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Abstract

There is an urgent need to track how natural systems are responding to global change in order to better guide management efforts. Traditionally, taxonomically based metrics have been used as indicators of ecosystem integrity and conservation status. However, functional approaches offer promising advantages that can improve bioassessment performance. In this study, we aim to test the applicability of functional redundancy (FR), a functional feature related to the stability, resistance and resilience of ecosystems, as a tool for bioassessment, looking at woody riparian communities in particular. We used linear mixed-effect models to investigate the response of FR and other traditional biomonitoring indices to natural (drought duration) and anthropogenic stress gradients (flow regulation and agriculture) in a Mediterranean basin. Such indices include species richness, a taxonomic index, and the Riparian Quality Index, which is an index of ecological status. Then, we explored the ability of FR and the other indices to discriminate between different intensities of human alteration. FR showed higher explanatory capacity in response to multiple stressors, although we found significant negative relationships between all the biological indices (taxonomic, functional and ecological quality) and stress gradients. In addition, FR was the most accurate index to discriminate among different categories of human alteration in both perennial and intermittent river reaches, which allowed us to set threshold values to identify undisturbed (reference condition), moderately disturbed and highly disturbed reaches in the two types of river. Using these thresholds and the best-fitting model, we generated a map of human impact on the functional redundancy of riparian communities for all the stretches of the river network. Our results demonstrate that FR presents clear advantages over traditional methods, which suggests that it should be part of the biomonitoring toolbox used for environmental management so as to obtain better predictions of ecosystem response to environmental changes.

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... Species-level characterization of the terrestrial and semi-aquatic plant assemblages that establish in dry channels is needed to inform their use in dry-phase biomonitoring. Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
Technical Report
Full-text available
Intermittent rivers and Ephemeral Streams (IRES) are river water bodies characterised by temporary flow. They are widespread across the EU and a significant proportion of them is expected to increase due to climate change scenarios and rising water demands. The purpose of this handbook is to help water managers to understand the natural processes prevailing in IRES and their importance for biodiversity and local communities in order to better manage them. Since it is widely accepted that these types of systems have been up until recently neglected, the transfer of knowledge from scientists to water managers is required for their proper ecological status assessment, and crucial for their protection and restoration. Therefore, this SMIRES handbook will also bring about a better understanding of IRES, and will provide for the provision of tools needed for managing them in the best possible way. Eight case studies, located in different countries, aim at illustrating different experiments of managing IRES where the knowledge previously presented in the handbook is needed and used. These experiments do not claim to be exemplary practices to be reproduced everywhere but instead give insights of what could be done, what should be strengthened and what should be avoided in specific contexts. The issues are various: restoration of habitats, reduction of erosion, flood prevention, mitigation of hydrological drought, raise of groundwater levels, etc. Among the lessons learned, all case studies insist on the importance of increasing people awareness about the ecosystem services associated with IRES and encourage local stakeholders to involve themselves in restoration projects of IRES. A specific attention to project monitoring is also pointed out to assess the outputs and to encourage other initiatives to be taken.
... Estas herramientas realizan dicha evaluación mediante la comparación de hidrogramas impactados con los de referencia (correspondientes al régimen hidrológico natural) (Gallart et al., 2016). Esta metodología se aplica en métodos como IHA (Indicators of Hydrologic Alteration; Richter et al., 1996) Brown et al., 2013). ...
... El método IHARIS es una adaptación del IHA para España (Martínez Santa-María & Fernández Yuste, 2010), por lo que su funcionamiento es similar. Por otro lado, la herramienta DRIFT fue desarrollada para ríos de Sudáfrica y está basada en un enfoque interactivo y holístico para asesorar sobre los impactos en los flujos ambientales de los ríos (Brown et al., 2013). ...
... diversidad o redundancia funcional), que han demostrado tener gran potencial para discriminar entre múltiples tipos de estrés y también presentan ventajas sobre métricas basadas en la taxonomía (utilizadas hoy en día), por lo que algunos estudios recientes incentivan su uso para biomonitoreo (p.ej. Villéger et al. 2008;Gutiérrez-Cánovas et al. 2015;Bruno et al., 2016). De hecho, se ha observado que algunas métricas funcionales podrían ser universales, ya que responden de la misma manera tanto en ríos permanentes como en RTs (Soria et al., 2020). ...
... Anthropogenic flow regime alterations of natural flow regimes through water abstraction and dams involve changes in the intensity, frequency, and seasonal predictability of floods and droughts. These changes can subsequently alter organic matter and sediment transport (Dewson, James, & Death, 2007;Meador & Carlisle, 2012), with direct effects on riparian and aquatic biota, such as habitat homogenisation (Belmar, Bruno, Martínez-Capel, Barquín, & Velasco, 2013), changes in indicator taxa and ecological traits , reduced diversity (Bruno, Gutierrez-Cánovas, Velasco, & Sánchez-Fernandez, 2016;Lobera, Muñoz, López-Tarazón, Vericat, & Batalla, 2017), and network simplification (Tonkin, Merritt, Olden, Reynolds, & Lytle, 2018). The ubiquity of flow alteration has led to a recent great interest in understanding aquatic ecosystem response to various types and degrees of flow regime alteration (see reviews by Dewson et al., 2007;Poff & Zimmerman, 2010). ...
... In fact, both natural intermittence and flow regulation affect water quantity and quality, habitat availability, as well as lateral, longitudinal and vertical connectivity (Bond, Lake, & Arthington, 2008). These impacts can involve changes in aquatic communities (Mulholland, Marzolf, Webster, Hart, & Hendricks, 1997) and ecosystem functioning (Bruno, Gutierrez-Cánovas, Velasco, et al., 2016). ...
... Previous studies conducted in Mediterranean rivers have assessed functional changes in aquatic and riparian communities along natural gradients of water salinity and flow intermittence (Suárez et al., 2017), as well as along anthropogenic stress gradients such K E Y W O R D S biological traits, functional diversity, functional redundancy, hydrologic alteration, intermittent streams as agriculture or flow regime alteration (Bruno, Gutiérrez-Cánovas, Sánchez-Fernández, Velasco, & Nilsson, 2016;Bruno, Gutierrez-Cánovas, Velasco, et al., 2016;Gutiérrez-Cánovas et al., 2015;Mellado-Díaz, Suárez, & Vidal-Abarca, 2008). These studies found that functional diversity and redundancy measures decreased as environmental stress increased, regardless of whether the origin of such stress was natural or anthropogenic. ...
Article
1. Running waters in Mediterranean regions are strongly regulated by dams, which produce significant alterations to natural flow regimes. Climate change will reduce discharge and increase flow intermittence in Mediterranean streams, which will lead to an intensified flow regulation to meet water demands. Very little is known about how the functional features of aquatic communities vary along combined anthropogenic flow alteration and natural intermittence gradients. 2. As intermittent streams are subjected to natural stress (droughts and flash floods), the flow regime alteration effect may differ from that observed in perennial rivers. Consequently, studies that aim to determine the effects of flow regulation on the functioning of aquatic communities in a global change context are crucial. 3. By applying linear mixed-effect models and null models to the macroinvertebrate communities from 65 stream sites in the Segura River Basin (south-east Spain), we assessed the separate effects of natural flow intermittence and flow regulation, as well as their interaction, on biological traits and functional diversity indices. 4. Natural flow intermittence and flow regulation were mainly associated with loss of taxa with semivoltine or univoltine cycles and more sensitive aquatic stages (i.e. eggs), and with the replacement by taxa with multivoltine cycles and more resistant aquatic stages (i.e. adults). Flow regulation intensified the impact of natural flow intermittence on some biological traits, producing synergistic effects (i.e. decreasing interstitial taxa and tegument breathers and increasing taxa with aquatic adult stages). At the same time, antagonistic (life cycle) and opposing (shredders) interaction effects were also observed. Functional diversity, functional dispersion, and functional redundancy underwent a non-random decrease as the flow regime alteration increased, and a significant antagonistic interaction was also found between both stressors for functional redundancy. 5. In general, flow regulation effects were stronger in perennial than in intermittent streams because natural intermittence imposes a previous eco-evolutionary pressure on aquatic biota by selecting those resistant or recovery traits that confer resilience to anthropogenic flow regime alterations. Thus, the natural flow regime influences the functional sensibility of communities to anthropogenic flow alteration.
