Article

Different responses of functional traits and diversity of stream macroinvertebrates to environmental and spatial factors in the Xishuangbanna watershed of the upper Mekong River Basin, China

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  • Centro Universitario Litoral Norte Universidad de la República
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Abstract

Functional traits and diversity indices have provided new insights into community responses to stressors. Most traits of aquatic organisms have frequently been tested for predictability and geographical stability in response to environmental variables, but such tests of functional diversity indices are rare. We sampled macroinvertebrates at 18 reference sites (RS) and 35 disturbed sites (DS) from headwater streams in the upper Mekong River Basin, Xishuangbanna (XSBN), China. We selected 29 qualitative categories of eight traits and then calculated five functional diversity indices, namely functional richness (FRic), functional evenness (FEve), functional dispersion (FDis), functional divergence (FDiv) and Rao's Quadratic Entropy (RaoQ), and two trait diversity indices, namely trait richness (TR) and trait diversity (TD). We used combination of RLQ and fourth-corner to examine the response of traits and functional diversity to the disturbance and environmental variables. We used variance partitioning to explore the relative role of environmental variables and spatial factors in constraining trait composition and functional diversity. We found that the relative frequency of ten trait categories, and the values of TD, TR, FRic and FDis in RS were significantly different (p<0.05) from DS. In addition, the seven traits (except for "habit") demonstrated a predictable response of trait patterns along the integrative environmental gradients. Environmental variables significantly contributed to most of the traits, functional diversity and trait diversity. However, spatial variables were mainly significant in shaping ecological traits, FRic and FEve. Our results confirm the dominant role of environmental variables in the determination of community trait composition and functional diversity, and substantiate the contribution of spatial vectors in explaining the variance of functional traits and diversity. We conclude that the traits "Refuge", "External protection", "Respiration" and "Body shape", and diversity indices FDis, TD, and TR are promising indicators of stream conditions at XSBN.

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... While a number of studies have used the traits and ecological preferences to assess the effect of different stressors such as metals, cargo ship, sedimentation and organic waste (Pallottini et al., 2017;Akamugwuna et al., 2019;Desrosiers et al., 2019), not much has been done in terms of how urban pollution influence the distribution pattern of macroinvertebrates traits and ecological preferences, particularly in Africa. The increasing recognition accorded to the TBA could be attributed to empirical evidence suggesting that i) it is less spatially constraint compared to the taxonomic approach, ii) has more direct link to ecosystem function iii) has potential for impact diagnosis (Ding et al., 2017;Milosevic et al., 2018;Desrosiers et al., 2019). Given the growing recognition of the trait-based approach (Poff et al., 2006;Liess et al., 2008;Stazner and Beche 2010;Ding et al., 2017;Pallottini et al., 2017); it was asked whether traits and ecological preferences would respond differentially to a gradient of urban pollution in the Niger Delta region of Nigeria? ...
... The increasing recognition accorded to the TBA could be attributed to empirical evidence suggesting that i) it is less spatially constraint compared to the taxonomic approach, ii) has more direct link to ecosystem function iii) has potential for impact diagnosis (Ding et al., 2017;Milosevic et al., 2018;Desrosiers et al., 2019). Given the growing recognition of the trait-based approach (Poff et al., 2006;Liess et al., 2008;Stazner and Beche 2010;Ding et al., 2017;Pallottini et al., 2017); it was asked whether traits and ecological preferences would respond differentially to a gradient of urban pollution in the Niger Delta region of Nigeria? Odume et al. (2018a) and Edegbene (2020) distinguished between traits and ecological preferences. ...
... The differential responses of traits/ecological preferences to urban pollution suggest that they may be suitable as indicators of urban pollution. The present study thus adds to the already existing studies indicating the importance of the traitbased approach for monitoring freshwater ecosystems health (Liess et al., 2008;Ding et al., 2017;Pallottini et al., 2017;Desrosiers et al., 2019). ...
Article
Urbanisation of riverine landscape is an increasing threat to the functionality of river ecosystems. In this study, we identify and classify macroinvertebrates indicator signature traits and ecological preferences.We hypothesised that urban pollution would differentially influence the distribution of macroinvertebrate traits and ecological preferences along a gradient of water quality deterioration. Hence, we identified and classified potential biological indicators traits and ecological preferences that were deemed tolerant of or sensitive to urban pollution gradient in the Niger Delta region of Nigeria. Physico-chemical variables (water temperature, depth, flow velocity, dissolved oxygen, biochemical oxygen demand, electrical conductivity (EC), nitrate, phosphate), and macroinvertebrates were collected seasonally during the wet and dry seasons once in a month in 11 stations in eight river systems. The results based on RLQ, Fourth-corner and Kruskal-Wallis analyses indicate that traits/ecological preferences such as tegumental/cutaneous respiration, cased/tubed body armouring, a preference for silty water, bivoltinism, burrowing and a high tolerance for oxygen depletion, were statistically significantly associated with the heavily impacted stations. These traits were positively correlated with physico-chemical variables such as EC, nitrate and phosphate indicative of urban pollution. On the other hand, traits/ecological preferences such as permanent attachment, crawling, swimming, univoltinism and a moderate sensitivity to oxygen depletion were associated with the least impacted stations and were negatively correlated with physico-chemical variables indicative of urban pollution. Overall, the observed differential responses of traits and ecological preferences to urban pollution along a gradient of water quality impairment suggest that traits and ecological preferences can serve as useful biological indicators and thus supports the growing evidence of the utility of the trait-based approach.
... These taxa exhibit a wide range of sensitivities, and are highly tolerant of depleting DO, which enables them to survive in varying environmental conditions (Gerth et al., 2017). For example, some species of chironomids possess specialised adaptive features, such as haemoglobin, that allow the animals to survive in highly organic, oxygendepleted environments (Ding et al., 2017;Huang et al., 2015). However, the lower taxonomic resolution of Oligochaeta and Chironomidae may have limited their responses to pollution in the Kat River. ...
... For example, researchers have consistently reported high levels of nutrients and suspended solids, depletion of dissolved oxygen and increased levels of dissolved salts in the Kat River system (e.g., Lerotholi, 2005;Mgaba, 2018). Agricultural disturbances affect not only taxonomic composition and richness, but also the functional measures of macroinvertebrate communities (Archaimbault et al., 2010;;Mondy et al., 2016;Ding et al., 2017). The Kat River is a typical semi-urban river that is a biodiversity hotspot for communities of aquatic and terrestrial organisms (Soviti et al., 2003). ...
... Mouillot et al. (2013b) predicted that functional richness would not be sensitive to disturbance intensity because low disturbance may deplete communities of rare species with combinations of sensitive traits without immediate effect on species composition or functional richness. Nevertheless, since functional richness is regarded as a primary component of functional diversity (see , the significant decrease in functional richness in the highly agriculturally influenced sites observed in the Kat River suggests an indication of the change in ecosystem function resulting from loss of niche space for species due to disturbance (Schmera et al., 2012;Ding et al., 2017). Further, functional richness reflects species resource-use efficiency and community stability, which may have been affected in the highly disturbed sites, especially in the dry season (de Castro et al., 2018). ...
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.
... Here, we investigated the EMS of stream diatoms and macroinvertebrates from the same set of sites in three regions in China ( Figure 1). These regions show high regional variation of environmental heterogeneity because they located at different climatic zones and experienced different degrees of urbanization (Chen et al., 2019;Ding et al., 2017;Wang et al., 2012). Stream communities across a set of sites within a region were defined here as a metacommunity. ...
... In this study, we used a unique data set containing three geographi- land use change such as a decline in forest cover (Ding et al., 2017;Wang et al., 2012). Land use in ITR is dominated by livestock grazing, but much of the upper basin supports natural forests (Chen et al., 2019). ...
... The study regions are evidently different in natural climatic conditions and human land use characteristics (Figure 1; Table 1; Chen et al., 2019; Ding et al., 2017; Wang et al., 2012), thus showing notable differences in among-region environmental heterogeneity. MKR is a tropical rain forest area F I G U R E 1 Geographic locations of the sampling sites in three regions: the upper section of the Mekong River (MKR) in Xishuangbanna prefecture, the middle section of Qiantang River (QTR) in Zhejiang Province and the Irtysh River (ITR) in Xijiang autonomous region characterized by a tropical monsoon climate(Ding et al., 2017). QTR and ITR are characterized by a subtropical monsoon climate(Wang et al., 2012) and a temperate arid climate(Chen et al., 2019) respectively. ...
Article
Aim Idealized metacommunity structures (i.e. checkerboard, random, quasi-structures, nested, Clementsian, Gleasonian, and evenly spaced) have recently gained increasing attention, but their relationships with environmental heterogeneity and how they vary with organism groups remain poorly understood. Here we tested two main hypotheses: (1) gradient-driven patterns (Clementsian and Gleasonian) occur frequently in heterogeneous environments, and (2) small organisms (here, diatoms) are more likely to exhibit gradient-driven patterns than large organisms (here, macroinvertebrates). Location Streams in three regions in China. Taxon Diatoms and macroinvertebrates Methods The stream diatom and macroinvertebrate data, as well as the environmental data collected from the same set of sites were used to examine the idealized metacommunity structures via the elements of the metacommunity structure (EMS; coherence, turnover, and boundary clumping) analysis in three regions. We extended the traditional EMS approach by ordering sites along known environmental gradients. Results We found that Clementsian structure with high degrees of coherence and turnover, and significantly positive clumping was typically observed in the high-heterogeneity regions, whereas randomness was prevalent in the low-heterogeneity region. Macroinvertebrates exhibited clearer Clementsian structures compared with diatoms, while diatoms showed more randomness compared with macroinvertebrates, indicating a stronger role of environmental filtering for macroinvertebrates than diatoms. In most cases, the results of the more novel EMS approach differed from the results of the traditional EMS technique. Main conclusions Our results suggested that the occurrence of different metacommunity structures may be related with the degree of regional environmental heterogeneity. However, diatom metacommunities were more random than those of macroinvertebrate, and such an unexpected result may result from different dispersal abilities between the two organism groups. In addition, we found that the novel EMS approach increased power in discerning metacommunity structure in comparison to the traditional EMS technique.
... While taxonomical assessments have often been used to assess the effects of multiple stressors on communities, they are bound to the regional species pool which reduces their potential for generalization. To overcome this limitation, trait-based assessments, which rely on the compilation of community specific trait databases to characterize community niche breadth, have recently been getting more momentum (Ding et al., 2017). Trait assessments highlight the functional significance of species, that is, what they can do. ...
... Despite linking macroinvertebrate communities to stream-wide ecosystem functions such as decomposition and productivity, traitbased assessments in multiple-stressor research tend to be restricted to observational rather than manipulative field experiments (Ding et al., 2017;Dolédec et al., 2011;Mor et al., 2019). Further, mesocosm studies are an invaluable tool to ecologists by giving the ability to control and replicate multiple-stressor treatments (Woodward et al., 2010). ...
... Together, these traits give an overall description of the ecological characteristics of the community and also represent aspects that are susceptible to having a close relationship with the manipulated stressors. Further, the traits provide information about the resilience and resistance of the community as well as more general biological characteristics (Ding et al., 2017;Dolédec et al., 2011;Li et al., 2019). Trait information was adapted from the literature (Ding et al., 2017;Merritt et al., 2008;Poff et al., 2006) and online databases (Appendix S2) (Schmidt-Kloiber & Hering, 2015). ...
