metacommunity organization was much more stochastic during the rewetting period when high flows may randomly reorganize communities. Dispersal processes dominated assembly mechanisms between PR and IR during the rewetting period suggesting an increase in recolonization processes linking both river types following the dry period. Geographical and topographical distances best explained community variability, suggesting that overland dispersal dominates in river networks fragmented by drying events. Main conclusions Aquatic invertebrate metacommunity assembly mechanisms vary seasonally in response to changes in hydrological conditions. The temporal dimension should be better incorporated into metacommunity studies in highly dynamic systems such as intermittent rivers.

Comprehensive knowledge of the effects of disturbances on biodiversity is crucial for conservation and management, not least because ecosystems with low biodiversity may be the most vulnerable. In rivers, the role of disturbance in shaping aquatic biodiversity has mainly focused on floods. Perennial rivers (PRs) often flood, whereas intermittent rivers (IRs) flood, stop flowing and dry. Despite the recent and significant increase in research on IRs, controversy remains about whether they are more or less biodiverse than PRs. Our aim was to determine (Q1) if PRs and IRs differ in biodiversity and (Q2) if the direction and magnitude of the differences (effect sizes) are related to environmental (climate, season, habitat, longitudinal zonation and anthropogenic disturbance) and/or biological factors (taxonomic group). We conducted a meta-analysis on 44 published studies of PR and IR biodiversity that had replicated data. We applied random effects models to the data to obtain weighted mean effect sizes for differences between PRs and IRs, and their confidence intervals, by first considering all studies and then by splitting studies into groups on the basis of the above factors. We found that biodiversity was significantly higher in PRs than in IRs (Q1). We also detected significant differences (PRs> IRs) in studies of macroinvertebrates, in those conducted within arid and temperate climates, dry and wet sampling seasons, headwaters, and regions subject to different levels of anthropogenic disturbance (Q2). Our meta-analysis suggests that the expected increase in the prevalence of IRs in certain regions of the world due to global change could result in a decrease in freshwater biodiversity. To better manage and preserve aquatic biodiversity under future global change scenarios and to avoid potential ecosystem consequences of biodiversity loss, conservation efforts should be targeted towards those environmental conditions or taxonomic groups with significant differences (PRs > IRs).

Metacommunity studies commonly use spatial distances or, more recently, landscape resistance measures between study sites as a surrogate for connectivity. However, local communities are connected to many other sources of colonisation than the sites included in a study, and the availability and distance to potential colonisation sources may be better surrogates for dispersal than distances to other sampling sites. Here we test the effect of habitat connectivity on the assembly of stream-riffle macroinvertebrates with different dispersal abilities, after controlling for habitat heterogeneity and among-site distances (62 km on average). We used a null model approach to compare observed community dissimilarity to random expectation. Significant deviations from randomness were expected due to the hierarchical structure of river networks with their increasing flux of organisms from headwaters to mainstem reaches. We found a gradual shift in dispersal-based processes driving assembly mechanisms, from dispersal limitation in the isolated headwater streams to randomness in connected headwater and isolated mid-order streams, and to mass effects in the most connected mid-order streams. Weak flyers were constrained by dispersal limitation in the most isolated sites, whereas strong flyers were not restricted by the river network structure and were mainly assembled through mass effects. The approach taken was sufficient to unravel the importance of dispersal and habitat connectivity on community assembly and may therefore be particularly well suited to other large data sets with isolated sites (i.e. low geographical density of sites).

International audience; Non-perennial rivers and streams (NPRS) cover > 50% of the global river network. They are particularly predominant in Mediterranean Europe as a result of dry climate conditions, climate change and land use development. Historically, both scientists and policy makers underestimated the importance of NRPS for nature and humans alike, mainly because they have been considered as systems of low ecological and economic value. During the past decades, diminishing water resources have increased the spatial and temporal extent of artificial NPRS as well as their exposure to multiple stressors, which threatening their ecological integrity, biodiversity and ecosystem services. In this paper, we provide a comprehensive overview of the structural and functional characteristics of NPRS in the European Mediterranean, and discuss gaps and problems in their management, concerning their typology, ecological assessment, legislative and policy protection, and incorporation in River Basin Management Plans. Because NPRS comprise highly unstable ecosystems, with strong and often unpredictable temporal and spatial variability - at least as far as it is possible to assess - we outline the future research needs required to better understand, manage and conserve them as highly valuable and sensitive ecosystems. Efficient collaborative activities among multidisciplinary research groups aiming to create innovative knowledge, water managers and policy makers are urgently needed in order to establish an appropriate methodological and legislative background. The incorporation of NPRS in EU-Med River Basin Management Plans in combination with the application of ecological flows is a first step towards enhancing NPRS management and conservation in order to effectively safeguard these highly valuable albeit threatened ecosystems

Ecosystems experience natural disturbances and anthropogenic impacts that affect biological communities and ecological processes. When natural disturbance modifies anthropogenic impacts, current widely used bioassessment metrics can prevent accurate assessment of biological quality. Our aim was to assess the ability of biomonitoring metrics to detect anthropogenic impacts at both perennial and intermittent sites, and in the latter including both flowing and disconnected pool aquatic phases. Specifically, aquatic macroinvertebrates from 20 rivers were sampled along gradients of natural flow intermittence (natural disturbance) and anthropogenic impacts to investigate their combined effects on widely used river biomonitoring metrics (i.e. taxonomic richness and standard biological indices) and novel functional metrics, including functional redundancy (i.e. the number of taxa contributing similarly to an ecosystem function, here a trophic function) and response diversity (i.e. how functionally similar taxa respond to natural disturbance and anthropogenic impacts). Only the widely used IBMWP index (Iberian Biological Monitoring Working Party) was able to detect anthropogenic impacts in intermittent rivers when used during flowing phases. Several functional metrics also detected anthropogenic impacts regardless of flow intermittence. Besides, functional redundancy of the entire community remained effective even in disconnected pools. Synthesis and applications . Our results show that natural flow intermittence can confound river bioassessment, and that a set of new functional metrics could be used as effective alternatives to standard metrics in naturally disturbed intermittent rivers. Our findings suggest that water managers should incorporate alternative functional metrics in the routine biomonitoring of naturally disturbed rivers., The study was supported by the LIFE+ TRivers (LIFE13 ENV/ES/000341) project. We acknowledge the contribution of FEHM lab members and students who participated in fieldwork. C.G.‐C. was supported by a “Juan de la Cierva‐Formación” research contract (MINECO, FJCI‐2015‐25785). We especially thank Rachel Stubbington for her supervision and useful suggestions that greatly improved the manuscript.