... 4.7.2 Riparian plant communities as biomonitors of Mediterranean IRES: a case study Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
... Species-level characterization of the terrestrial and semi-aquatic plant assemblages that establish in dry channels is needed to inform their use in dry-phase biomonitoring. Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
Technical Report
Full-text available
Chapter 3 of the Intermittent rivers and ephemeral streams: what water managers need to know. Technical report – Cost ACTION CA 15113
... Species-level characterization of the terrestrial and semi-aquatic plant assemblages that establish in dry channels is needed to inform their use in dry-phase biomonitoring. Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
... Species-level characterization of the terrestrial and semi-aquatic plant assemblages that establish in dry channels is needed to inform their use in dry-phase biomonitoring. Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
... Species-level characterization of the terrestrial and semi-aquatic plant assemblages that establish in dry channels is needed to inform their use in dry-phase biomonitoring. Bruno et al. (2016a) investigated the use of riparian vegetation as bioindicators in Mediterranean-climate perennial rivers and IRES using taxonomic and functional community metrics. Riparian species richness and quality (Riparian Quality Index, González del Tánago and García de Jalón, 2011) were reduced by land-use intensification, flow regulation and natural flow intermittence. ...
... 18;Bruno et al., 2016a). ...
... 18 Spatial patterns of human impact levels based on predicted values of the functional redundancy of riparian vegetation communities in IRES (thin lines) and perennial rivers (thick lines) in a basin in south-east Spain.Bruno et al. (2016a) provide further details.FromBruno et al. (2016a). ...
Chapter
Full-text available
In a nutshell: ▪ There is a variety of benefits that IRES provide to our societies, from the provision of materials such as water and timber, to iconic species, the regulation of biogeochemical cycles, and space for cultural manifestation and as a corridor for both wild and herded animals. ▪ Drying and rewetting processes, timing and duration of different aquatic phases, have an effect on the biodiversity and ecosystem functioning, as well as on the provision of ecosystem services and on the social perception of them. ▪ There are intrinsic and relational values associated to IRES that are not usually recognised, including sense of place, cultural identity, social cohesion or nature stewardship. ▪ There is a long list of indicators that can be used to assess the provision of ecosystem services, and different techniques of monetary and non-monetary methods can be applied to assess their value. ▪ Public participation is also necessary to understand the multiple values of IRES and to improve social perception. Participatory mapping, citizen science, and scenario planning are some of the methodologies can be employed.
... El método IHARIS es una adaptación del IHA para España (Martínez Santa-María & Fernández Yuste, 2010), por lo que su funcionamiento es similar. Por otro lado, la herramienta DRIFT fue desarrollada para ríos de Sudáfrica y está basada en un enfoque interactivo y holístico para asesorar sobre los impactos en los flujos ambientales de los ríos (Brown et al., 2013). ...
... correspondientes al régimen hidrológico natural) (Gallart et al., 2016). Esta metodología se aplica en métodos como IHA (Indicators of Hydrologic Alteration; Richter et al., 1996), IHARIS (Indicators of Hydrologic Alteration in RIverS; Martínez Santa-María & Fernández Yuste, 2010) o DRIFT (Downstream Response to Imposed Flow Transformations;Brown et al., 2013). ...
... diversidad o redundancia funcional), que han demostrado tener gran potencial para discriminar entre múltiples tipos de estrés y también presentan ventajas sobre métricas basadas en la taxonomía (utilizadas hoy en día), por lo que algunos estudios recientes incentivan su uso para biomonitoreo(p.ej. Villéger et al. 2008; Gutiérrez- Cánovas et al. 2015;Bruno et al., 2016). De hecho, se ha observado que algunas métricas funcionales podrían ser universales, ya que responden de la misma manera tanto en ríos permanentes como enRTs (Soria et al., 2020).Entre las métricas funcionales, la redundancia funcional (el número de especies contribuyendo de forma similar a una función del ecosistema) parece funcionar mejor que la diversidad funcional y, además, proporciona información sobre la estabilidad, resiliencia y resistencia de los ecosistemas(Rosenfeld, 2002; Hooper et al., 2005; Laliberté & Legendre 2010; Guillemot et al., 2011;Bruno et al., 2016). ...
... Recent applications have taken place in grasslands (Pakeman, 2011;de Bello et al., 2013;Catorci et al., 2014;Vandewalle et al., 2014;Rota et al., 2017), Mediterranean shrublands (de Frutos et al., 2015), arable fields and serpentine communities (Plaza et al., 2015;Carmona et al., 2017;Flinn et al., 2017), tundra (Spasojevic and Suding, 2012), and coastal plant communities (Castro-Díez et al., 2016). In the case of riparian woodlands, FR has been used as a tool for bioassessment (Bruno et al., 2016b), FRic, FEve and FDiv for environmental stress (Kotowski et al., 2010;Giehl and Jarenkow, 2015;de la Riva et al., 2016a), FDis for land use change (Brice et al., 2017), and FD for plant invasions (Dechoum et al., 2015). According to our search, the earliest published ISI paper on functional diversity of riparian forest assemblages dates from 1997 (Higgins et al., 1997). ...
... Functional Richness (FRic) appears to be the most widely used functional diversity index, mainly coupled with Functional Evenness (FEve) and Functional Divergence (FDiv) (Kotowski et al., 2010;Savage and Cavender-Bares, 2012;de la Riva et al., 2016a). A enhanced group of functional diversity indices (FRic, FEve, FDiv and Functional Dispersion (FDis) has been also used Hedberg et al., 2016), as have single functional diversity indices, such as FDis (Lawson et al., 2015b;Craven et al., 2016;Göthe et al., 2016;Brice et al., 2017), Functional Redundancy (FR) (Bruno et al., 2016b); and Rao (Q) (Sasaki et al., 2014). ...
... However, our understanding of ecological resilience is hampered by the lack of consistent measurement methods (Newton 2016, Baho et al. 2017, Pimm et al. 2019. A common framework for the evaluation of ecosystem resilience focuses on trait-based proxies of ecosystem functioning (Bruno et al. 2016, Gladstone-Gallagher et al. 2019). One of the most commonly used proxies of ecological resilience is functional redundancy (Gunderson 2000, Baho et al. 2017, Gladstone-Gallagher et al. 2019, due to its ease of interpretation and estimation. ...
... Functional redundancy (FR) quantifies the functional convergence of species within a community, based on traits (Walker 1992, Hubbell 2006, Bruno et al. 2016, Lamothe et al. 2018. Generally, high FR indicates that species within a community have relatively similar traits and consequently play similar roles, while low FR indicates that species traits and roles differ. ...