Article
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Ensuring the provision of essential ecosystem services in systems affected by multiple stressors is a key challenge for theoretical and applied ecology. Trait-based approaches have increasingly been used in multiple-stressor research in freshwaters because they potentially provide a powerful method to explore the mechanisms underlying changes in populations and communities. Individual benthic macroinvertebrate traits associated with mobility, life history, morphology and feeding habits are often used to determine how environmental drivers structure stream communities. However, to date multiple-stressor research on stream invertebrates has focused more on taxonomic than on functional metrics. We conducted a fully crossed, 4-factor experiment in 64 stream mesocosms fed by a pristine montane stream (21 days of colonisation, 21 days of manipulations) and investigated the effects of nutrient enrichment, flow velocity reduction and sedimentation on invertebrate community, taxon, functional diversity and trait variables after 2 and 3 weeks of stressor exposure. 89 % of the community structure metrics, 59 % of the common taxa, 50 % of functional diversity metrics and 79 % of functional traits responded to at least one stressor each. Deposited fine sediment and flow velocity reduction had the strongest impacts, affecting invertebrate abundances and diversity, and their effects translated into a reduction of functional redundancy. Stressor effects often varied between sampling occasions, further complicating the prediction of multiple-stressor effects on communities. Overall, our study suggests that future research combining community, trait and functional diversity assessments can improve our understanding of multiple-stressor effects and their interactions in running waters.
... We hypothesized that communities from different types of landuse would differ, with natural forest supporting macroinvertebrate communities that are more functionally diverse. Second, certain traits have been proven to serve as a promising proxy of community resilience and resistance in response to land-use changes (Dolédec et al. 2011(Dolédec et al. , 2006Ding et al. 2017;Castro et al. 2018), we predicted that the aquatic organisms possessing traits linked to high resilience and resistance (e.g., bi-or multivoltine, fast seasonal development, short life span, abundant occurrence in drift and burrowers) increased in both agriculture and urbanization land-use. Third, trait-based approach can provide early warning signals of ecosystem processes responding to land-use changes before actual species loss (Dolédec and Statzner 2008;Leitao et al. 2018), we predicted that functional diversity indexes could better distinguish the effects of different types of land-use compared to taxonomic diversity indexes. ...
... Twelve biological traits with thirty-eight different trait categories (Table 1) were considered. These biological traits describe macroinvertebrate properties related to resilience and resistance (voltinism, development, adult life span, body size, body shape, armoring, occurrence in drift, swimming ability, flying ability, habit), and physiological and biological adaption (respiration and trophic groups) (Morse et al. 1994;Poff et al. 2006;Zuellig and Schmidt 2012;Ding et al. 2017;Wang et al. 2019). Additionally, these traits are sensitive to anthropogenic stressors and thus serving as a promising tool in describing the functional responses of benthic macroinvertebrates in this region (Li et al. 2019(Li et al. , 2020. ...
... The observed patterns of certain traits related to community resistance are in line with our second prediction, with high proportions of burrower, soft body, and strong drift ability found in high-intensity agriculture and urbanization sites with higher proportions of sand and silt. A human-induced homogeneous environmental condition (e.g., higher proportions of sand and silt) would expose aquatic organisms to drastic interference (Ding et al. 2017), and only taxa with strong drift capacity and soft bodied forms may better avoid physical disturbance (Castro et al. 2018). On the contrary, we found that clingers occurred more frequently in natural forest sites with high proportion of boulder and cobble, such as some Plecoptera (e.g., Tetropina sp.) and Ephemeroptera (e.g., Heptagenia sp. and Rhithrogena sp.) taxa. ...
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.
... Biological traits were used to reveal the changes of structures and functions of assemblages and indicate similar responses when the ecosystems were under the same environmental stressors such as nutrient loading and pollutant gradients (Ding et al., 2017;Hu et al., 2019;Brauko et al., 2020). For bivalve aquaculture, although the cultured bivalves alter the surrounding environment through similar ways such as organic enrichment and nutrient release (Lacoste et al., 2019), functional compositions of macrofaunal assemblage may vary with farms. ...
... Compositional and functional alterations in biotic communities have been wildly used to quantify the disturbance caused by both natural and anthropogenic stressors (Ding et al., 2017;Teichert et al., 2018;Manfrin et al., 2020). Most of the compositional and functional indices in this study were associated with the density of cultured bivalve according to LMMs. ...
... In our study, the varied R c 2 (values ranged from 0.22 to 0.75) of benthos assemblage index indicates a large proportion of deviance remained not explained by the fixed factors. The performance of the present models was consistent with other studies on the community responses indicated by compositional and functional indices (Ding et al., 2017;Teichert et al., 2018). Spatial variability largely contributes to the stochastic distribution of benthic taxa (Porst and Irvine, 2009), reducing the proportion of deviance explained by fixed variables. ...
Article
Coastal bivalve aquaculture is considered to have large impacts on the structure and functions of macrofauna assemblages. In the present study, we evaluated the macrofauna assemblages from 12 bivalve farms along the China coast using 11 compositional and functional indices and 15 biological traits within four major categories. Linear mixed models (LMMs) were used to identify the most influential variable on the selected indices. The RLQ and fourth-corner approaches were used to investigate the response of functional traits composition to the characteristics of bivalve farms. Our results suggest that the increased densities of cultured bivalve had a negative impact on the organisms sharing similar function traits but the ecosystem could still maintain the functional richness because those organisms were mainly on the redundant group, and their loss favored a more balanced distribution of taxa and biological traits. Additionally, biological trait compositions of macrofaunal assemblages were more similar within farms using the same culture method. Small-sized opportunistic deposit feeders were likely to appear in cage farms, and predators were more attracted by rope farms. In bottom-based bivalve farms, filter feeders dominated but carnivores and crawlers were significantly lower compared to the other culture methods. We conclude that functional redundancy is a critical indicator for identifying the suitable scale and intensity of bivalve aquaculture. From the perspective of maintaining biological traits, bottom-based culture causes less ecological impact compared to off-bottom culture, the latter is more suitable in areas with relatively deep water and strong current and water exchange rate.
... Apart from pesticide application, the TBA has also found utility in assessing the effects of other stressors such as urbanisation, industrialisation, and sedimentation (Mondy & Usseglio-Polatera, 2014;Ding et al., 2017;Pallottini et al., 2017;Akamaguana et al., 2019). For example, Mondy & Usseglio-Polatera (2014) used life-history traits to assess specific risks of streams undergoing multiple pressures such as urbanisation and sedimentation. ...
... They found that shredders, which feed on leaves, were highly sensitive to sediment accumulation in their studied streams. Ding et al. (2017) assessed different responses of traits to environmental and spatial variables and found that environmental variables affect the functional and trait diversity of macroinvertebrates, while spatial variables shape the ecological traits of macroinvertebrates. Pallottini et al. (2017) assessed functional trait responses to agricultural and industrial pollution and concluded that functional traits are relevant for biomonitoring stressed freshwater systems. ...
... America (Tomanova et al., 2008), in Asia (Aazami et al., 2015;Ding et al., 2017;Forio et al., 2018) and in Africa (Akamagwuna et al., 2019;Odume, 2020). For instance, Berger et al. (2018) identified taxa and traits responses to specific stressors, such as industrialisation and urbanisation. ...
Thesis
Riverine systems are increasingly subjected to pollution due to rapid urbanisation, industrialisation, and agricultural activities. Increasing pollution in freshwater systems impairs water quality, causes biodiversity loss and impairs aquatic ecosystem functionality and supply of ecosystem services. Rivers in the Niger Delta region of Nigeria are particularly vulnerable to urban pollution and agricultural activities as natural forests are increasingly replaced by urbanisation and agriculture. The differential effects of these pressures on the ecological processes of these river systems are poorly explored, as is the development of appropriate biomonitoring tools for routine monitoring of river health. In this study, a physico-chemically-based approach and macroinvertebrate trait- and taxonomic- approaches were developed to better understand the effects of multiple pressures on riverine systems, while developing multimetric indices to enable sustainable management of rivers within the region. Sixty-six stations in 20 river systems within the Edo and Delta States of the Niger Delta ecoregion were monitored seasonally for a period of five (2008–2012) years. The physico-chemically based approach makes apparent the extent of degradation of rivers and streams in the Niger Delta. For each dominant land use type, river stations were classified into least impacted stations (LIS), moderately impacted stations (MIS) or heavily impacted stations (HIS). Of 11 stations within urban catchments, only two were considered least impacted, suggesting that urgent measures are necessary to revise the current trajectories of urban rivers within the region. Most of the stations designated as MIS and HIS in the urban and urban-agriculture catchments were found to be significantly correlated with increased nutrients, EC and BOD5. Characteristics of most of the MIS and HIS within rivers in urban catchments evidenced the so-called urban stream syndrome, a state of persistent degradation of urban streams. The results of the traits and ecological preferences approach showed traits sensitive to urban and urban-agriculture pollution. Traits and ecological preferences that were associated with the LIS iii include the possession of hardshell, moderate and high sensitivities to oxygen depletion, very large body sized individuals (>20-40mm), swimmers, flattened body shape, a preference for temporary attachment, crawling, respiration with aerial/vegetation, possession of breathing tubes, possession of strap or other apparatus for respiration, streamlined body, and a high sensitivity to oxygen depletion. Permanent attachment as an ecological preference associated with LIS was also positively correlated with increasing dissolved oxygen (DO) and was deemed a pollution sensitive ecological preference. The possession of very small body size (<5mm), associated with HIS, was deemed a pollution-tolerant trait and was negatively correlated with DO, confirming the deteriorating state of the urban and urban-agricultural rivers. The impact of urban-forestry pollution on the distribution pattern of macroinvertebrate traits and ecological preferences was also explored in the selected rivers. Traits and ecological preferences such as possession of hard-shell, large body size, and grazing as a feeding preference which were significantly positively associated with the LIS, were also either significantly positively correlated with DO, or significantly negatively correlated with increasing any two of flow velocity, water temperature, BOD5 and nutrient. These traits and ecological preferences were deemed sensitive in forested rivers receiving urban pollution. Further, burrowing, the pupa aquatic stage, and predation which were significantly positively associated with HIS on the RLQ ordination, were also significantly negatively associated with DO. These traits were deemed tolerant of forested systems receiving urban pollution. Multimetric indices (MMI) were developed, validated and applied for urban, urban-agriculture and urban-forested (MMI-urban, MMI-urban-agric and urban-forest) areas. Of the 26 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban, only five metric were retained for integration into MMI-urban, they are log VeL, Hemiptera abundance, % Coleoptera + Hemiptera, % Chironomidae + Oligochaeta and Evenness index. Further, of the 18 metrics that satisfactorily discriminated between the LIS, the MIS, and the HIS for MMI-urban- iv agric, only 12 metrics were retained and nine proved to be redundant. The nine metrics represent different measures; two of them were retained in addition to Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness. The two metrics selected in addition to the Chironomidae/Diptera abundance, % Odonata and Oligochaeta richness were the Margalef index and the logarithm of relative abundance of sprawler. For the MMI-urban-forest, 14 metrics satisfactorily discriminated between the LIS, the MIS, and the HIS, and 12 metrics were retained and 11 proved to be redundant. The non-redundant metric was Trichoptera abundance. Three metrics were further selected in addition to the Trichoptera abundance which include % Chironomidae + Oligochaeta, Coleoptera + Hemiptera richness and Shannon diversity. The MMI-urban and MMI-urban-agric indices performed better for LIS designated stations compared to the MIS and HIS deignated stations. The developed indices proved effective as biomonitoring tools for assessing the ecological health of rivers in the urban and urban-agriculture catchments within the Niger Delta. Overall, the results of the macroinvertebrate traits and ecological preferences, and taxonomic approaches showed the strength in the complementarity of both approaches in developing biomonitoring tools for assessing levels of deterioration in riverine systems. The study contributes significantly to understanding the ecology of riverine systems in the Niger Delta, particularly those subject to urban stresses, agricultural activities and urban pollution in forested systems, and thus makes an important contribution to the science and practice of biomonitoring in Nigeria where such studies are sparse.
