Molluscs are the proverbial examples of slow movement. In this review, dispersal distances and speed were assessed from literature data. Active upstream movement can occur both individually and in ...groups; and depends on traits such as size, sex and reproductive status, and on external factors such as flow velocity, temperature, sediment structure, and food availability. The potential for active dispersal follows the sequence Pulmonata ≥ Prosobranchia > Bivalvia, although data for Pulmonata originated from short-term experiments that likely overestimated dispersal capabilities. Active upstream movement may be 0.3 to 1.0 km per year for most snails and is probably well below 0.1 km per year for bivalves. Natural passive upstream dispersal increases the range 10-fold (snails) to 100-fold (bivalves), and anthropogenic vectors can increase upstream dispersal more than 100-fold (snails) to 1000-fold (bivalves). Three km seems to be the maximal within-stream distance at which many species display regular population mixing, and at which re-colonisation or successful restoration can be expected within 3–10 years. Lateral dispersal between unconnected water bodies is passive and mostly known from observational reports, but potential distances depend on vectors, climate and geomorphology. In general, active dispersal seems insufficient to furnish a compensatory mechanism, e.g., for the rate of projected climate change. We provide an overview on dispersal strategies in the light of applied issues. More rigorous field surveys and an integration of different approaches (such as mark-recapture, genetic) to quantify distances and probabilities of lateral dispersal are needed to predict species distributions across space and time.
Non‐native species introductions affect freshwater communities by changing community compositions, functional roles, trait occurrences and ecological niche spaces. Reconstructing such changes over ...long periods is difficult due to limited data availability. We collected information spanning 215 years on fish and selected macroinvertebrate groups (Mollusca and Crustacea) in the inner‐Florentine stretch of the Arno River (Italy) and associated water grid, to investigate temporal changes. We identified an almost complete turnover from native to non‐native fish (1800: 92% native; 2015: 94% non‐native species) and macroinvertebrate species (1800: 100% native; 2015: 70% non‐native species). Non‐native fish species were observed ~50 years earlier compared to macroinvertebrate species, indicating phased invasion processes. In contrast, α‐diversity of both communities increased significantly following a linear pattern. Separate analyses of changes in α‐diversities for native and non‐native species of both fish and macroinvertebrates were nonlinear. Functional richness and divergence of fish and macroinvertebrate communities decreased non‐significantly, as the loss of native species was compensated by non‐native species. Introductions of non‐native fish and macroinvertebrate species occurred outside the niche space of native species. Native and non‐native fish species exhibited greater overlap in niche space over time (62%–68%) and non‐native species eventually replaced native species. Native and non‐native macroinvertebrate niches overlapped to a lesser extent (15%–30%), with non‐natives occupying mostly unoccupied niche space. These temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in α‐diversity and species turnover. These changes are potentially driven by deteriorations in hydromorphology as indicated by alterations in trait modalities. Additionally, we identified that angling played a considerable role for fish introductions. Our results support previous findings that the community turnover from native to non‐native species can be facilitated by, for example, deteriorating environmental conditions and that variations in communities are multifaceted requiring more indicators than single metrics.
We investigated local temporal changes in fish and macroinvertebrates over a period of 215 years. We identified an almost complete turnover from native to non‐native species. Analyses of changes in α‐diversities for native and non‐native fish and macroinvertebrates were nonlinear. Native and non‐native fish species exhibited greater overlap in niche space over time. Temporal changes in niche spaces of both biotic groups are a direct response to the observed changes in α‐diversity and species turnover, potentially driven by deteriorations in hydromorphology. Our results indicate that the turnover from native to non‐native species is multifaceted, requiring more indicators than single metrics.
The majority of studies on the ecological success of river restoration show improved morphological conditions, but a poor response of the biota. Because most river restoration projects are costly, a ...debate has started on the meaningfulness of such investments. Yet only a few studies have investigated the societal dimension of river restoration projects in detail. Therefore, the main aim of this study is to shed light on the social aspects of river restoration. Our empirical study consisted of two parts: (1) an explorative study conducted with 32 residents encountered at three restored river sections in Germany and (2) standardized telephone interviews with 760 residents living in the vicinity of 10 different restored river sections in three federal states. The survey covered questions including which activities local residents carry out at restored river sections, how they judge the nature experience, and how they perceive (negative) effects and costs. The restored river sections are perceived positively by > 80% of the respondents describing the respective section as near-natural and beautiful. In the view of the survey participants, both the ecosystem and residents profit highly from the restoration measure (> 90%), while the agricultural sector is not rated as a high profiteer (36%, multiple answers were possible). In full awareness of the costs of restoration projects (approximately 400,000 Euros per river km), 70% of the interviewees regard further restoration projects as useful and only 6% as not useful. The results show that river restorations are of great value and are held in high esteem by the population. Moreover, the interviewees considered the investments made by the public or sponsors to be predominantly useful. These results are highly valuable for water managers and politicians as the societal relevance of river restoration might be a key factor in the ongoing public and political discussion about river restoration.