Article
Full-text available
Functional redundancy (FR) is commonly invoked as one of the main mechanisms underlying ecological resilience. However, little is known about the extension of FR from single to multiple functions and its variation among ecological assemblages at bio-geographic scales. We studied 51 assemblages of Eurasian small mammals (Mammalia: Rodentia and Mammalia: Soricomorpha), analyzing FR across and within assemblages. We quantified FR for trait sets related to five different functions: parasitic interactions, diet, habitat preferences, body mass and diel activity. We then evaluated the relationships between FR based on different functional trait sets across and within mammal assemblages, to determine whether small mammal assemblages and their species are redundant for single or multiple trait sets and thus, whether they are complementary or fully redundant when considering multiple functions. Further, we analyzed the influence of geography, climate, plant productivity and land use on FR. We found that FR based on mammal parasitic interactions, body mass and diel activity were positively correlated, whereas FR based on mammal body mass and habitat preferences were negatively related. These relationships were consistent across and within mammal assemblages. Additionally, FR mainly varied along geographic gradients (latitude and longitude). FR based on parasitic interactions, body mass and diel activity followed similar patterns, increasing at northern latitudes, possibly as a response to environmental filtering processes. FR for diet and habitat preferences increased at easterly longitudes, which may be due to landscape homogeneity in sites across central and eastern Asia. Despite redundancy across multiple functional trait sets, Eurasian small mammal assemblages were complementary when considering all five trait sets. Our results warn against conclusions drawn from the study of FR based on traits related to a single function.
... Numerous taxonomic metrics widely used in biomonitoring programmes and functional indices (functional richness and redundancy) were explored allowing us to go beyond a traditional taxonomic approach. Functional measures at the community level are related to ecosystem functioning and stability [21] and can reveal community responses to a variety of stressors [22,23]. Specifically, we aimed to study and test the different relevance of multiple stressors (hydrological, chemical, physical variability) on (i) community metrics and indices and (ii) community structure. ...
... The relevance of the functional approach has been already stressed in some biomonitoring indices (e.g., France, [35]) in which macroinvertebrate trait metrics are directly integrated. Moreover, functional redundancy has recently been proposed as a biomonitoring tool to monitor responses in the riparian vegetation [22] and tested on macroinvertebrate communities in a highly regulated Mediterranean basin [45]. ...
Article
Full-text available
Aquatic macroinvertebrates are frequently used to evaluate river system conditions and restoration project performance. A better understanding of macroinvertebrate community responses to multiple stressors is a primary challenge for river science. In this paper, macroinvertebrate responses to hydrological and water quality variability were studied in the regulated Oglio River (northern Italy). We hypothesized that in regulated rivers the hydrological, rather than the physico-chemical conditions, would affect macroinvertebrate communities and biomonitoring tools (taxonomic metrics and functional indices). Repeated sampling (six times a year) was performed at four sites downstream of four dams in a 30 km river stretch during 2014 and 2015. Data were analysed using a linear mixed effect framework, to take into account random variation due to site and sampling date, and with multivariate analysis to track changes in community structure. A total of 69 families and 134,693 organisms were identified. The investigated metrics were mainly affected by the coefficient of variation of discharge, minimum discharge, ammonium, and temperature. The short-term dynamics of hydrological and physico-chemical variables were generally less important than the overall random effects as drivers of macroinvertebrate-based metrics. However, the relevance of a random effect (site, time, their interaction) differed depending on the biological metrics analysed. Understanding potential differences in response to short term and short stretch conditions would benefit biomonitoring and restoration procedures in both regulated and natural rivers.
... We envisioned FD to be more resilient than TD to anthropogenic LUCC, albeit the high sensitivity of higher trophic level functional groups (e.g. predators) (Bruno, Gutiérrez-Cánovas, Velasco, & Sánchez-Fernández, 2016;Cadotte et al., 2011). Specifically, we address the following questions: (1) What is the relationship between GDB TD and FD in a disturbance gradient within a FL? (2) Is combining both approaches the best strategy to monitor disturbance and/or restoration of Neotropical forests? ...
Article
Changes in biodiversity and ecosystem services are usually evaluated using taxonomic indicators or, to a lesser extent, functional indicators. The present work adds new insights on the links between taxonomic indicators and functional indicators within a disturbance gradient in the Brazilian Amazon. Ground dwelling beetles’ functional groups were used to complement taxonomic diversity in indicating disturbance and/or ecosystem restoration. Significant correlations were found between taxonomic and functional indicators. Our results show that increasingly disturbed ecosystems are related with reductions in functional redundancy with probable detrimental effects on the future landscape resilience. Moreover, results highlight that even species‐rich Neotropical forest landscapes may be highly vulnerable to the removal of keystone diversity. Remarkably, secondary forests support equivalent functional diversity and, partially, taxonomic diversity to primary forests. Overall, disturbance indicators supported on complementary measures such as composition, species diversity and functionality were sensitive to the ecosystems’ gradient and could be used for assessing the extent of landscape change but also to guide restoration and management practices in Neotropical forest landscapes.
... This fact indicates that diversity-based indicators are inappropriate for evaluating saline watercourses, and are also potentially inaccurate for other naturally stressed systems (Cañedo-Argüelles et al., 2012;Elliott and Quintino, 2007). Previous studies have also demonstrated that conventional biomonitoring metrics show substantial limitations when evaluating the ecological quality of naturally stressed ecosystems, such as intermittent rivers (Bruno et al., 2016;Wilding et al., 2018) or estuaries (Elliott and Quintino, 2007). ...
Article
Naturally stressed ecosystems hold a unique fraction of biodiversity. However, they have been largely ignored in biomonitoring and conservation programmes, such as the EU Water Framework Directive, while global change pressures are threatening their singular values. Herewe present a framework to classify and evaluate the ecological quality of naturally stressed rivers along a water salinity gradient. We gathered datasets, including aquatic macroinvertebrate assemblages and environmental information, for 243 river locations across the western Mediterranean to: a) gauge the role of natural stressors (salinity) in driving aquatic community richness and composition; b) make river classifications by encompassing the wide range of environmental and biological variation exhibited by Mediterranean rivers; c) provide effective biomonitoring metrics of ecological quality for saline rivers. Our results showed that water salinity played a pivotal role in explaining the community richness and compositional changes in rivers, evenwhen considering other key and commonly used descriptors, such as elevation, climate or lithology. Both environmental and biologically-based classifications included seven river types: three types of freshwater perennial rivers, one freshwater intermittent river type and three new saline river types. These new saline types were not included in previous classifications. Their validation by independent datasets showed that the saline and freshwater river types represented differentiable macroinvertebrate assemblages at family and species levels. Biomonitoring metrics based on the abundance of indicator taxa of each saline river type provided amuch better assessment of the ecological quality of saline rivers than otherwidely used biological metrics and indices. Here we demonstrate that considering natural stressors, such aswater salinity, is essential to design effective and accurate biomonitoring programmes for rivers and to preserve their unique biodiversity.
... At the opposite, CCS (an experimental constructed and contaminated soil) with the lowest fertility level and the highest metal concentration of the study, harbored the highest taxonomic diversity but a low functional diversity of Collembola. This might suggest functional redundancy of species within the community, defined as several species contributing in equivalent ways to an ecosystem function such that one species may substitute for another (Bruno et al., 2016). Species that are functionally redundant act as 'spare wheels' during a disturbance to maintain ecosystem functions (Cole et al., 2006). ...
... Approaches for quantifying functional redundancy continue to be developed (de Bello, Lepš, Lavorel, & Moretti, 2007;Bruno, Gutiérrez-Cánovas, Velasco, & Sánchez-Fernández, 2016;van der Linden et al., 2012;Ricotta et al., 2016), but typically is approached from multiple scales and requires community abundance or presence-absence data with a matrix of morphological, behavioural or life-history traits (i.e., functional traits; Rosenfeld, 2002). Using these trait data, ordinations are commonly performed to develop multivariate functional trait spaces that allow subsequent measures of functional diversity to be calculated (e.g., functional richness; Villéger, Mason, & Mouillot, 2008). ...