... Globally, there is a move toward the combine use of physicochemical and biological monitoring tools for assessing ecological conditions of riverine ecosystems (Arimoro, Odume, Uhunoma, & Edegbene, 2015;Bonada, Prat, Resh, & Statzner, 2006;Ding et al., 2017;Pešić et al., 2019;Shull, Smith, & Selckmann, 2019;Stevenson, Zalack, & Wolin, 2013). It has been acknowledged that physicochemical monitoring alone is inadequate, as results only represent the time and spot from which samples were collected, as well as being very expensive, particularly if a wide range of variables are to be monitored and analyzed (Edegbene et al., 2019;Odume, Muller, Arimoro, & Palmer, 2012). ...
... Studies testing metrics for integration into multimetric indices have often ended up with one or two trait-based metrics in the final indices, indicating that the present study, which found only a single trait to be highly sensitive and non-redundant was in accordance with most other studies (e.g.,Baptista et al., 2007;Fierro et al., 2018;Gieswein et al., 2019;Ntislidou et al., 2018). The inclusion of the trait-based metric into the final MINDU is particularly useful because while taxonomic metrics relate to structural measure, traits relate to the functional aspects of the biota(Desrosiers et al., 2019;Ding et al., 2017;Monaghan & Soares, 2012).The five candidate metrics integrated into the MINDU are sparsely reported as metrics for development of multimetric indices except the %Hemiptera + Coleoptera and Hemiptera abundance(Aura et al., 2017;Edegbene et al., 2019). This informs the selection of %Coleoptera + Hemiptera and Hemiptera abundance for integration into the MINDU even when they were redundant. ...
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Urban pollution of riverine ecosystem is a serious concern in the Niger Delta region of Nigeria. No biomonitoring tool exists for the routine monitoring of effects of urban pollution on riverine systems within the region. Therefore, the aim of this study was to develop and apply a macroinvertebrate‐based multimetric index for assessing water quality condition of impacted urban river systems in the Niger Delta region of Nigeria. Macroinvertebrate and physicochemical samples were collected from 11 stations in eight river systems. Based on the physicochemical variables, the stations were categorized into three impact categories namely least impacted stations (LIS), moderately impacted stations (MIS) and heavily impacted stations (HIS). Seventy‐seven (77) candidate metrics were tested and only five: Hemiptera abundance, %Coleoptera + Hemiptera, %Chironomidae + Oligochaeta, Evenness index and Logarithm of relative abundance of very large body size (>40–80 mm) were retained and integrated into the final Niger Delta urban multimetric index (MINDU). The validation dataset showed a correspondence of 83.3% between the index result and the physicochemically‐based classification for the LIS and a 75% correspondence for the MIS. A performance of 22.2% was recorded for the HIS. The newly developed MINDU proved useful as a biomonitoring tool in the Niger Delta region of Nigeria and can thus be used by environmental managers and government officials for routine monitoring of rivers and streams subjected to urban pollution. Macroinvertebrate‐based urban multimetric index was developed for Niger Delta region of Nigeria. The newly developed multimetric index proved useful for assessing ecological health of river systems subjected to urban pollution.
... The application of functional traits and diversity indices as indicators of stressors of aquatic organisms is scarce (Ding et al., 2017). ...
... However, microhabitat preference (such as substrate type) is negligible at taxonomic levels as a consequence of the extreme environmental conditions (Cejudo-Figueiras, Álvarez-Blanco, Bécares, & Blanco, 2011;Lengyel et al., 2016). This result further emphasizes the primarily role of local factors (Bichoff et al., 2018) and of the strong environmental filters on the structure and function of the communities, (Ding et al., 2017;Soininen, 2012) even in saline ecosystems . ...
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Abstract Saline lakes, among the most seriously endangered ecosystems, are threatened due to climate change and human activities. One valuable feature of these environments is that they constitute areas of high biodiversity. Ecologists are, therefore, under great pressure to improve their understanding of the effects of natural and anthropogenic disturbances on the biodiversity of saline lakes. In this study, a total of 257 samples from 32 soda pans in Central Europe between 2006 and 2015 were examined. The effects of environmental variables and of geographical and limnoecological factors on functional diversity were analyzed. Furthermore, the explanatory power of the trait‐based approach was assessed, and the applicability of the indices for biomonitoring purposes was determined. It was found that low habitat heterogeneity and harsh environments lead to the selection of a small number of suitable traits, and consequently, to a naturally low level of functional diversity. Anthropogenic activities enhance diversity at functional level due to the shift toward freshwater characteristics. On the regional scale, the effects of the region and status (natural, degraded, reconstructed) on diatom functional diversity were significant and more pronounced than that of the environmental and other limnoecological factors. The degree of variance found in functional diversity ascribed to environmental variables is five times greater in the case of the application of a trait‐based approach, than when a taxonomic one is employed in the literature. Each of the tested functional diversity indices was sensitive to the most important environmental variables. Furthermore, these were type‐specific and proved to be more complex indicators than taxonomic metrics. It is possible to suggest four functional diversity indices (FGR, FRic, FDis, and FDiv) which emphasize their independence from substrate and seasonal variations for ecological status assessment and conservation planning.
... The average species richness and average density of macroinvertebrates was 31 and 437 ind./m 2 in the 5 DFGs. Compared to other mountain rivers which were not affected by natural disasters in Yunnan Province, the standing stock of macroinvertebrates in DFGs was significantly lower (Ding et al., 2017;Jiang et al., 2009;Wang and Ji, 2012). For example, the average benthic species richness in the upper reaches of Chishui River was 179, and the average density was 3248 ind./m 2 . ...
... The same or different spatial patterns of functional traits can be attributed to environmental changes and trade-offs between different functions (Ding et al., 2017). Different DFGs have different hydrological, topographical, and geomorphic characteristics, so the relative abundance of different rivers at different grades is different. ...
... Trait-based studies based on macroinvertebrates are among the most explored aquatic biota for biomonitoring rivers (Yadamsuren et al., 2020). Anthropogenic pollution has been reported to negatively affect the distribution patterns of macroinvertebrate traits in riverine systems, with traits responding differential along stress gradients (Desrosiers et al., 2019;Ding et al., 2017;Edegbene et al., 2020aEdegbene et al., , 2021Ntloko et al., 2021). However, trait-based studies using the whole macroinvertebrate dataset may be challenging due to the complexity of the dataset and a dearth of autecological information for most macroinvertebrate taxa, particularly Afrotropical species. ...
... These traits were considered rural sensitive traits because they indicated a strong significant negative association with at least one of the physicochemical indicators of semi-urban pollution. Morphological and respiratory traits such as spherical body shape and gills are reported to be sensitive to unstable microhabitats (Ding et al., 2017;Doretto et al., 2018;Magbanua et al., 2010). Likely, elevated sediments and acidity from fertilisers and pesticides use affected organisms that need large and stable interstitial spaces and high oxygen availability (Descloux et al., 2014;Zhang et al., 2018). ...
Article
The taxonomy-based response pattern of macroinvertebrates to pollution gradient is well established, with tolerant taxa increasing in impacted conditions, while sensitive taxa increase with decreasing deterioration, typical of rural pollution. This study identified rural indicator and sensitive traits of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa by examining their trait distribution pattern in relation to rural pollution. Physicochemical parameters and EPT were sampled seasonally from August 2016 to April 2017. Eight sites were selected and categorised into three site groups. Site group 1 served as the least impacted site group and Site group 2 as the moderately influenced, whereas Site group 3 was the most impacted. Seven traits were selected and categorised into 27 trait modalities. The response of EPT traits to physicochemical parameters was analysed using the simultaneous analysis of the informationcontained in three tables: R (environmental charac-teristics of samples), L (taxa distribution across sam-ples) and Q (species traits) (RLQ) and confirmed with fourth-corner analysis. Three trait attributes, large (10–20 mm), swimming, shredding, streamlined body shape and large body size (≥ 10–20), were consid-ered tolerant signature traits of semi-urban pollution. These trait attributes were associated with the influ-enced Site group 3 and indicated a significant positive affinity with at least one physicochemical indicator of increasing semi-urban pollution (NH4-N, NO3-N, NO2-N, PO4-P, EC, turbidity, temperature and pH). Conversely, small body size (< 10 mm), operculate gills, spherical body shape and a preference for sedi-ments were correlated with the least influenced Site group 1 and were considered sensitive traits of semi-urban disturbance. Overall, this study provided criti-cal insights into EPT responses to disturbance, reveal-ing that semi-urban activities influenced EPT traits differently in the Tsitsa River.
... Trait-based studies based on macroinvertebrates are among the most explored aquatic biota for biomonitoring rivers (Yadamsuren et al., 2020). Anthropogenic pollution has been reported to negatively affect the distribution patterns of macroinvertebrate traits in riverine systems, with traits responding differential along stress gradients (Desrosiers et al., 2019;Ding et al., 2017;Edegbene et al., 2020aEdegbene et al., , 2021Ntloko et al., 2021). However, trait-based studies using the whole macroinvertebrate dataset may be challenging due to the complexity of the dataset and a dearth of autecological information for most macroinvertebrate taxa, particularly Afrotropical species. ...
... These traits were considered rural sensitive traits because they indicated a strong significant negative association with at least one of the physicochemical indicators of semi-urban pollution. Morphological and respiratory traits such as spherical body shape and gills are reported to be sensitive to unstable microhabitats (Ding et al., 2017;Doretto et al., 2018;Magbanua et al., 2010). Likely, elevated sediments and acidity from fertilisers and pesticides use affected organisms that need large and stable interstitial spaces and high oxygen availability (Descloux et al., 2014;Zhang et al., 2018). ...
Article
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The taxonomy-based response pattern of macroinvertebrates to pollution gradient is well established, with tolerant taxa increasing in impacted conditions, while sensitive taxa increase with decreasing deterioration, typical of rural pollution. This study identified rural indicator and sensitive traits of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa by examining their trait distribution pattern in relation to rural pollution. Physicochemical parameters and EPT were sampled seasonally from August 2016 to April 2017. Eight sites were selected and categorised into three site groups. Site group 1 served as the least impacted site group and Site group 2 as the moderately influenced, whereas Site group 3 was the most impacted. Seven traits were selected and categorised into 27 trait modalities. The response of EPT traits to physicochemical parameters was analysed using the simultaneous analysis of the information contained in three tables: R (environmental characteristics of samples), L (taxa distribution across samples) and Q (species traits) (RLQ) and confirmed with fourth-corner analysis. Three trait attributes, large (10–20 mm), swimming, shredding, streamlined body shape and large body size (≥ 10–20), were considered tolerant signature traits of semi-urban pollution. These trait attributes were associated with the influenced Site group 3 and indicated a significant positive affinity with at least one physicochemical indicator of increasing semi-urban pollution (NH4-N, NO3-N, NO2-N, PO4-P, EC, turbidity, temperature and pH). Conversely, small body size (< 10 mm), operculate gills, spherical body shape and a preference for sediments were correlated with the least influenced Site group 1 and were considered sensitive traits of semi-urban disturbance. Overall, this study provided critical insights into EPT responses to disturbance, revealing that semi-urban activities influenced EPT traits differently in the Tsitsa River.
... The elevation ranges might be also considered as an influential variable as the longitudinal gradient of the river is affected by upstream locations and surrounding land use [81]. In short, our results are in line with the findings of previously reported research, which shows that these variables are not only important for taxonomic diversity but also influence functional diversity [20,[82][83][84]. ...