Although most stream restoration projects succeed in improving hydromorphological habitat quality, the ecological quality of the stream communities often remains unaffected. We hypothesize that this ...is because stream communities are largely determined by environmental properties at a larger-than-local spatial scale. Using benthic invertebrate community data as well as hydromorphological habitat quality data from 1087 stream sites, we investigated the role of local- (i.e. 100m reach) and regional-scale (i.e. 5km ring centered on each reach) stream hydromorphological habitat quality (LQ and RQ, respectively) on benthic invertebrate communities. The analyses showed that RQ had a greater individual effect on communities than LQ, but the effects of RQ and LQ interacted. Where RQ was either good or poor, communities were exclusively determined by RQ. Only in areas of intermediate RQ, LQ determined communities. Metacommunity analysis helped to explain these findings. Species pools in poor RQ areas were most depauperated, resulting in insufficient propagule pressure for species establishment even at high LQ (e.g. restored) sites. Conversely, higher alpha diversity and an indication of lower beta dispersion signals at mass effects occurring in high RQ areas. That is, abundant neighboring populations may help to maintain populations even at sites with low LQ. The strongest segregation in species co-occurrence was detected at intermediate RQ levels, suggesting that communities are structured to the highest degree by a habitat/environmental gradient. From these results, we conclude that when restoring riverine habitats at the reach scale, restoration projects situated in intermediate RQ settings will likely be the most successful in enhancing the naturalness of local communities. With a careful choice of sites for reach-scale restoration in settings of intermediate RQ and a strategy that aims to expand areas of high RQ, the success of reach-scale restoration in promoting the ecological quality of communities can be greatly improved.
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•Local- and regional scale habitat quality exert interactive effects on stream communities.•At high or low regional habitat quality, community quality was independent of local habitat quality.•Only in areas of intermediate regional habitat quality did communities respond to local habitat quality.•Metacommunity structure and processes are analyzed to explain these results.•Spatial prioritization strategies for stream restoration projects are derived.
Global change effects on biodiversity and human wellbeing call for improved long-term environmental data as a basis for science, policy and decision making, including increased interoperability, ...multifunctionality, and harmonization. Based on the example of two global initiatives, the International Long-Term Ecological Research (ILTER) network and the Group on Earth Observations Biodiversity Observation Network (GEO BON), we propose merging the frameworks behind these initiatives, namely ecosystem integrity and essential biodiversity variables, to serve as an improved guideline for future site-based long-term research and monitoring in terrestrial, freshwater and coastal ecosystems. We derive a list of specific recommendations of what and how to measure at a monitoring site and call for an integration of sites into co-located site networks across individual monitoring initiatives, and centered on ecosystems. This facilitates the generation of linked comprehensive ecosystem monitoring data, supports synergies in the use of costly infrastructures, fosters cross-initiative research and provides a template for collaboration beyond the ILTER and GEO BON communities.
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•Monitoring changes in biodiversity requires improved standards and frameworks.•We link the Ecosystem Integrity and Essential Biodiversity Variables frameworks.•We make recommendations for long-term monitoring variables and instrumentation.•Site-based long-term monitoring data will become more broadly applicable.•Co-located monitoring site networks will enable covering all recommended variables.
Habitat connectivity and dispersal interact to structure metacommunities, but few studies have examined these patterns jointly for organisms across the aquatic–terrestrial ecotone. We assessed ...metacommunity structure and beta diversity patterns of instream benthic invertebrates, riparian carabid beetles (Order: Coleoptera; Family: Carabidae) and riparian spiders (Order: Araneae) at fifteen sites in a river‐floodplain system. Sampling took place over a three‐year period (2010–2012) in the Rhine‐Main‐Observatory LTER site on the Kinzig River, central Germany. This allowed disentangling the combined influence, and temporal variability, of habitat connectivity (i.e. between aquatic and terrestrial) and dispersal ability (i.e. between spiders and beetles, and aerial and aquatic dispersing invertebrates) on the dominant paradigms structuring these metacommunities. We found mostly consistent differences in the manner that metacommunities were structured between groups, with lower levels of variability explained for beetles compared to the other groups. Beetles were consistently structured more by turnover than nestedness components, with greater beta diversity than expected by chance and a minor spatial compared to environmental signal emerging with variance partitioning. Conversely, spiders and benthic invertebrates had lower beta diversity and greater nestedness than null expectation, and a clearer spatial signal controlling metacommunity structure. Our results suggest varying levels of mass effects and species sorting shape river‐floodplain metacommunities, depending on habitat connectivity and dispersal ability. That is, greater connectivity and lower fragmentation along the river compared to the terrestrial zone promoted mass effects, and differences in overall dispersal ability and mode (i.e. active and passive) for instream and riparian communities shifted paradigms between mass effects and species sorting.