Article
Aim: Functional redundancy occurs when species share overlapping ecological functions and is considered an important component of ecosystem resilience. However, much of what we know about functional redundancy comes from relatively species‐rich terrestrial and marine environments. Here, we examined patterns of functional redundancy among Ontario freshwater fish communities with species richness levels ranging from 4 to 30 species across lakes of differing size, depth, productivities and thermal characteristics. Location: Six thousand nine hundred and seventy‐seven lakes in Ontario, Canada. Methods: We examined functional redundancy by quantifying the relationship between functional diversity and species richness in lakes across Ontario and within smaller biogeographic regions. We used null models to test whether fish communities had greater redundancy than expected from random assemblages. We then used generalized additive models (GAMs) to predict how patterns of redundancy vary across environmental variables. At last, we compared species‐level functional rarity metrics across fish thermal preference groups, body sizes and species occurrence rates. Results: The functional diversity and species richness relationship were saturating among fish communities at the provincial scale but varied between smaller regions with differing biogeographic histories. Most communities fell within expectations from weighted null models of the functional diversity and species richness relationship. The GAMs indicated that fish communities in the largest, deepest and warmest lakes showed the greatest overall functional redundancy. No differences were observed in functional rarity measures between thermal preference groups, across body sizes or across species occurrence rates. Main conclusions: Although lakes in this study were relatively depauperate of fish species, Ontario fish communities exhibited functional redundancy at the provincial scale, with variation regionally. North‐eastern communities showed the least saturating relationship overall as predicted by historical biogeographic patterns of freshwater fish colonization. Overall, this study provides a broad perspective of freshwater fish diversity patterns and highlights the importance of investigating redundancy from different perspectives and multiple spatial scales.
... Approaches for quantifying functional redundancy continue to be developed (Bruno et al. 2016;Ricotta et al. 2016), but typically require community abundance or presence-absence data and a matrix of morphological, behavioral, or life-history traits (Rosenfeld 2002). Using these data, Interpretations of the functional diversity and species richness relationship can vary based on the types of traits used in the analysis. ...
Thesis
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As many as 2 million lakes are estimated to be in Canada that provide beneficial ecosystem services to society such as clean drinking water and freshwater fisheries. However, anthropogenic disturbances on the landscape threaten the delivery of these services and pose questions regarding the maintenance of lake systems to future change. Understanding and quantifying the resistance and resilience of lake systems to disturbance is therefore a priority. The objectives of this thesis are to: 1) develop a quantitative framework for characterizing the resistance and resilience of ecosystems to disturbance; and, 2) quantify the relative resistance and resilience of freshwater lakes in Ontario to anthropogenic disturbance. I begin with a simulation study to demonstrate how distance-based measures in ordination space can provide a framework for characterizing the relative resistance and resilience of systems to disturbance. I then apply the distance-based approach to long-term monitoring data of crustacean zooplankton communities and associated water chemistry data from 19 lakes in Ontario subjected to varying levels of acidification. I show that most zooplankton communities lack resistance to change over time, whether affected by acidification or not, and that water chemistry is changing among all the lakes studied. Finally, I approach resilience from a functional diversity perspective and quantify the functional redundancy of Ontario lake fish communities across the province and relate these iii patterns to biogeographic and environmental variables. My results demonstrate patterns of redundancy among freshwater fish communities provincially, however, these patterns varied regionally. Overall, this body of work provides a multidimensional approach for characterizing the resistance and resilience of freshwater ecosystems to anthropogenic disturbance that can be applied across systems (e.g. terrestrial, marine, freshwater) and scales (e.g., species, community, ecosystem).
... Furthermore, conservation efforts are usually focused on perennial systems to the detriment of intermittent and ephemeral ones, which occupy more than 50% of drainage networks globally (Datry et al. 2014). Given that intermittent and ephemeral systems have different natural disturbance regimes and support different species than perennial systems (Meyer et al. 2007), the management and evaluation of the ecological status of intermittent and ephemeral systems may require different ecological indices and thresholds (e.g., Bruno et al. 2016). Intermittent and ephemeral systems host a diversity of taxa that are usually adapted to high natural dynamism, potentially making them more resilient to climate change than taxa from perennial systems. ...
... Functional approaches can complement taxonomic community characterization by exploring the biological and ecological traits possessed by a sampled assemblage. Despite limitations of biological trait databases (Wilkes et al., 2017), measures of functional diversity can be reliable indicators of human impacts in perennial rivers (Charvet et al., 2000;Dolédec et al., 1999), and Bruno et al. (2016) found functional redundancy (i.e. the number of taxa performing a comparable ecosystem function) of woody riparian vegetation lining seasonal Mediterranean intermittent rivers to be a sensitive indicator of anthropogenic alteration that remained stable among sites of equivalent status. In Hungarian rivers, metric screening during development of new macroinvertebrate-based multimetric indices identified a combination of ecological traits and taxonomic descriptors as the most effective discriminator among status classes (Várbíró et al., 2011(Várbíró et al., , 2015. ...
Article
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Intermittent rivers and ephemeral streams (IRES) are common across Europe and dominate some Mediterranean river networks. In all climate zones, IRES support high biodiversity and provide ecosystem services. As dynamic ecosystems that transition between flowing, pool, and dry states, IRES are typically poorly represented in biomonitoring programmes implemented to characterize EU Water Framework Directive ecological status. We report the results of a survey completed by representatives from 20 European countries to identify current challenges to IRES status assessment, examples of best practice, and priorities for future research. We identify five major barriers to effective ecological status classification in IRES: 1. the exclusion of IRES from Water Framework Directive biomonitoring based on their small catchment size; 2. the lack of river typologies that distinguish between contrasting IRES; 3. difficulties in defining the ‘reference conditions’ that represent unimpacted dynamic ecosystems; 4. classification of IRES ecological status based on lotic communities sampled using methods developed for perennial rivers; and 5. a reliance on taxonomic characterization of local communities. Despite these challenges, we recognize examples of innovative practice that can inform modification of current biomonitoring activity to promote effective IRES status classification. Priorities for future research include reconceptualization of the reference condition approach to accommodate spatiotemporal fluctuations in community composition, and modification of indices of ecosystem health to recognize both taxon-specific sensitivities to intermittence and dispersal abilities, within a landscape context.
... Although several studies described effects of changes in the FD on ecosystem functions (e.g. Díaz and Cabido, 2001;Flynn et al., 2009;Frainer and McKie, 2015) and suggested the incorporation of functional indicators in environmental assessment (Bruno et al., 2016;Dolédec and Statzner, 2008;Young et al., 2008), freshwater ecosystems are still largely assessed using taxonomic indicators (e.g. EPT richnessi.e. ...
Article
Anthropogenic stress has been identified as main driver of freshwater biodiversity loss. Adverse effects on the biodiversity of freshwater organisms, such as macroinvertebrates, may propagate to associated ecosystem functions, such as organic matter breakdown (OMB). In this context, the functional diversity (FD) of communities has been suggested to be a more suitable predictor of changes in ecosystem functions than taxonomic diversity (TD). We investigated the response of TD and FD of invertebrate communities to an environmental stress gradient and the relation of both metrics to the rate of organic matter breakdown. For this, we sampled macroinvertebrates and determined OMB using leaf bags along an environmental stress gradient (i.e. changes in physicochemical and hydromorphological conditions) in 29 low-order streams. Taxonomic richness decreased with increasing environmental stress (r = −0.55) but was not related to OMB. Conversely, the Simpson diversity of communities was not associated with the gradient but correlated moderately (r = 0.41) with OMB. Of three functional diversity indices (functional richness, evenness and divergence), only functional richness correlated moderately with the stress gradient (r = −0.41) and any of the indices correlated with OMB. Nevertheless, functional metrics such as specific trait modalities and the total abundance of the dominant shredders correlated higher (r = 0.46 and 0.48) with OMB than the TD indices. Given a relatively small species pool in our study and methodical constraints such as the limited resolution of autecological information, the FD might perform better in other contexts and if focusing on response and effect traits for the stressor and ecosystem function under scrutiny, respectively.