... The limited presence of shredders is not only the case for the CRB and ARB but has also been observed in other tropical rivers [69,96]. The relative distribution of predators is potentially linked with the possible absence of some perturbations, such as deforestation, intensified land-use, the input of nutrients, and organic effluents [4,83]. It may be also related to seasonality, that is, higher predator diversity and abundance had been already reported in Ecuadorian high-altitude streams during the dry season compared to the wet season [97]. ...
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Adequate environmental management in tropical aquatic ecosystems is imperative. Given the lack of knowledge about functional diversity and bioassessment programs, management is missing the needed evidence on pollution and its effect on biodiversity and functional ecology. Therefore, we investigated the composition and distribution of the macroinvertebrate community along two rivers. Specifically, 15 locations were sampled in the Coca and Aguarico Rivers (Ecuado-rian Amazon) and the macroinvertebrates were used to indicate water quality (WQ), expressed as the Biological Monitoring Working Party Colombia (BMWP-Col) classes. Results indicate that elevation , pH, temperature, width, and water depth played an important role in the taxa and functional feeding groups (FFG) composition. The results show that diversity of taxa and FFG were generally scarce but were more abundant in good quality sites. Collector-gathers (CG) were, in general, dominant and were particularly abundant at low WQ and downstream sites. Scrapers (SC) were the second most abundant group, dominating mostly at good WQ and upstream sites. Predators (PR) were homogeneously distributed among the sites, without clear dominance, and their abundance was slightly higher in sites with medium-low WQ and downstream sites. Lastly, both shredders (SH) and collector-filterers (CF) were almost absent and were more abundant in good quality sites. The findings of this research can be used as baseline information in the studied region since a dam was constructed two years after the sampling campaign, which has been operating since. Furthermore , the results can be used to fill the knowledge gaps related to the bioassessments of other similar systems, particularly for a tropical rainforest.
... Similarly, we assigned macroinvertebrate genera according to four trait classifications and 15 categories: respiration (integumentary/ branchial/air), habit (burrowers/climbers/sprawlers/clingers/swimmers), body shape (hydrodynamic/not hydrodynamic), and functional feeding groups (collector-gatherers/collector-filterers/herbivores/ predators/shredders; Ding et al., 2017). We additionally used more comprehensive trait data containing 28 categories for macroinvertebrates (Ding et al., 2017). ...
... Similarly, we assigned macroinvertebrate genera according to four trait classifications and 15 categories: respiration (integumentary/ branchial/air), habit (burrowers/climbers/sprawlers/clingers/swimmers), body shape (hydrodynamic/not hydrodynamic), and functional feeding groups (collector-gatherers/collector-filterers/herbivores/ predators/shredders; Ding et al., 2017). We additionally used more comprehensive trait data containing 28 categories for macroinvertebrates (Ding et al., 2017). Because the patterns of trait heterogeneity across the four regions based on the small (n = 15 categories) and large (n = 28) sets of trait data were highly similar, we therefore present the results based on the small set of trait data. ...
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Metacommunities are structured by a combination of different ecological factors that vary in their importance depending on environmental heterogeneity and species functional equivalence. However, empirical tests of such context-dependence at regional scales are still missing. We investigated associations between deterministic (e.g. environmental filtering and biotic interactions) and stochastic factors (e.g. dispersal related) and metacommunity structure of macroinvertebrates and diatoms across streams in four regions with contrasting levels of environmental and organismal trait heterogeneity. Environmental filtering was most strongly associated with the region that showed moderate environmental heterogeneity and comprised communities with the highest trait heterogeneity. Associations with stochastic factors in the regions were more variable and difficult to predict. Environmental factors and the degree of genus-level association were generally more strongly associated with macroinvertebrates than with diatoms, whereas stochastic factors had consistently lower influence on macroinvertebrates. These results suggest that the degree to which deterministic versus stochastic factors influence aquatic metacommunities depends on environmental and trait heterogeneity. Furthermore, organismal characteristics such as dispersal potential, habitat specialisation and sensitivity to environmental variation can also generate considerable context dependency in metacommunity structure.
... Identifying traitbased indicators of anthropogenic pollution (e.g., agricultural disturbance) is invaluable because it can be used for regular and long-term biomonitoring of river systems when a consistent trait pattern is established. Unlike taxonomic metrics, trait-based indicators can show predictable and stable responses to disturbance across different geographical and temporal scales (Ding et al., 2017). ...
... Trait categories and their attributes were selected on the basis of their mechanistic relationships with agriculturally-induced stressors (e.g., elevated sediments, nutrients, salinisation, and suspended solids and changes in water velocity, pH, and canopy cover). Trait availability and ease of measurement were considered during selection, and previous studies have reported the selected traits to respond markedly to agriculture-related stress (e.g., Poff et al., 2006;Miserendino & Masi, 2010;Ding et al., 2017;McKie et al., 2018;Wang et al., 2019;Scotti et al., 2020). ...
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Agricultural activities impact riverine ecosystem structure, function, and processes. In the Afrotropical regions, research on agricultural effects on macroinvertebrate trait distribution is sparse. In this study, we investigated the spatial and temporal changes in the community structure of macroinvertebrate traits along an agricultural disturbance gradient in an Afrotropical River system. Physicochemical variables were sampled alongside macroinvertebrates at eight sites in the dry (winter and spring) and wet (summer and autumn) periods of 2018–2019. We grouped the sites into four categories using the percentage of agricultural land-use cover within each drainage area. Our results showed that agricultural pollution exhibited varying effects on traits and ecological preferences, with traits such as a predatory lifestyle, medium body-size (>10–20 mm), active swimming, possession of spiracles and haemoglobin, and adult aquatic life stage increasing with the pollution gradient. These traits were positively associated with nutrients (PO4⁺-P, NO2⁺-N, NH4⁺-N and NO3⁺-N), salinity, turbidity and temperature and were deemed tolerant of agricultural pollution. Shredding, crawling, and a preference for macrophytes as food showed strong positive associations with the least disturbed sites and were negatively associated with increasing nutrients, salinity, turbidity and water temperature. As such, these three traits were considered sensitive to agricultural pollution. The identified indicator traits can be used to predict the survival and distribution patterns of organisms under the impact of agriculture-induced stress.
... The average species richness and average density of macroinvertebrates was 31 and 437 ind./m 2 in the 5 DFGs. Compared to other mountain rivers which were not affected by natural disasters in Yunnan Province, the standing stock of macroinvertebrates in DFGs was significantly lower (Ding et al., 2017;Jiang et al., 2009;Wang and Ji, 2012). For example, the average benthic species richness in the upper reaches of Chishui River was 179, and the average density was 3248 ind./m 2 . ...
... The same or different spatial patterns of functional traits can be attributed to environmental changes and trade-offs between different functions (Ding et al., 2017). Different DFGs have different hydrological, topographical, and geomorphic characteristics, so the relative abundance of different rivers at different grades is different. ...
... High shares of grassland, forest and wetland favour EPT taxa, while high shares of cropland and urban area are detrimental. Numerous studies have shown that land use pressures like agriculture and urbanization have a negative impact on water quality at the reach scale (Allan, 2004;Hering et al., 2013;Lorenz & Feld, 2013;Robinson et al., 2014), for example, through reducing oxygen contents (Ding et al., 2017). In contrast, forested catchment has a positive effect. ...
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Woody riparian buffers (hereafter, “woody buffers”) are frequently considered as important to mitigate the effects of stressors on streams and rivers. While several individual studies addressing nutrients, pesticides, water temperature and different biotic components support this conjecture, no study has addressed the effects of woody buffers on riverine biota at country‐wide scales. We used a comprehensive data set from sampling sites on 1082 catchments in France, comprising samples of benthic invertebrates, along with data on river size, physico‐chemistry, hydromorphology, riparian and catchment land use, and woody buffers at sampling sites and upstream. Using Partial Least Square modelling, we delineated the effects of the different environmental variables on two benthic invertebrate metrics, separately for siliceous and calcareous rivers. Overall, models explained 49% (calcareous) and 39% (siliceous) of the variation in benthic invertebrate metrics. Direct effects of woody buffers on benthic invertebrate metrics were marginal, while physico‐chemical conditions and catchment land use explained most of the deviance. Direct and indirect effects of woody buffer together covered up to 6% (upstream scale) plus 2% (local scale) of the explained variability. Synthesis and applications: In this national‐scale study, on 1082 catchments, we investigated the potential of woody buffers to mitigate the effects of catchment‐scale and local‐scale stressors on macroinvertebrate biodiversity. Our results underline that the establishment of woody buffers is not necessarily a sufficient measure to solve the problem of deteriorating riverine macroinvertebrate communities, especially in catchments prone to intense land use. Nevertheless, two main outcomes included that local woody patches are not sufficient and that woody buffers should be established along longer river stretches. Also, accompanying catchment‐scale measures should be promoted to reduce the effects of intense land use and pollution to a level that enables woody buffers to be effective as well.
... Poff et al. [52] and [46] pointed to the fact that the response of a trait to a given indirect stressor(s) may be the cause of an inter-correlation in the response of traits to different stressors. Furthermore, random diffusion or unfinished migration may be attributed to the presence of some of the pollution tolerant trait attributes noted in the LIS relating with the pollution sensitive taxa [53]. ...
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The influence of urbanization on macroinvertebrate traits was explored in forested rivers in the Niger Delta area of Nigeria. Physico-chemical variables were sampled on a monthly basis alongside macroinvertebrates in 20 sites of 11 rivers spanning 2008-2012. Physico-chemical variables were used to classify the 20 sites into three ecological classes, namely: least impacted sites (LIS), moderately impacted sites (MIS) and highly impacted sites (HIS) using principal component analysis. Our results based on RLQ (R = physico-chemical variables, L = macroinvertebrate taxa and Q = macroinvertebrate traits) and fourth-corner analyses revealed that large body size, grazing and hardshell were positively significantly associated with LIS on the RLQ. They were also either negatively correlated with any two of water temperature, nutrients, BOD 5 and flow velocity or positively significantly correlated with increasing DO. Thus, these traits were considered sensitive to urban pollution in forested rivers. Burrowing, predation and pupa aquatic stage, which were positively associated with HIS, were also significantly negatively correlated with increasing DO, and were deemed tolerant of urban pollution in forested rivers. Box plots and a Kruskal-Wallis test revealed that the three sensitive traits were significantly highest at LIS (p < 0.05) except grazing; while the three tolerant traits were significantly highest at MIS (p < 0.05) except burrowing. Overall, this study revealed that urban pollution influences macroinvertebrate traits differently in forested rivers.
... function in the ade4 package (Dray et al., 2014). This method has been used for multi-group communities or whole invertebrate communities (Braaker et al., 2017;de Castro et al., 2018;Ding et al., 2017;Kuzmanovic et al., 2017;Luiza-Andrade et al., 2017;Mocq and Hare, 2018;Murphy et al., 2017;Ossola et al., 2015). Here we applied this method to test for relationships between community morphological traits of a single group of DB (i.e. the tunnellers group) and environmental variables. ...
... Studies elsewhere have also undertaken a trait-based analysis at the family level of taxonomic resolution (e.g. Ding et al. 2017;Forio et al. 2018). ...