Summary
1. Freshwater ecosystems will be profoundly affected by global climate change, especially those in mountainous areas, which are known to be particularly vulnerable to warming temperatures. We ...modelled impacts of climate change on the distribution ranges of 38 species of benthic stream macroinvertebrates from nine macroinvertebrate orders covering all river zones from the headwaters to large river reaches.
2. Species altitudinal shifts as well as range changes up to the year 2080 were simulated using the A2a and B2a Intergovernmental Panel on Climate Change climate‐warming scenarios. Presence‐only species distribution models were constructed for a stream network in Germany’s lower mountain ranges by means of consensus projections of four algorithms, as implemented in the BIOMOD package in R (GLM, GAM, GBM and ANN).
3. Species were predicted to shift an average of 122 and 83 m up in altitude along the river continuum by the year 2080 under the A2a and B2a climate‐warming scenarios, respectively. No correlation between altitudinal shifts and mean annual air temperature of species’ occurrence could be detected.
4. Depending on the climate‐warming scenario, most or all (97% for A2a and 100% for B2a) of the macroinvertebrate species investigated were predicted to survive under climate change in the study area. Ranges were predicted to contract for species that currently occur in streams with low annual mean air temperatures but expand for species that inhabit rivers where air temperatures are higher.
5. Our models predict that novel climate conditions will reorganise species composition and community structure along the river continuum. Possible effects are discussed, including significant reductions in population size of headwater species, eventually leading to a loss of genetic diversity. A shift in river species composition is likely to enhance the establishment of non‐native macroinvertebrates in the lower reaches of the river continuum.
The challenges posed by climate and land use change are increasingly complex, with ever-increasing and accelerating impacts on the global environmental system. The establishment of an internationally ...harmonized, integrated, and long-term operated environmental monitoring infrastructure is one of the major challenges of modern environmental research. Increased efforts are currently being made in Europe to establish such a harmonized pan-European observation infrastructure, and the European network of Long-Term Ecological Research sites – LTER-Europe – is of particular importance. By evaluating 477 formally accredited LTER-Europe sites, this study gives an overview of the current distribution of these infrastructures and the present condition of long-term environmental research in Europe. We compiled information on long-term biotic and abiotic observations and measurements and examined the representativeness in terms of continental biogeographical and socio-ecological gradients. The results were used to identify gaps in both measurements and coverage of the aforementioned gradients. Furthermore, an overview of the current state of the LTER-Europe observation strategies is given. The latter forms the basis for investigating the comparability of existing LTER-Europe monitoring concepts both in terms of observational design as well as in terms of the scope of the environmental compartments, variables and properties covered.
•First study on conceptual and infrastructural comparability of LTER-Europe•Analysis of biogeographical and socio-ecological representativeness of LTER-Europe•Classification of LTER Europe sites based on the LTER framework of standard observations
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Long-term observations on riverine benthic invertebrate communities enable assessments of the potential impacts of global change on stream ecosystems. Besides increasing average temperatures, many ...studies predict greater temperature extremes and intense precipitation events as a consequence of climate change. In this study we examined long-term observation data (10–32years) of 26 streams and rivers from four ecoregions in the European Long-Term Ecological Research (LTER) network, to investigate invertebrate community responses to changing climatic conditions. We used functional trait and multi-taxonomic analyses and combined examinations of general long-term changes in communities with detailed analyses of the impact of different climatic drivers (i.e., various temperature and precipitation variables) by focusing on the response of communities to climatic conditions of the previous year. Taxa and ecoregions differed substantially in their response to climate change conditions. We did not observe any trend of changes in total taxonomic richness or overall abundance over time or with increasing temperatures, which reflects a compensatory turnover in the composition of communities; sensitive Plecoptera decreased in response to warmer years and Ephemeroptera increased in northern regions. Invasive species increased with an increasing number of extreme days which also caused an apparent upstream community movement. The observed changes in functional feeding group diversity indicate that climate change may be associated with changes in trophic interactions within aquatic food webs. These findings highlight the vulnerability of riverine ecosystems to climate change and emphasize the need to further explore the interactive effects of climate change variables with other local stressors to develop appropriate conservation measures.
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•We examined the effects of climate change on benthic invertebrate communities.•Stronger effects of previous year climatic conditions than gradual changes over time•No changes in overall abundance and number of taxa, but taxon-specific changes•Stronger impact of temperature on sensitive taxa in agricultural regions•Changing climatic conditions associated with changes in feeding group composition
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