... Current bioindicators could be tuned for temporary streams and rivers by quantifying and incorporating the sensitivity of the taxa to flow intermittency (García et al., 2014;Cid et al., 2015). Alternatives include the use of hyporheic invertebrates as bioindicators (Leigh et al., 2013b), the sampling of all uncommon microenvironment types to ensure that the entire community of a given site contributes to the assessment of the ecological status (Leitao et al., 2014), or the use of functional indices such as the functional redundancy of the riparian vegetation (Bruno et al., 2016). Thus, an appropriate suite of indicators would allow stakeholders to assess the ecological status of temporary streams and rivers within the same framework developed for permanent rivers (e.g., the Water Framework Directive (Council of the European Communities, 2000)). ...
Article
Temporary streams and rivers support biodiversity and provide valuable goods and services, especially in arid and semi-arid landscapes. However, temporary streams and rivers are being degraded at alarming rates owing to development, hydromorphological alteration, and disposal of waste water, among other stressors, and pressure will likely increase under global change. Here we propose that it is key to manage temporary streams and rivers as a unique ecohydrological type and not as a permanent waterway or a terrestrial ecosystem. Nevertheless, two challenges hinder this goal. First, data availability on intermittent low regimes and associated biotas is currently scarce. As a consequence, flow-ecology relationships in temporary waterways are largely unknown, and appropriate metrics to define and monitor their ecological status are missing. Second, the ecological and social values of temporary streams and rivers are often underestimated, being regarded as secondary ecosystems relative to permanent waterways. To conserve temporary streams and rivers, ecologists need to define them as unique ecosystems and conservation targets, and practitioners need to systematically collect biological and hydrological data in these ecosystems. Innovative approaches at the intersection of ecology, citizen science, and management, can also contribute to their management and conservation by: i) mapping them, ii) informing people about their ecological values, iii) safeguarding them from further human threats, iv) preserving their flow regime when managing reservoirs, wastewater treatment plants, and water abstraction activities, and v) restoring physically-degraded temporary reaches (e.g. due to gravel mining and off-road use) or reaches that have lost historical flows due to increasing drought severity, diversions, and groundwater overuse.
... De la Riva et al. (2017) and Fu et al. (2015) found FRic advantageous to FEve and FDiv for identifying functional diversity change affected by climate gradient. While Bruno et al. (2016b) concluded that FRic's predictive capacity exceeded by FR when assessing environmental stress on riparian woodlands. The question is which of the functional diversity indices can best predict the functioning of the ecosystem: the mechanism based on a single trait level weighted by abundance CWM, or alternatively that based on the complementarity of multiple trait levels non-weighted (FRic) or weighted by abundance (FEve, FDiv, FDis, Q). ...
Article
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Invasive alien species (IAS) poses a significant threat to plant biodiversity globally and even considered one of the largest threats to biodiversity, second to habitat loss. They behave as pioneer species in different landscapes, tolerant to disturbances, climatic conditions, high competitive potential and generalists in distribution. Their superior competitive ability results in the loss of native flora leading to extinction. The success of IAS generally attributed to differences in functional traits compared to less successful aliens as well as to native species. Several studies envisaged that the impacts of plant invasions are not universal and depend on the trait diversity of both, the introduced species and the resident community. Functional traits best describe the alien's success over natives , and they seem to be important attributes to conservation biology and ecosystem management. Moreover, their ecological impacts remain poorly understood due to lack of quantitative studies. In the present paper, we adopted the systematic literature review approach for collecting and analysing the scientific data. A total of 212 critical research papers and grey literature for last three decades were found meeting the aims, were collected from relevant sources. Present review emphasizes the differences in key functional traits between invasive alien plants and the native species which aid them to alter ecosystem functioning by modifying habitat according to their needs. We also focus on potential habitats for invasion based on a conceptual framework concerning response-effect traits. Review provides a quantitative assessment of invading species for their ecological performance , emerging problems and possible solution.
... In summary, riparian monitoring programs should also include those communities found along IRs. An indexing approach that allows the ranking of monitoring sites from good to poor such as using a Riparian Index of Biotic Integrity [57] or a Riparian Quality Index [58] should include parameters related to specific aspects of riparian IR communities responses to intermittence and human impact [59]. ...
Chapter
Intermittent rivers (IRs), rivers that periodically cease to flow, are common in the southern part of Montenegro and form a high proportion of the river networks in the Mediterranean and sub-Mediterranean parts of the country. IRs comprise of lentic, lotic, and dry patches that support rich aquatic, semiaquatic, and terrestrial communities that are largely neglected by ongoing biomonitoring programs. In this chapter, we present the recent research on the communities that inhabit the intermittent rivers of South Montenegro, with a focus on aquatic and terrestrial invertebrates and plants. For each group, we outline the characteristic communities found in the IRs. Future research should focus on including IRs in ongoing monitoring programs ensuring that their status assessment encompasses both their flowing and dry phases and their aquatic and terrestrial biotas.
... These ecological dimensions can be summarized by a range of indices and metrics such as taxonomic richness, tolerance-based biological indices, functional redundancy, and response diversity (Soria et al., 2019). Indices can be used to detect anthropogenic impact in different ecosystems (Mouillot, Graham, Villéger, Mason, & Bellwood, 2013;Soria et al., 2019) and monitor both natural and disturbed systems (Belmar et al., 2019;Bruno, Gutiérrez-Cánovas, Velasco, & Sánchez-Fernández, 2016). Further indices, such as functional diversity (Laliberte & Legendre, 2010), biodiversity (Izsák & Papp, 2000), and species richness (Heltshe & Forrester, 1983), are also useful for describing complex ecological contexts in a simple and universal way. ...
Article
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• Understanding soundscapes, that is, the totality of sounds within a location, helps to assess nature in a more holistic way, providing a novel approach to investigating ecosystems. To date, very few studies have investigated freshwater soundscapes in their entirety and none across a broad spatial scale. • In this study, we recorded 12 freshwater streams in South East Queensland continuously for three days and calculated three acoustic indices for each minute in each stream. We then used principal component analysis of summary statistics for all three acoustic indices to investigate acoustic properties of each stream and spatial variation in their soundscapes. • All streams had a unique soundscape with most exhibiting diurnal variation in acoustic patterns. Across these sites, we identified five distinct groups with similar acoustic characteristics. We found that we could use summary statistics of AIs to describe daytimes across streams as well. Most difference in stream soundscapes was observed during the daytime with significant variation in soundscapes both between hours and among sites. • Synthesis and Application. We demonstrate how to characterize stream soundscapes by using simple summary statistics of complex acoustic indices. This technique allows simple and rapid investigation of streams with similar acoustic properties and the capacity to characterize them in a holistic and universal way. While we developed this technique for freshwater streams, it is also applicable to terrestrial and marine soundscapes.
... All river reaches were under low human pressure as they fulfilled most of the 20 criteria to meet reference conditions in Mediterranean rivers (Sánchez-Montoya et al., 2009). These criteria include a wide range of human uses and disturbances on rivers and streams (e.g., diffuse sources of pollution, invasive species, land use intensity, riparian vegetation, river geomorphology, habitat conditions and hydrological alterations) and some general aspects of naturalness, and they have already been used to assess the impact of stressors in Mediterranean rivers (Bruno, Gutiérrez-Cánovas, Velasco, & Sánchez-Fernández, 2016). ...