Article
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Macroinvertebrate signature traits’ and ecological preferences’ distribution patterns and their responses to urban and agricultural pollution were explored in rivers-draining urban–agricultural catchments within the Niger Delta ecoregion of Nigeria. Physico-chemical variables (water temperature, electrical conductivity, depth, flow velocity, dissolved oxygen, biochemical oxygen demand, nitrates and phosphates) were sampled alongside macroinvertebrates in 17 sites of 11 rivers for a period of five years (2008–2012). Physico-chemically based classification using principal component analysis classify selected sites into least impacted sites (LIS), moderately impacted sites (MIS) and heavily impacted sites (HIS). The results based on RLQ [physico-chemical variables (R), macroinvertebrate taxa (L) and traits and ecological preferences (Q)] and fourth-corner analyses showed that preference for permanent attachment, high sensitivity to oxygen depletion, moderate sensitivity to oxygen depletion and large body size (> 20–40 mm) which were associated with LIS were also positively correlated with DO; thus, they were deemed sensitive to urban–agricultural pollution. Detritus (CPOM) and very small body size (< 5 mm) that were associated with HIS were deemed tolerant to urban–agricultural pollution. Box plots and Kruskal–Wallis test revealed that all sensitive traits and ecological preferences were not significantly different between LIS, MIS and HIS (p > 0.05) except for large body size, while tolerant traits CPOM and very small body size were significantly highest at HIS (p < 0.05). Generally, the study observed differential patterns in the distribution of traits and ecological preferences to urban–agricultural pollution.
... Additionally, we found that FEve was positively correlated with the concentration of phosphorus in the water. Physical and chemical parameters play an important role in functional trait composition and FD (Ding et al. 2017). Reservoir water typically loses phosphorus to the sediment under oligotrophic conditions, and the phytoplankton responds strongly to reduced nutrient concentrations, which is mainly reflected in declining TP concentrations. ...
Article
We assessed the impact of cascaded reservoirs on the phytoplankton’s functional and taxonomic structure. We tested whether functional traits in these communities were selected by the chemical and physical changes that occur in reservoirs downstream in a cascade. Functional diversity and composition were assessed based on eight functional phytoplankton traits and the Simpson taxonomic diversity index. To identify the impact of cascades on functional and taxonomic diversity, we used multiple regression models with environmental variables and variables that indicate cascade interference as predictors and diversity metrics as a response. We fitted simple regression models with physiological and chemical variables in response to the number of reservoirs upstream. Functional and taxonomic diversity and richness decreased with an increasing number of upstream reservoirs. Downstream reservoirs represented by the largest number of upstream reservoirs contained higher proportions of unicellular algae and lower densities of colonial and mucilaginous algae. They also showed higher functional similarity and greater flagellated and unicellular algae density. Both the number of upstream reservoirs and the distance between cascaded reservoirs affected the taxonomic and functional diversity and selection of phytoplankton traits. The increasing distance from upstream dams may help the ecosystem recover, since the larger distance between the dams favored a more uniform traits distribution. These results provide information that is useful for future reservoir management.
... Benthic macroinvertebrate communities perform much of their life cycle in lotic ecosystems and appear to be structured by landscape factors such as land use/catchment vegetation cover, surface geology and geographic basin factors ( Ding et al., 2017 ). However, other studies ( Statzner and Beche, 2010 ;Rezende et al., 2014 ;Vimos-Lojano et al., 2017 ) indicate that local scale variables, e.g. ...
Article
As a function of the dominant vegetation cover, patterns of variation in the structure and composition of both, the aquatic macroinvertebrate communities and their functional feeding groups (FFG) were examined at pristine streams of two high Andean micro-catchments of southern Ecuador. Ten sampling segments were defined in the study streams surrounded by either Tussock grass (TG), Quinua forest (QF) or high mountain forest (HMF). In each segment, environmental and biological samples were collected. Different statistical analyses were implemented for assessing possible relationships between biological and environmental variables. TG and QF streams were found to share many physical and biological characteristics. HMF ecosystems, which are characterised by greater total hardness, water velocity, temperature, pH and nitrite/nitrate concentrations exhibited low values of diversity, richness, relative abundance of non-insects, piercer and parasites. Further, high values of relative abundance of Plecoptera (predators) were observed in HMF, apparently due to higher water velocities and their resistance to these flow conditions. The composition of the macroinvertebrate community showed similarity in TG and QF. It was observed at the three study sites a dominance of organisms generally tolerant to lower availability of oxygen (Chironomidae and non-insect class) and, curiously, to higher concentrations of nutrients. It was found some taxa associated with the presence of organic matter in the sediment because they use allochthonous resources (Phylloecus).
... These regions are ideal intermediate-sized systems (i.e., within a drainage basin) for our study with spatial extent ranging between 168 and 311 km. The study regions located in different climate zones: ITR, QTR and MKR in temperate arid climate, subtropical monsoon climate and tropical monsoon climate, respectively (Wang et al., 2012;Ding et al., 2017;Chen et al., 2019). They are also evidently different in human land use characteristics. ...
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Metacommunity theory provides a useful framework to describe the underlying factors (e.g., environmental and dispersal-related factors) influencing community structure. The strength of these factors may vary depending on the properties of the region studied (e.g., environmental heterogeneity and spatial location) and considered biological groups. Here, we examined environmental and dispersal-related controls of stream macroinvertebrates and diatoms in three regions in China using the distance-decay relationship analysis. We performed analyses for the whole stream network and separately for two stream network locations (headwater and downstream sites) to test the network position hypothesis (NPH), which states that the strength of environmental and dispersal-related controls varies between headwater and downstream communities. Community dissimilarities were significantly related to environmental distances, but not geographical distances. These results suggest that communities are structured strongly by environmental filtering, but weakly by dispersal-related factors such as dispersal limitation. More importantly, we found that, at the whole network scale, environmental control was the highest in the regions with highest environmental heterogeneity. Results further showed that the influence of environmental control was strong in both headwaters and downstream sites, whereas spatial control was generally weak in all sites. This suggests a lack of consistent support for the NPH in our studied stream networks. Moreover, we found that local-scale variables relative to basin-scale variables better explained community dissimilarities for diatoms than for macroinvertebrates. This indicates that diatoms and macroinvertebrates responded to environment at different scales. Collectively, these results suggest that the importance of drivers behind the metacommunity assembly varied among regions with different level of environmental heterogeneity and between organism groups, potentially indicating context dependency among stream systems and taxa.
... This finding is also supported by Baker et al. (2019) research on the long-term elevated EC from 1986 to 2010 in Baltimore-Washington DC. Furthermore, COD concentrations are found to have increased almost two-fold, i.e., from 1.4 to 2.3 mg L −1 in the IUG, and could be attributed to chemical oxidation of cations found in domestic and industrial effluents associated with intense urban development, as demonstrated in a previous study in the Xishuangbanna watershed of the upper Mekong River Basin, China (Ding et al., 2017). Altered channel morphology is reflected in the distinctive decrease in water depth from 20.0 to 14.5 cm, which is associated with increased sediment deposition as a consequence of the high discharge and increased stream load that result from alterations in the stream hydrology . ...
... Changes in community assembly patterns have traditionally been used as surrogates to identify and understand multiple-stressor effects on ecosystems (Lau et al. 2015, Piggott et al. 2015b, Ding et al. 2017. Notably, bacterial communities and activity have proven to be very useful for evaluating stressor-mediated changes in major biogeochemical processes in streams (Romero et al. 2018(Romero et al. , 2019b. ...
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Freshwater ecosystems face many simultaneous pressures due to human activities. Consequently, there has been a rapid loss of freshwater biodiversity and an increase in biomonitoring programs. Our study assessed the potential of benthic stream bacterial communities as indicators of multiple-stressor impacts associated with urbanisation and agricultural intensification. We conducted a fully crossed 4-factor experiment in 64 flow- through mesocosms fed by a pristine montane stream (21 days of colonisation, 21 days of manipulations) and investigated the effects of nutrient enrichment, flow velocity reduction and added fine sediment after 2 and 3 weeks of stressor exposure. We used high-throughput sequencing and metabarcoding techniques (16S rRNA), as well as curated biological databases (METAGENassit, MetaCyc), to identify changes in bacterial relative abundances and predicted metabolic functional profile. Sediment addition and flow velocity reduction were the most pervasive stressors. Both increased α-diversity and had strong, taxon-specific effects on community composition and predicted functions. Sediment and flow velocity also interacted frequently, with 88% of all bacterial response variables showing 2-way interactions and 33% showing 3-way interactions including nutrient enrichment. Changes in relative abundances of common taxa were associated with shifts in dominant predicted functions, which can be extrapolated to underlaying stream-wide mechanisms such as carbon use and bacterial energy production pathways. Observed changes were largely stable over time and occurred after just 2 weeks of exposure, demonstrating that bacterial communities can be well-suited for early detection of multiple stressors. Overall, added sediment and reduced flow velocity impacted both bacterial community structure and predicted function more than nutrient enrichment. In future research and stream management, a holistic approach to studying multiple-stressor impacts should include multiple trophic levels with their functional responses, to enhance our mechanistic understanding of complex stressor effects and promote establishment of more efficient biomonitoring programs.
... Although there are already numerous studies on the ecology of Xishuangbanna, most of them focus on biodiversity conservation [9,10], implication analysis of rubber plantation [11][12][13], carbon-stock [14][15][16], impact of dam construction [17], as well as abiotic risk from environmental degradation in the region [18]. The health status of the aquatic ecosystem in Xishuangbanna was seldom reported. ...
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The Lancang-Mekong River significantly affects the livelihood of residents in the basin as well as the lives of people in other regions of the world in terms of great development potential and its economic and ecological values. In the meanwhile, the river attracts the attention of countries in the basin and the international community because it raises potential for international conflicts. The Lancang-Mekong River leaves China from Xishuangbanna and the ecosystem status in Xishuangbanna constitutes one of the top concerns related to the basin. The study comprehensively evaluates the status of freshwater ecosystem health of the Lancang River in Xishuangbanna for the first time, with reference to aspects of ecosystem vitality, ecosystem services, as well as governance and stakeholders, firstly, linking the ecosystem and the benefits it provides as well as human activities as an organic whole. The methodology used, Freshwater Health Index, is newly developed and constitutes revision of the first attempt of its usage. Basically, the freshwater ecosystem in the studied area and period remains healthy according to the research, and the ecosystem is considered to be capable of providing sufficient services and benefits to meet the economic and societal development demands. Recommendations are proposed for more sustainable local freshwater management and utilization accordingly.
... In the river ecosystem, the functional diversity of macroinvertebrates can better re ect the function of ecosystem than community structure. Many studies showing that substrate type and aquatic vascular plants which affecting the growth and functional group distribution of macroinvertebrate [8][9][10]. ...
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Background: Muling River is the fifth-largest river in Heilongjiang Province, and it is also the main feeding river to the Ussuri River which is the boundary river of China and Russia in Heilongjiang Province northeast of China. Muling River basin located in the south of Sanjiang Plain. Macroinvertebrate samples were collected using a D-frame net and Shannon-Wiener index were calculated in terms of abundance. Results: A total of 158 genera or species macroinvertebrate were collected from the 28 sampling sites and classified into six functional feeding groups including 61 gatherers/collectors, 42 predators, 22 scrapers, 14 shredders, 11 filterers/collectors and 8 omnivores. The correlation and relationship between environmental variables and macroinvertebrate functional feeding groups was explored using Pearson analysis and redundancy analysis. The analysis results displayed that macroinvertebrate functional feeding groups had strong relationships with the environmental variables in the Muling River basin. Conclusions: All FFGs, total abundance and Shannon-Wiener index were not significantly different. Total abundance of macroinvertebrates was higher in summer and biodiversity index was higher in autumn. Environmental factors of natural gradients and nutrition indicator were not significantly different, while others were significantly different.
... These food sources are more readily consumable by freshwater invertebrates than more lignified allochthonous organic matter (Death and Collier, 2010;Thorp and Delong, 1994). Sites with these conditions had higher prevalence of Bivalvia, Gastropoda and some Coleoptera, and thus again a higher prevalence of fully aquatic taxa (Cummins et al., 2005;Ding et al., 2017). ...
Article
Riparian zones ensure freshwater ecosystem processes such as microclimate regulation, organic matter inputs, and fine substrate retention. These processes illustrate the importance of riparian zones for freshwater ecosystem functioning, maintaining biodiversity, and mitigating the effects of anthropogenic pressures on aquatic ecosystems. We aimed to determine the freshwater invertebrate biological traits that are most affected by anthropogenic stressors in the riparian zones of 210 Neotropical savanna headwater streams. We assessed % canopy cover over the streambed, % fine bottom substrate, % leaf pack, substrate heterogeneity, and water temperature. Firstly, we identified bioindicator taxa in response to each local metric gradient. We assessed the functional response, based on biological traits of bioindicators previously selected. We identified 324,015 specimens belonging to 84 freshwater invertebrate taxa. Fifty-one taxa (60%) were bioindicators of anthropogenic stressors. We found three main sets of traits. (1) a set of traits linked to increased disturbance (higher percentage of fine sediments), consisting of organisms with aquatic adult stages, spherical body shape, and long adult life stages. (2) A set of traits linked to lower disturbance (higher substrate heterogeneity), including taxa with short or very short lifespans that live attached to substrates. (3) A set of traits linked to higher water temperature, including organisms with short adult lifespans and lower body flexibility. These patterns suggest that the stressors act as environmental filters and do not act independently on single traits, but rather, selecting sets of biological traits that facilitate taxa surviving and persisting in local environmental conditions. Our results support the development of powerful evaluation tools for environmental managers and decision makers. Because degraded freshwater communities respond in similar ways across large biogeographic areas, these sets of traits can be used for ecological monitoring efforts along other tropical savanna headwaters worldwide.
... Regarding functional divergence, the values obtained for the two vegetation types reflect high niche differentiation, allowing better use of the resources that the plant cover type provides and reduces the levels of competition (Ding et al. 2017). ...
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We evaluated the taxonomic and functional diversity of birds in a rural landscape in the north-eastern Andes of Colombia. We carried out seven field trips and used transects of 300 m, separated from each other by 500 m in the dominant plant cover of the rural landscape. We measured alpha (α) and beta (β) diversity at both the taxonomic and functional levels. We registered 10 orders, 21 families, 56 genera and 63 species of birds. In wooded pasture, we recorded 55 species and a relative abundance of 66% and 44 and 34% for an Andean forest fragment. The species that contributed the most to the dissimilarity between the covers were Zonotrichia capensis , Turdus fuscater , Mecocerculus leucophrys , Atlapetes latinuchus and Crotophaga ani . We identified nine functional types, where G1 was made up of small species with anissodactyl and pamprodactyl legs that were insectivorous, frugivorous and nectarivorous as the best represented. The FEve and FDiv were 0.51 and 0.74, respectively in the Andean forest fragment plant cover and, for the wooded pasture, the FEve was 0.45 and the FDiv was 0.81. Both cover types contributed to the diversity of the rural landscape and the dynamics that existed between them formed a complementary factor that favoured the taxonomic and functional richness of the characterised rural landscape.
... Altered local environmental conditions in or near sampling sites can also explain their lower resilience, because local refuges are important factors in the resilience of lotic ecosystems (Ding et al., 2017;Platt and Connell, 2003). Our results suggest that the urban and industrial stressors in the impacted sites act as selective environmental filters, reducing local biodiversity (Castro et al., 2018;Rahel, 2002). ...
Article
Natural disturbances play important roles in the functioning and structure of lotic ecosystems, especially in small streams. Adaptation to natural disturbances, in the form of resilience, can be affected by anthropogenic disturbances such as urbanization and industrial zones, which in turn can limit stream biodiversity. The aim of this study was to assess the effects of runoff from urban and industrial zones on the resilience of benthic macro-invertebrate assemblages in small streams. For that, we tested the hypothesis that benthic macroinvertebrate assemblages in streams affected by urbanization and industrialization have lower resilience to natural disturbances than those in reference areas. We calculated the recovery proportions of Taxa Richness, Taxa Abundance, Resistant Taxa Richness, Resistant Taxa Abundance, Sensitive Taxa Richness and Sensitive Taxa Abundance. Recovery proportions of freshwater biodiversity were calculated as the target variable values during the dry season divided by the same variable in the previous rainy season. Taxa Richness recovery proportion and Sensitive Taxa Richness recovery proportion were significantly higher (p < 0.01) in the reference sites. Resistant Taxa Richness and Sensitive Taxa Abundance followed the same pattern but were less significant (p < 0.1). These results indicate that streams draining urban and industrial areas have significantly lower resilience to natural disturbances than their counterparts in reference areas. Our results also suggest that both landscape and local environmental conditions play important roles in maintaining naturally resilient lotic ecosystems and biodiversity in the neotropics.
... Functional traits, which may provide insights into the mechanisms driving the distribution of organisms along gradients of stressors, have been proposed as a tool for disentangling the effects of multiple stressors ( Lange et al., 2014). Biological trait-based approaches can predict interactions between community function and environmental gradients and help to understand the functional changes in benthic ecosystems ( Ding et al., 2017;Kenny et al., 2018). ...
... Thus, a measure of diversity based on these functional traits may provide a better understanding of the relationship between biodiversity and ecosystem function (Mouchet et al. 2010;Vaughn 2010;Hooper et al. 2012). Studies demonstrated that agricultural intensification could reduce the functional diversity of different animal communities through the selection of species characterized by a standard set of functional traits (e.g., broader habitat use and diet breadth) (Flynn et al. 2009;Ding et al. 2017;Nevalainen and Luoto 2017). This functional homogenization can generate instability in the trophic structure and severe consequences for the whole ecosystem. ...
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Eutrophication of rivers and streams in agricultural lands is one of the main threats for biodiversity and ecosystem functions. This study was focused on seven subtropical streams where agriculture is the predominant land use. We tested the hypothesis that (i) eutrophication causes a decrease in taxonomic and functional diversity of zooplankton, leading to potential consequences for the ecosystem integrity. Furthermore, given that the temporal variability in the environmental conditions of each stream may influence the species sorting mechanisms, we also hypothesized that (ii) streams with higher temporal environmental variability have greater taxonomic and functional alpha (α) and temporal beta (β t) diversity measures regardless of the trophic state. Thus, we characterized the streams according to their trophic state and analyzed the zooplankton composition, α and β t by using taxonomic and functional perspectives. We found differences in the zooplankton composition between mesotrophic and eutrophic streams. However, eutrophic streams supported similar taxonomic and functional α diversity and similar taxonomic β t diversity to mesotrophic ones. These results were mainly explained by the occurrence of rare species occupying different temporal niches in eutrophic systems. On the contrary, functional β t diversity was lower in the eutro-phic streams, being nestedness the ecological mechanisms underlying the variability in the zooplankton functional groups. Streams with higher temporal environmental variability supported greater α taxonomic diversity. However, the β t diversity metrics showed no correlation with the environmental variability, suggesting that the environmental filters of the studied systems were the overriding determinants of species turnover. Our study suggests that both taxonomic and functional perspectives should be considered to improve our knowledge on the biotic responses to environmental changes. Also, among all metrics analyzed on the zooplankton community, functional β t diversity was the most sensitive indicator of the eutrophication impact.
... These traits are sensitive to environmental changes (including adult flying strength, swimming ability, attachment, armoring, shape, respiration, rheophily, trophic habit, etc.). Trait data for each taxon were obtained from various sources, including information published in the literature [44][45][46]. These characteristics of the individual taxa were determined according to the description of the specimen or classification data. ...
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Spatial biodiversity is a key issue in biogeography for the explorations of biological origin and diversification. However, seldom studies have addressed the temporal changes in spatial patterns of biodiversity. We explored the taxonomic and functional diversities of riverine macroinvertebrates in central China, with the elevational gradient, in different seasons in a normal climate year (i.e., no extreme anomalies in the annual precipitation or average annual temperature). The air temperature and streamflow discharge were decreased monotonically with the increase of elevation both in the dry and wet seasons. In addition, the total nitrogen had no significant change with the increase of elevational gradient in the dry season but showed a monotonically decreasing pattern in the wet season. The total phosphorus showed a monotonically decreasing pattern with the elevational gradient in the dry season but had no significant change in the wet season. The spatial pattern of taxonomic diversity of macroinvertebrates along the elevational gradient showed complex patterns, but the functional diversity had either the unimodal or monotonically decreasing pattern. In addition, the functional diversity with the elevational gradient had similar patterns between the dry and wet seasons. Further analysis of the elevational pattern in different seasons is an important basis for understanding the status quo of functional diversity and formulating countermeasures for biodiversity conservation.
... Land-use related variables, which were considered as indirect factors (usually can alter substrate characteristics, light availability, water quality; Sponseller et al., 2001) affecting organisms, did not showed strong influence on macroinvertebrate communities (only percentage of shrub were retained as significant predictor) in our study. This was Ding et al., (2017), who also found that land use variables had limited influence on benthic community, but disagreed with most of the previous studies (Estévez et al., 2019;Collier and Quinn, 2003). These results might be attributed to the fact that compared to the basin-level land use, macroinvertebrates were more correlated with reach-scale features (Richards et al., 1997), and land-cover in the riparian corridor usually had a stronger influence on habitat variables (Sponseller et al., 2001). ...
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The selection of suitable indicators is the key to the development of multi-metric bioassessment. Here, we examined how taxonomic and functional structures of macroinvertebrate communities responded to the environmental gradients in ten mountainous streams in the Weihe River and Hanjiang River basins, two subtropical biodiversity hotspots in central China. Our main objectives were: 1) to examine whether trait-based metrics performed better than taxonomic compositions in differentiating environmental gradients; 2) to test whether indicators (species and traits) were more efficient than entire communities in discriminating three site groups subjected to different levels of human disturbances. Our results showed that both taxonomic and functional trait compositions, including species-and trait-based indicators, were all sensitive to environmental disturbance. Particularly, the trait-based variables responded more sensitive to human disturbances. Indicator assemblages can be effective surrogates of entire communities in response to environmental changes. Traits-and indicators-based metrics should be considered as useful supplements in the existent bio-monitoring schemes in China. We argued that the combination of taxonomic and functional indicators should be implemented in bioassessment, as they reflect different aspects of environmental changes and anthropogenic disturbances.
... In the present study, we found that tree species identity and mycorrhizal association significantly affected the properties of litter, forest floor, and soil (Table S1), which were in turn related to soil fauna abundance and biomass, as well as soil fauna diversity and evenness. The community composition of soil fauna has been found to be tightly linked to resource availability, vegetation composition, and abiotic environments in various ecosystems (Ding et al., 2017). Previous studies found that leaf litter quality was positively correlated with soil fauna diversity (Frouz et al., 2013;Hobbie et al., 2006), which agree with our findings that both soil taxonomic and functional diversity were higher under tree species that have higher litter quality. ...
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Forest management, including selection of appropriate tree species to mitigate climate change and sustain biodiversity, requires a better understanding of factors that affect the composition of soil fauna communities. These communities are an integral part of the soil ecosystem and play an essential role in forest ecosystem functioning related to carbon and nitrogen cycling. Here, by performing a field study across six common gardens in Denmark, we evaluated the effects of tree species identity and mycorrhizal association (i.e., arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM)) on soil fauna (meso- and macrofauna) taxonomic and functional community composition by using diversity, abundance, and biomass as proxies. We found that (1) tree species identity and mycorrhizal association both showed significant effects on soil fauna communities, but the separation between community characteristics in AM and ECM tree species was not entirely consistent; (2) total soil fauna abundance, biomass, as well as taxonomic and functional diversity were generally significantly higher under AM tree species, as well as lime, with higher litter quality (high N and base cation and low lignin:N ratio); (3) tree species significantly influenced the properties of litter, forest floor, and soil, among which litter and/or forest floor N, P, Ca, and Mg concentrations, soil pH, and soil moisture predominantly affected soil fauna abundance, biomass, and taxonomic and functional diversity. Our results from this multisite common garden experiment provide strong and consistent evidence of positive effects of tree species with higher litter quality on soil fauna communities in general, which helps to better understand the effects of tree species selection on soil biodiversity and its functions related to forest soil carbon sequestration.