Article
Aim To analyse temporal metacommunity dynamics in river networks in relation to hydrological conditions and dispersal. Location Fifteen river reaches from the Llobregat, Besòs 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.
... Some authors (e.g. Bruno et al., 2016;Hering et al., 2010) point out the absence of tools to evaluate the functional elements of the ecosystem as a weakness of the WFD assessment scheme. ...
Article
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The EU Water Framework Directive (WFD) assessment scheme has been putting in force the evaluation of freshwater ecosystems in Europe, including a new paradigm of ecological status. After almost 20 years since the WFD implementation, it is imperative to evaluate the efficiency of its standard assessment scheme and to explore the possibility of learning how to improve its effectiveness. That is the spirit of this review, aiming (i) to explore the existing literature on the WFD bioassessment scheme for assessing freshwater ecosystem health, particularly in lotic ecosystems (where the WFD scheme is most consolidated); (ii) to document which paths are suggested by the scientific community to improve the efficiency of the bioassessment in tackling current challenges. In the specific arena of bioassessment, we first identify the major constraints to the WFD full implementation in rivers. Second, we analyse retrospective Ecological Risk Assessment (ERA) as an evaluation approach supporting management actions that could inspire improvements in the WFD bioassessment scheme. Third, we review the advances and debate on complementary metrics to improve WFD evaluation protocols and/or the feasibility of the evaluation outcome. Fourth, a conceptual scheme for an improved evaluation strategy is presented. Our proposal essentially merges the WFD bioassessment scheme with the ERA philosophy, proposing a tiered approach of increasing complexity and spatial resolution, where expert judgement is included surgically at all decision stages. This scheme requires true integration of chemical, ecological and ecotoxicological LoE for a quantitative estimation of risks, and provides a comprehensive framework that accommodates tools and perspectives already suggested by other authors. Besides providing a literature review on the strengths and weaknesses of the current WFD bioassessment scheme, we wish to open way for the scientific discussion towards an improved conceptual scheme for the evaluation of ecosystem health.
... In this study, the variation of functional richness was not as obvious as that of the taxonomic richness from natural forest to low-intensity agriculture sites (Fig. 4 A and B). One explanation may be the existence of functional redundancy (Fig. S2), that is, different species have the same ecological function (Bruno et al. 2016;Lamothe et al. 2018). This finding was consistent with the study on Amazon fish communities which reported that environmental degradation would result in replacement of species having unique traits by functionally redundant ones (Leitao et al. 2018). ...
Article
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Expansion of agricultural and urban areas and intensification of catchment land-use increasingly affect different facets of biodiversity in aquatic communities. However, understanding the responses of taxonomic and functional diversity to specific conversion from natural forest to agriculture and urban land-use remains limited, especially in subtropical streams where biomonitoring programs and using functional traits are still under development. Here, we conducted research in a subtropical stream network to examine the responses of macroinvertebrate taxonomic and functional diversity to different types of land-use in central China. Our results showed that medium body size, univoltine, gill respiration, and slow seasonal development were much higher in natural forest sites, while certain traits related to strong resilience and resistance (e.g., small body size, fast seasonal development, bi-or multivoltine, abundant occurrence in drift, sprawler) dominated in high-intensity agriculture and urbanization sites. We further found that land-use compromised water quality (e.g., increases in total phosphate, conductivity and water temperature) and habitat conditions (e.g., high proportion of sand and silt, gravel, and channel width) accounted for the changes in trait composition based on a combination of RLQ and fourth-corner analysis. Moreover, natural forest sites presented relatively high values of functional richness than other land-use, demonstrating the importance of natural forest maintenance to promote high levels of functional diversity. However, taxonomic diversity indexes showed higher sensitivity to distinguish different types of land-use compared to functional diversity measures. Even so, given that certain trait categories showed significant relationships with specific local environmental stressors, trait-based approaches can provide reliable evidence to diagnose the cause of impairment and complement the results of the taxonomic-based approaches. Our findings support the idea that taxonomic and functional approaches should be integrated in river restoration and land-use management.
... In recent years, functional diversity indices have been used more frequently to assess environmental and human-induced impacts on functional diversity in riparian forests (Bruno et al., 2016;Lozanovska et al., 2018). Among these, the most frequently used are functional richness, functional evenness and functional divergence (e.g. ...
Article
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River hydromorphology has long been subjected to huge anthropogenic pressures with severe negative impacts on related ecosystems’ functioning and water quality. Therefore, improving river hydromorphological conditions represents a priority task in sustainable river management and requires proper assessment tools. It is well known that riparian vegetation plays a crucial role in sustaining river hydromorphological conditions. However, it has been nearly neglected in most hydromorphological assessment protocols, including the European Water Framework Directive (WFD). This paper reviews and synthesizes the relevance of riparian vegetation for river hydromorphology, focusing on its contribution to streamflow and sediment regime conditions. We also examine how riparian vegetation is considered in the WFD and how it is included in national hydromorphological protocols currently in use. Our findings point to a temporal mismatch between the date when the WFD came into force and the emergence of scientific and technologic advances in riparian vegetation dynamism and bio-geomorphic modeling. To overcome this misalignment, we present promising approaches for the characterization and assessment of riparian vegetation, which include the identification of vegetation units and indicators at multiple scales to support management and restoration measures. We discuss the complexity of riparian vegetation assessment, particularly with respect to the establishment of river-type-based reference conditions and the monitoring and management targets, and propose some attributes that can serve as novel indicators of the naturalness vs. artificiality of riparian vegetation. We argue that the hydromorphological context of the WFD should be revisited and offer guidance to integrate riparian vegetation in river hydromorphological monitoring and assessment.
... Traditionally, taxonomic-based metrics have been used as indicators of aquatic ecosystem integrity and conservation status (Bellucci et al., 2013;Bücker et al., 2010;Sotomayor et al., 2020). However, the functional trait approach (FTA) has emerged in the last decades as one of the most promising tools for bioassessment of freshwater ecosystems (Bruno et al., 2016). Functional traits are morphological, physiological, phenological or behavioural characteristics of organisms that influence their performance or fitness (Nock et al., 2016). ...
Article
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Aim This study aimed at investigating the taxonomic resolutions (TRs) of benthic macroinvertebrates for freshwater assessments in the scope of the functional trait approach (FTA). Location Macroinvertebrate samples were collected in 22 locations within the Paute River Basin (PRB), Ecuador, over three years (2010, 2011 and 2012). Methods Biological traits were allocated as scores to the macroinvertebrate data (at genus level) through fuzzy coding, using published data. The scores of each genus were used to derive scores for the corresponding family. These two sets of scores were standardized and compared, they were similar in 82% of the cases. Functional diversity (FD) was described by the rRao index, which showed no significant differences between coarse (family level) and fine (genus level) TRs. Cluster analyses using the K-means algorithm were performed to determine similarities between both rRao data sets. The WQ cluster number (K) was varied between 2 and 5 to determine a threshold K value (Kth), after which a WQ assessment differed as a function of the TR being used. Results Kth was 3. Family-level identification in the framework of the FTA in the PRB was suitable in detecting changes of macroinvertebrate assemblages (until Kth = 3). Main conclusions The proposed methodology could be implemented in other basins where decision-makers could decide whether the level of functional trait data similarity is sufficient for WQ management purposes and whether the defined Kth is acceptable. The reliability of the key methodological steps was assessed using performance statistics that have rarely been applied to ecological studies. Despite related research performed in other regions, the present study is the first South American attempt to investigate the effects of TR of benthic macroinvertebrates on freshwater bioassessments using functional traits.
... The use of traits in freshwater biomonitoring has gained traction because traits provide an indirect measure of functional responses and ways of predicting assemblages' responses to pollution through a mechanistic understanding of the trait-environment relationship. Functional indicators based on traits may also respond before changes in structure occur, providing an early indication of anthropogenic stressors (Bruno et al., 2016). The trait-based approach was thus applied in this study. ...
Thesis
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Agricultural land-use is a leading cause of water quality deterioration, biodiversity loss and impairment of stream functionality. Understanding the mechanisms by which agricultural land-use impair stream ecosystems is important for their effective management, especially in Africa. In this study, a combination of analytical tools, including macroinvertebrate taxonomic- and trait-based community analysis, functional indices, functional feeding groups and stable isotopes were used to investigate the effects of an increasing gradient of agricultural disturbance on the community composition, functional diversity, and food web of aquatic macroinvertebrates in the Kat River. Eight sites grouped into four site categories that represent a decreasing gradient of agricultural pollution (LUC 1< LUC 2 < LUC 3 and LUC 4) were selected. Macroinvertebrates and physiochemical variables and aquatic and terrestrial basal food sources were sampled from the eight sites over four sampling occasions; dry (winter and spring) and wet (summer and autumn) periods using the SASS 5 protocols. The taxonomy-based analysis showed different responses of macroinvertebrates to agricultural disturbance, with taxa such as Lymnaea spp., L. columella, Appasus spp. Biomphalaria spp., Trithemis spp. and Oligochaeta identified as potentially tolerant indicators of agricultural pollution. These taxa were positively correlated with the highly disturbed LUC 1 sites, and increasing levels of NH4-N, NO2-N, temperature and TDS. Conversely, Caenis spp., Afroptilum spp., Pseudocloeon piscis, Pseudocloeon spp., Baeti harrisoni, and Potamonautes spp. were sensitive to agricultural pollution, indicating strong negative associations with LUC 1 sites and NH4-N, NO2-N, salinity, temperature and TDS. Further, a multimetric index (MMI) was developed, validated and applied to assess agricultural disturbance in the Kat catchment. Of the 29 metrics that satisfactorily discriminated the LUC 4 site from the LUC 1, 2 and 3 sites, only eight metrics were non-redundant and integrated into Kat River MMI. The metrics integrated into the final MMI were Decapoda abundance, EPT/Chironomidae abundance, %EPT abundance, %Ephemeroptera abundance, %Caenidae abundance, %Hydropsychidae abundance, %Oligochaeta+chironomidae abundance and Shannon index. The developed MMI proved effective as a biomonitoring tool for assessing the ecological health of agricultural pollution in the Kat River. The trait-based analysis showed that traits such as haemoglobin, spiracle, adult aquatic life stage, active swimming and predatory lifestyle were positively correlated with LUC 1 sites, and were deemed tolerant-trait indicators of agricultural pollution. Shredding, medium body size (>10–20 mm), crawling and a preference for macrophytes were negatively correlated with LUC 1 sites, and were deemed sensitive-trait indicators of agricultural pollution in the Kat River. Functional diversity responded predictably to agricultural pollution, as functional indices such as functional richness, significantly declining along disturbance gradient during the dry and wet periods. The functional feeding group results revealed that gatherers and scrapers dominated in the Kat River, and together represented 0.27–0.43 of the invertebrate composition. Shredders were the lowest represented in the Kat River, with a relative abundance of 0.18. The FFG results showed that filter-feeders and predators increased in abundance along increasing environmental stress gradient, whereas shredders’ abundance decreased along the environmental stress gradient. Analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to estimate the contributions of aquatic and terrestrial resources to consumers across the four LUC and periods. Carbon contributions, determined using mixing models (Stable Isotope Analysis in R), revealed that consumers assimilated mainly aquatic sources (filamentous algae, macrophytes and biofilms), and this assimilation increased as agricultural disturbance increased across the two seasons. Terrestrial-derived food sources did not show evident variations among the LUCs, but C4 grasses changed along an increasing gradient of agricultural pollution during the two seasons. Further, there was enriched 15N of consumers, especially scrapers, predators and filter-feeders, along the disturbance gradient, whereas that of shredders declined along an agricultural disturbance gradient. NH4-N was the variable that affected consumers δ15N values, indicating a significant positive correlation with δ15N values for the majority of the consumers, especially gatherers, shredders and scrapers. The results of the study highlight the strength of a complementary approach to biomonitoring agricultural pollution in riverine systems. For example, the taxonomic analysis indicated changes in community composition, and the trait-based approach provided insights into the key stressors associated with agricultural pollution as a cause of water quality deterioration. The study contributes significantly to our understanding of riverine ecology in South Africa and, in particular the Kat River, in the context of agricultural pollution, which remains one of the leading causes of pollution of riverine ecosystems.
... In contrast, functional redundancy (which indicates the number of taxa making similar contributions to ecosystem functioning) can be unresponsive to natural stressors such as river drying until high disturbance intensities are reached (Aspin et al., 2019), but declines with human impacts if drying-tolerant taxa vary in both their traits and their impact sensitivities (Soria et al., 2020). This single negative response of functional redundancy to impacts ( Figure 1c) may facilitate its use in biomonitoring of temporary rivers (Bruno et al., 2016). ...
Article
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. 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 two biomonitoring indices that indicate ecological status. We analysed metrics based on the whole community and 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. 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. 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. 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, type‐specific and adaptable, promoting their ability to inform management actions that protect biodiversity in river ecosystems responding to climate change.
... Functional space quality was assessed by selecting the most relevant functional axes given the optimal number of dimensions (Maire et al., 2015). Functional redundancy, a metric that indicates the average representation of organisms playing similar functional roles in the ecosystem, was calculated by classifying the species into functional groups ( Figure S2) by means of clustering approaches based on a trait dissimilarity matrix (Bruno et al., 2016;Laliberté et al., 2010). ...
Article
Invasive alien species (IAS) are leading to the homogenisation of taxonomic and functional biodiversity, with negative consequences for key ecosystem processes in fresh water. Invasive signal crayfish (Pacifastacus leniusculus) is expected to disrupt detritus‐based food webs by affecting leaf breakdown and/or by decreasing invertebrate density and diversity through predation. The combination of per‐capita and abundance effects of P. leniusculus in invaded ecosystems is still largely unknown. A four‐week field experiment was established in Rabaçal and Tuela Rivers (NE Portugal) to assess effects of P. leniusculus on invertebrate taxonomic and functional diversity and leaf litter breakdown following a gradient of invasion. We controlled the presence and absence of crayfish by placing the animals and leaf litter inside cages at six sites (three sites per river) according to the crayfish in situ abundance (absent, low, high). Cages were covered with coarse‐ or fine‐mesh net to allow or prevent invertebrates from accessing the leaves. Results showed that higher crayfish in situ abundance led to a decrease in abundance, richness and Shannon diversity of invertebrates and to changes in the communities’ structures. Higher crayfish abundance led also to a decrease in invertebrate functional redundancy and an increase in the percentage of invertebrate taxa with resistance forms. Leaf litter breakdown increased with crayfish presence and decreased at sites with higher crayfish abundance. Overall, signal crayfish changed the community structure of invertebrates, with potential severe long‐term effects on native communities and leaf litter breakdown. Given the widespread distribution of signal crayfish (and other crayfish species), their ecological impacts should be assessed carefully, especially in pristine freshwater ecosystems such as those described here.