... The idea is that, by considering the functional role of species rather than just their specific taxonomy, we can gain insight into how organisms affect and respond to features of their environment (Cadotte et al. 2011, Mouillot et al. 2013. Functional trait analysis has proven useful in plant (Reich et al. 1997), insect (Ding et al. 2017), and microbial ecology (Zak et al. 1994), and has recently expanded into oceanic systems (Micheli and Halpern 2005, Aguilera and Navarrete 2012, Darling et al. 2012, Stuart-Smith et al. 2013, Teixid o et al. 2018). Here, we use an unprecedented 11-yr colonization time series initiated after the 2006 eruption at the 9°50 0 N hydrothermal vent field on the East Pacific Rise, combined with a growing trait database for hydrothermal vent invertebrates (sFDvent; Chapman et al. 2019), to test trait-based successional hypotheses in a new setting with the unusual conditions associated with deep-sea eruptions (i.e., high stress and high nutrients in early succession). ...
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Investigation of communities in extreme environments with unique conditions has the potential to broaden or challenge existing theory as to how biological communities assemble and change through succession. Deep‐sea hydrothermal vent ecosystems have strong, parallel gradients of nutrients and environmental stress, and present unusual conditions in early succession, in that both nutrient availability and stressors are high. We analyzed the succession of the invertebrate community at 9°50’N on the East Pacific Rise for 11 years following an eruption in 2006 in order to test successional theories developed in other ecosystems. We focused on functional traits including body size, external protection, provision of habitat (foundation species), and trophic mode to understand how the unique nutritional and stress conditions influence community composition. In contrast to established theory, large, fast‐growing, structure‐forming organisms colonized rapidly at vents, while small, asexually reproducing organisms were not abundant until later in succession. Species in early succession had high external protection, as expected in the harsh thermal and chemical conditions after the eruption. Changes in traits related to feeding ecology and dispersal potential over succession agreed with expectations from other ecosystems. We also tracked functional diversity metrics over time to see how they compared to species diversity. While species diversity peaked at 8 years post‐eruption, functional diversity was continuing to increase at 11 years. Our results indicate that deep‐sea hydrothermal vents have distinct successional dynamics due to the high stress and high nutrient conditions in early succession. These findings highlight the importance of extending theory to new systems, and considering function to allow comparison between ecosystems with different species and environmental conditions.
... invertebrate communities have helped to disentangle the effects of multiple stressors in streams under different disturbance gradients (Ding et al., 2017;Lange et al., 2014;Schmera et al., 2017). Therefore, biomonitoring programs using the biological water quality indices used here, in addition to FFG, biological traits and functional diversity of aquatic invertebrates, can provide insights for decision making on urbanisation management in tropical Andes. ...
Article
However, knowledge about multiple-stressors effects on urbanised Andean streams is lacking. In southern Ecuador, we assessed how multiple stressors determine the structural (aquatic invertebrate metrics) and functional (organic matter breakdown and delta N of primary consumers) attributes of streams in a densely populated watershed without wastewater treatment and with contrasting land uses. We found that urbanised streams exhibited individual-stressor effects and that stressor interactions were rare. While structural and function attributes responded negatively to urbanisation, ecosystem functioning metrics were influenced most. Stream ecosystem functions were influenced by water-chemistry stressors, whereas aquatic invertebrate metrics were influenced by physical-habitat stressors. We suggest that managers of urbanised streams in the Andes immediately focus on the most important stressors by reducing inputs of inorganic N and P, re-establishing stream flow and substrate heterogeneity, and restoring riparian vegetation instead of attempting to elucidate intricate interactions among stressors. Our result also demonstrate that stream biomonitoring programs would benefit from a combination of structural and functional indicators to assess anthropogenic effects in a multiple-stressors scenario.
... A trait is defined as a characteristic that reflects a species' adaption to its environment (Menezes et al. 2010). Functional traits provide new insights into community responses to environmental stresses and increase our mechanistic understanding of species-environment relationships (Pilière et al. 2015, Ding et al. 2017). ...
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Feeding strategies are traits that reflect the adaptation of a species to environmental conditions. Macroinvertebrates are an important primary consumer in stream food webs, but the abiotic and biotic drivers of functional feeding groups (FFGs), which are categorized based on feeding strategies, require additional clarification. The aim of our study was to quantify the contributions of abiotic factors (water quality and land use at different scales) and biotic factors (important primary producers, such as epilithic diatoms) to the variation of FFGs of macroinvertebrates in the Jinshui River, upper Han River Basin, China, a subtropical mountain river. We conducted campaigns in the Jinshui River during high stream flow (August 2009), low flow (November 2009), and normal flow (April 2010). We performed redundancy analysis and multiple factor analysis to evaluate the relationships among riparian land use at different scales, water quality, the benthic diatom community, and FFGs. We found that water quality, especially the fluoride ion (F⁻), metals (chromium and cadmium), and chemical oxygen demand, significantly correlated with FFGs, and that the benthic diatom community, especially Ceratoneis arcus var. linearis f. recta and Denticula tenuis, explained a high proportion of the variation in FFGs. The benthic diatom community was significantly correlated with water quality, and variations in FFGs were poorly explained by upstream riparian land use at the entire upstream scale and reach scale (2 km upstream). Further, water quality and the benthic diatom community were significantly correlated with riparian land use at the reach scale. Our findings on how the water quality, riparian land use, and diatom community influence FFGs will provide the scientific foundation for biodiversity research of macroinvertebrate FFGs, conservation of the food web, and management of the riparian zone.
... Rao's Q or FDis, are complementary, being useful to apply both of them in a unifying framework. In terms of assessment of anthropogenic disturbance, either metrics based on taxonomic and functional diversity demonstrate response to environmental stressors (Ding et al., 2017;Reynaga and Dos Santos, 2013). Nevertheless, functional approaches result more useful for ecological generalization, and facilitate evaluation of specific stressors which influence the selection of certain traits (McGill et al., 2006;Menezes et al., 2010). ...
Article
This paper proposes the exploration functional diversity of benthic macroinvertebrates to evaluate their response to hydrological and land use stressors in a semi-arid lowland river. We aim to assess dominant functional traits and their sensitivity to environmental drivers, and how functional diversity respond to anthropogenic ecosystem impacts. Environment was evaluated through physical-chemical characterization of water, substrate and hydrological indices. For riparian condition assessment, we applied the QBR index for riparian forest quality and hemeroby index for level of anthropogenic intervention on the landscape. Links between environmental variables (R), taxa distribution (L) and trait composition (Q) were examined with RLQ and combined with fourth-corner analysis. The principal disturbance gradient was related to discharge regulation overlapping with land use represented by hemeroby index. There was also a gradient related to the hydrological regime which alternates seasonal floods with low flow periods. Traits related to reproductive and dispersal strategies were the most influenced by disturbance gradients, both natural and anthropogenic. Functional diversity decrease in sites subject to water abstraction and with higher hemeroby levels. Our findings have been promising in order to the application of functional diversity for biomonitoring in the Dulce River. Hemeroby enables the identification of trending changes between land uses, as well as to identify threat contexts. Furthermore, hemeroby could be useful in diagnostic stages to propose biomonitoring sites, by setting areas with different anthropogenic intervention on the ecosystem.
... For comparison purposes, we used the method proposed by Petchey and Gaston (2002) to calculate FD, i.e., the total branch length of a functional dendrogram. To do this, we used 12 functional traits of aquatic insects that have shown to closely mirror anthropogenic impacts and natural environmental gradients (Ding et al., 2017;Doledec et al., 2011;Li et al., 2019; Table 1). These functional traits included information on life history (e.g., voltinism, development), physiological and basic ecological characteristics (e.g., trophic habits, respiration type), and features associated with resilience or resistance (e.g., body shape, armoring). ...
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Under a global change scenario, human-induced impacts alter multiple facets of river biodiversity (i.e., taxonomic, functional and phylogenetic). Hence, focusing on changes in community assembly and different diversity dimensions along anthropogenic impact gradients is of paramount importance for ecological research. Here, we classified stream sites into near-pristine (NP), moderately impacted (MI) and highly impacted (HI) categories based on a comprehensive anthropogenic impact score for the Hanjiang River Basin (China), and tested for differences in patterns of functional (FD) and phylogenetic diversity (PD). Our study suggests that NP sites showed higher FD and PD than impacted streams (MI and HI), with their communities being phylogenetically overdispersed and mostly shaped by random processes. Anthropogenically impacted sites mostly harbored closely related and functionally similar species, although the degree of clustering varied between NP, MI and HI streams, thereby confirming predictions that human activities contribute to the loss of evolutionary history and functional space in running waters. Importantly, we identified the influence of underlying deterministic mechanisms on the homogenization of both functional and phylogenetic facets of diversity. Similarly, NP sites exhibited the greatest proportion of evolutionarily distinct lineages, suggesting that anthropogenic impacts also threaten phylogenetically unique clades. Overall, this study contributed to a better understanding of multiple diversity patterns in aquatic insect communities by generating new empirical evidence of human-induced degradation of subtropical stream ecosystems in China.
... A general expectation of the authors was for shredders and/or grazer/ scrapers/predators to be replaced by gatherer/collectors in response to deforestation, intensified land-use, inputs of nutrients, and organic effluents (Ding et al., 2017;Mesa, 2014;Miserendino and Pizzolon, 2000). A common problem, especially in tropical regions, is that shredders may still be scarce even if leaf litter is available throughout the year (Li and Dudgeon, 2009;Mesa, 2014), and not always correlated with the amounts of leaf material (Lorion and Kennedy, 2009). ...
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The aim of this study is to generate a first global overview of pressures and methods used to assess the environmental quality of rivers and streams using macroinvertebrates. In total, 314 peer-review studies were reviewed, published in the period 1997 – 2018, from developing economies in Africa, South-Central America, Mexico and Southern Asia. To establish a global perspective, the results from the literature review were compared to other compiled datasets, biomonitoring manuals, environmental surveys and literature reviews from Europe, North America and Australasia. The literature review from the developing economies showed that sampling was most usual during baseflow, using kick- or Surber sampling, with taxonomical identification levels mostly to genus or family. Assessments were most often done using metrics (singular and multimetrics; > 70% of the applications) and were based on community attributes related to richness and dominance (58% of studies), sensitivity (40%), diversity by heterogeneity (32%) and functional traits (25%). Within each category, the most used metrics were the richness and dominance of Ephemeroptera, Plecoptera and Trichoptera (EPT), Biological Monitoring Working Party scoring systems (BMWP/ASPT), Shannon-Wiener diversity and feeding traits. Overall, 92% of the reviewed studies reported that the use of macroinvertebrates, at least in some of their responses, was successful in detecting degradation of environmental quality in the investigated rivers. Given the many similarities in applied methods worldwide, at present, we consider that a global assessment of riverine environmental quality can be feasible by using family level identifications of macroinvertebrate samples. We propose a global common metric (multimetric), comprising three of the most common river assessment metrics from the reviewed literature, but also elsewhere, namely the BMWP/ASPT, Shannon-Wiener diversity and richness of EPT. Recent concerns regarding the global state of nature and consequences for freshwater communities, as reported by the intergovernmental science-policy platform on biodiversity and ecosystem services (IPBES), emphasize the urgent need for such a synthesis.