... Finalmente, dado que la redundancia funcional fue el índice funcional más sensible a la alteración, en el Capítulo 4 se testa su aplicabilidad como herramienta de biomonitoreo, comparándola con índices convencionales (taxonómicos y de calidad ecológica). Concretamente, se evaluaron tanto las respuestas de estos índices a los filtros antrópicos (alteración hidrológica y superficie agrícola) considerando el estrés natural subyacente (sequía), así como su capacidad para discriminar entre diferentes categorías de intensidad de perturbación humana (Bruno et al. 2016b). Aunque todos los índices (Tabla 1: capítulo 4) mostraron respuestas significativas, la redundancia funcional fue la más explicativa y sensible, siendo el único índice capaz de detectar impactos humanos de baja intensidad en todos los tipos de río. ...
Article
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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. 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.
Article
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Riparian vegetation is a crucial component of fluvial systems and serves multiple socio-ecological functions. The objective of this review is to follow the scientific trajectory of studies of riparian vegetation throughout history and across regions and fields of knowledge. Such a synthesis is challenging because riparian vegetation is an open co-constructed socio-ecological system at the crossroads of the biosphere, hydrosphere, lithosphere, atmosphere and anthroposphere; thus, it exhibits a wide range of ecological patterns and functioning depending on climatic, morphological and land-use contexts. To address this, we used qualitative and quantitative approaches in our review of the scientific literature. From the scientific perspective, how riparian vegetation is studied has changed over time (e.g. development of modeling and geomatic approaches) and varies among fluvial systems and geographic areas (e.g. its relation to groundwater is usually studied more in Oceania and Asia than on other continents). Thi review revealed the lack of a single and well-identified scientific community that focuses on riparian vegetation. This is probably due to the nature of the subject, which includes diverse fields of knowledge and several applied issues: biodiversity, forestry, water quality, hydromorphology, restoration, ecology, etc. Some topics are actively regenerated (e.g. biogeomorphological approaches) and others are emerging, which reflects general trends in ecology (e.g. functional approaches). The literature review indicates that a substantial amount of knowledge already exists; therefore, a major priority of our study is to produce a clear and integrative understanding of riparian zone functioning to address the inherent complexity of these zones and remain valid across a wide diversity of geographical contexts. It is also essential to develop detailed analysis of the sociocultural dimension of riparian vegetation to understand the ecology of riparian zones and to improve riparian vegetation management according t o local recommendations in order to maintain and improve its functions and services in the face of global changes
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Multiple studies have shown that biodiversity loss can impair ecosystem processes, providing a sound basis for the general application of a precautionary approach to managing biodiversity. However, mechanistic details of species loss effects and the generality of impacts across ecosystem types are poorly understood. The functional niche is a useful conceptual tool for understanding redundancy, where the functional niche is defined as the area occupied by a species in an n-dimensional functional space. Experiments to assess redundancy based on a single functional attribute are biased towards finding redundancy, because species are more likely to have non-overlapping functional niches in a multi-dimensional functional space. The effect of species loss in any particular ecosystem will depend on i) the range of function and diversity of species within a functional group, ii) the relative partitioning of variance in functional space between and within functional groups, and iii) the potential for functional compensation (degree of functional niche overlap) of the species within a functional group. Future research on functional impairment with species loss should focus on identifying which species, functional groups, and ecosystems are most vulnerable to functional impairment from species loss, so that these can be prioritized for management activities directed at maintaining ecosystem function. This will require a better understanding of how the organization of diversity into discrete functional groups differs between different communities and ecosystems.
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We used a phylogenetically based comparative approach to evaluate the potential for physiological studies to reveal patterns of diversity in traits related to susceptibility to an environmental stressor, the trace metal cadmium (Cd). Physiological traits related to Cd bioaccu-mulation, compartmentalization, and ultimately susceptibility were measured in 21 aquatic insect species representing the orders Ephemeroptera, Plecoptera, and Trichoptera. We mapped these experimentally derived physiological traits onto a phylogeny and quantified the tendency for related species to be similar (phylogenetic signal). All traits related to Cd bioaccumulation and susceptibility exhibited statistically significant phylogenetic signal, although the signal strength varied among traits. Conventional and phylogeneti-cally based regression models were compared, revealing great variability within orders but consistent, strong differences among insect families. Uptake and elimination rate constants were positively correlated among species, but only when effects of body size and phylogeny were incorporated in the analysis. Together, uptake and elimination rates predicted dramatic Cd bioaccumulation differences among species that agreed with field-based measurements. We discovered a potential tradeoff between the ability to eliminate Cd and the ability to detoxify it across species, particularly mayflies. The best-fit regression models were driven by phylogenetic parameters (especially differences among families) rather than functional traits, suggesting that it may eventually be possible to predict a taxon's physiological performance based on its phylogenetic position, provided adequate physiological information is available for close relatives. There appears to be great potential for evolutionary physiological approaches to augment our understanding of insect responses to environmental stressors in nature. comparative methods evolutionary physiology bioaccumulation phylogeny tradeoff W ith 6,500 species described to date in North America (1), aquatic insects are a diverse and ecologically important group (2), particularly in rivers and streams. For example, the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa) include 58 recognized families and 2,700 species (1). Among these many lineages, great diversity exists in morphology, life history characteristics, and physiology stemming from a long and complex evolutionary history. Although the origins of the Ephemeroptera are unknown (3), a general paradigm of the terrestrial ancestry of aquatic insects is widely accepted, with numerous invasions of freshwater habitats hypothesized throughout evolutionary history (4). Many of these invasions have entailed adaptive ''solutions'' that involve complex suites of traits that in combination determine the range of environmental conditions that a given taxon can tolerate. Some traits that arose in response to past environmental challenges may now render certain species relatively more susceptible to modern anthropogenic pollutants. These pollutants may be either entirely novel (e.g., organophosphate insecticides) (see ref. 5) or were historically present at much lower concentrations in natural environments than they are in many ecosystems today (e.g., trace metals) (6). This variation in susceptibility has practical implications, because the ecological structure of aquatic insect communities is often used to indicate the ecological conditions in freshwater systems (7-9). Differences among species' responses to environmental stressors can be profound, but it is uncertain whether the cause is related to functional ecology [usually the assumption (10, 11)] or physiological traits (5, 12-14), which have received considerably less attention. To the degree that either is involved, their link to phylogeny and evolutionary history remains poorly understood. Here, we ask whether the tendency for related species to be similar (i.e., phylogenetic signal) (15, 16) extends to physiological traits that contribute to sensitivity to the stressor: cadmium. Generalizations about phylogenetic linkages to stress responses have been hindered to date by the limited number of species that can be studied. We overcome this hurdle by using highly developed methodologies for efficiently quantifying critical processes that control sensitivity to dissolved cadmium (see refs. 13, 17, and 18) (Fig. 1). These physiological processes have previously been considered in a conceptual model of metal toxicity (19) that explicitly assumes that chronic toxicity in nature is the manifestation of metal accumulation at target sites (i.e., metal-sensitive sites) that ensues when the rate of metal influx exceeds the combined rates of metal excretion and detoxification. In practice, the model can be tested by combining bioaccumulation kinetics (see ref. 17) and subcellular fractionation (e.g., refs. 18 and 20). We have used this integrated approach to reconcile apparent discrepancies between insect responses to trace metals in toxicity assays and in nature (13), to infer Cd sensitivity differences among predaceous stoneflies (14), and to understand the mechanisms underlying the metal tolerance of a caddis fly (21). We used phylogenetic analyses (22-30) to explore physiological processes related to dissolved Cd susceptibility in 21 field-collected aquatic insect species representing eight EPT families [supporting information (SI) Table S1]. We tested for correlations and possible trade-offs among traits and used traits in combination to predict the more emergent property (sensitivity) in each of these species. We asked whether phylogenetic approaches (15, 16, 22-30) are potentially more powerful than traditional functional guild approaches (e.g., ref. 31) for predicting sensitivity differences among species. We compared statistical models that include body weight, feeding strategy, and lineage as independent variables by using both conventional and
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