... Comparable functional divergence suggests that abundance is distributed similarly across the functional-trait space in both land-use communities, indicating equal niche differentiation and competition in forest and pasture communities (Mason et al. 2005). These results are contrary to those of other studies that have documented declines in the components of functional diversity as pressure from changes in land use rises Ding et al. 2017;Wang et al. 2019), suggesting we did not collect data on a temporal or spatial scale that indicated loss of richness or diversity or a reduction of the functional attributes of the macroinvertebrate communities we studied. In addition, there were no significant associations between traits and environmental conditions as indicated by the RLQ analysis, that is consistent with the results of functional diversity. ...
Article
Land use change threatens the ecological integrity of tropical rivers and streams; however, few studies have simultaneously analyzed the taxonomic and functional responses of tropical macroinvertebrates to riparian forest conversion. Here, we used community structure, functional diversity, and stable isotope analyses to assess the impacts of riparian deforestation on macroinvertebrate communities of streams in southern Mexico. Monthly sampling during the dry season was conducted in streams with riparian forest (forest streams), and in streams with pasture dominating the riparian vegetation (pasture streams). Samples were collected for water quality (physical-chemical variables, nutrient concentrations, and total suspended solids), organic matter (leaf litter abundance and algal biomass), and macroinvertebrate abundance and diversity. Higher temperature, conductivity, suspended solids, and chlorophyll a were detected in pasture streams, while nitrate concentrations and leaf litter biomass were greater in forest streams. Macroinvertebrate density was higher in pasture sites, while no differences in taxonomic diversity and richness were found between land uses. Functional evenness was greater in forest streams, while richness and divergence were similar between land uses, despite differences in taxonomic composition. Environmental variables were associated with taxa distribution but not with functional traits, suggesting current conditions still promote redundancy in ecological function. Isotopic analyses indicated consumers in pasture streams were enriched in ¹³C and ¹⁵N relative to forest streams, potentially reflecting the higher algal biomass documented in pasture systems. Isotopic niches were broader and more overlapped in pasture streams, indicating more generalist feeding habits. No significant losses of taxonomic or functional diversity were detected in pasture streams. However, changes in trophic ecology suggest landscape-level processes are altering macroinvertebrate feeding habits in streams. The changes we observed in habitat, water quality, and macroinvertebrate community were related to the removal of the riparian vegetation, suggesting the structure and function of the focal systems would benefit from riparian restoration.
Article
Functional diversity of macrofaunal assemblages can reflect the composition and differences of functional traits, indicating their response to various contaminants, especially heavy metal pollution. We explored the effects of environment variables over gradients of heavy metal pollution on macrofaunal assemblages, using biological traits analysis, generalized linear model (GLM), AZTI marine biotic index (AMBI), and various biodiversity indexes. The RLQ (co-inertia analysis) and fourth-corner approaches were used to investigate the specific response of functional traits to heavy metal pollution. Most sites were environmentally degraded by heavy metal pollution and macrofaunal body size had a miniaturization trend. There was a significant correlation between functional diversity indexes and AMBI. The RLQ and fourth-corner analysis and GLM models showed that heavy metal and natural environmental gradients had a profound effect on functional diversity. The functional divergence and dispersion indexes, along with the abundance of some specific species, were appropriate indexes for heavy metal pollution.
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Anthropogenic salinisation is becoming an increasing global issue for freshwater ecosystems, leading to serious biodiversity loss and ecosystem degradation. While the effect of anthropogenic salinisation on freshwater ecosystems has been intensively studied in recent years, most studies focus on salinisation effects on the individual or single groups of organisms without considering the effect on the ecosystem levels, such as diversity and trophic links. Therefore, we conducted a long-term field survey from May 2009 to August 2016 at 405 sites in northeast China to investigate the effect of a gradient of salinisation on community diversity, functional diversity and trophic links in mountain streams. Samples of water chemistry, periphyton, macroinvertebrates and fish were collected. Our results showed that as anthropogenic salinisation increased, Ca²⁺, Mg²⁺, HCO3⁻ and SO4²⁻ exhibited significant increases (p <0.05). These increased ions caused decreases in taxonomic evenness and biotic integrity, but an increase in the beta diversity for periphyton and macroinvertebrates, and a slight increase in the evenness of fish. The increased salinisation resulted in the extirpation of salt-sensitive taxa and declines in macroinvertebrate functional richness and functional redundancy, which consequently led to simplified trophic links. Our results implied that if salt-tolerant taxa in high salinisation sites were not functionally redundant with less tolerant taxa, alterations of their functional composition probably decrease the stability of ecosystem functions. Overall, our study suggests that the ongoing anthropogenic salinisation is posing serious threats to biodiversity and trophic links in river ecosystems, and should be considered in future river restoration and biodiversity conservation.
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Improved knowledge of biological diversity patterns associated with elevation and their driving factors is indispensable for developing ecological theories. However, the results for the elevational distribution patterns of soil fauna are not consistent due to differing climates and vegetation. Here, we present a comprehensive analysis of soil macroinvertebrate composition and structure among different forests at three elevations on the eastern Tibetan Plateau, China. A total of 16,559 individuals belonging to 24 orders and 100 families were collected, and the macroinvertebrate individual abundance, family richness, and diversity apparently increased with increasing elevation. Moreover, remarkable seasonal dynamics were observed for both the composition and functional structure of soil macroinvertebrates among forest types and were inconsistently affected by different environmental factors. The structural equation model suggested that elevation indirectly affected soil macroinvertebrate abundance by modulating climate (e.g., temperature) and soil quality (e.g., soil organic carbon and total nitrogen). Additionally, although vegetation had minor direct effects on soil macroinvertebrate abundance, it might indirectly influence soil macroinvertebrate abundance by regulating plant litter input. Our results indicate that temperature and soil nutrients are critical factors of soil macroinvertebrate elevational distributions and highlight the importance of plant litter input in determining the composition and structure of soil macroinvertebrates at different elevations.
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This study is based on biological trait analysis (BTA), which provides a link between the distribution and biological characteristics of species. The paper investigates differences in the structure and functional diversity of benthic fauna in terms of seven biological traits (mobility, habitat, feeding type, habitat modification, body form, body size and feeding apparatus) in nine Baltic coastal lakes whose salinity ranged from 0.1 to 7.3 PSU. Mobile organisms were more common in lakes with higher salinity, while sessile and semi-mobile species preferred low-salinity or freshwater environments. There were also noticeable differences connected with feeding type: collectors and scrapers were more common in brackish lakes, and collectors were significantly dominant in freshwater and transitional ones. This indicates that Baltic coastal lakes are inhabited by similar species of benthic fauna, but that certain biological traits occur with different frequencies. We therefore identified features that may affect the functioning of coastal lakes with a relatively narrow salinity gradient (0.1–7.3 PSU). It seems to confirm the possibility of using BTA methods to determine key characteristics that are helpful for understanding the differences between aquatic ecosystems. The results may provide a basis for further research on changes in the functional diversity of lakes along the southern coast of the Baltic Sea, particularly in view of climate change, given their being small, shallow and less resilient lakes.
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Understanding the contribution of rare biological groups to functional diversity, especially in systems impacted by land use, is fundamental to comprehend the biodiversity patterns and establish more efficient conservation strategies. This study mainly aimed to identify the contribution of rare aquatic insects to functional diversity in environments of the forest, logging, and pasture. A total of 7517 immature insects were collected from 32 streams in the Amazon forest: the rare genera were classified by a rarity index and represented just over 2% of the sampled individuals. The results showed that there was a difference in the composition of aquatic insects among the land use. In streams of logging, there was greater functional dispersion and the rare genera presented functional characteristics sensitive to water temperature increase and channel width. The contribution of rare and common insects in the forest, pasture and areas of logging was equal. This study highlights the necessity for long-term studies since the loss or replacement of rare taxa is, among other factors, driven by environmental filters, which tend to simplify communities and reduce the functionality of the system.
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Identifying the underlying mechanisms that explain the spatial variation of stream macroinvertebrate assemblages is crucial for the protection of species diversity. Consequently, questions regarding how much variance in macroinvertebrate community structure is related to spatial dispersal and local environmental factors, and which environmental variables are the key drivers have broad research and management implications. Based on data from 22 stream sites within the Qinjiang River watershed, Guangxi, China, we examined the variation in macro invertebrate community structure attributable to local environmental factors (i.e. stream physical habitat and water chemistry) vs. spatial dispersal factors (i.e. overland and watercourse spatial eigenvectors among sampling sites) using variation partitioning procedures. Overall, we found that stream macro invertebrates are influenced both by local environmental factors and spatial dispersal factors. The most important environmental factors structuring macro invertebrate assemblages were current velocity, dissolved oxygen, conductivity, total phosphorus, and physical habitat quality. Both overland and watercourse dispersal pathways had a similar influence on macroinvertebrate assemblages. These results demonstrate that stream macroinvertebrates within the studied landscape are constrained by local environmental conditions and dispersal factors, and hence comply with the niche-based species sorting hypo thesis in the context of metacommunity ecology.
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Drastic biodiversity declines have raised concerns about the deterioration of ecosystem functions and have motivated much recent research on the relationship between species diversity and ecosystem functioning. A func-tional trait framework has been proposed to improve the mechanistic understanding of this relationship, but this has rarely been tested for organ-isms other than plants. We analysed eight datasets, including five animal groups, to examine how well a trait-based approach, compared with a more traditional taxonomic approach, predicts seven ecosystem functions below-and above-ground. Trait-based indices consistently provided greater explanatory power than species richness or abundance. The frequency distri-butions of single or multiple traits in the community were the best predictors of ecosystem functioning. This implies that the ecosystem functions we investigated were underpinned by the combination of trait identities (i.e. single-trait indices) and trait complementarity (i.e. multi-trait indices) in the communities. Our study provides new insights into the general mechan-isms that link biodiversity to ecosystem functioning in natural animal communities and suggests that the observed responses were due to the iden-tity and dominance patterns of the trait composition rather than the number or abundance of species per se.
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Climate warming in (sub)arctic regions is expected to increase freshwater fish overwinter survival and dispersal, potentially with strong implications for macroinvertebrate assemblage composition and ecosystem processes. Several studies worldwide have shown large effects of top predators (usually fish) on macroinvertebrates in streams. However, the influence of top predators on trophic diversity, the range of food resources exploited and trophic niche redundancy is less well studied, particularly in cold regions.Using stable isotopes (13C and 15N) and fish gut content analysis, we investigated the effect of top predators on macroinvertebrate food webs in streams in Greenland by comparing adjacent sites with and without fish (Gasterosteus aculeatus).Food-web metrics estimated from stable isotope data showed that the presence of fish reduced the diversity of food sources exploited by macroinvertebrates as well as their trophic diversity. In addition, fish presence increased packing and trophic redundancy of macroinvertebrate taxa in the food web, possibly due to behavioural changes in foraging activity. Furthermore, predatory macroinvertebrate taxa were unable to attain the trophic position of fish so that food webs were one trophic level longer in streams with fish. Focusing on macroinvertebrate food webs alone, predatory macroinvertebrates did not change their trophic position in the presence of fish.Filter feeders dominated the macroinvertebrate assemblage when fish were present, while the relative abundance of collector-gatherers was marginally higher in the fishless streams. This pattern was consistent with stronger selectivity for collector-gatherers by fish.Climate-driven fish colonisation in currently fishless Greenland streams may induce a shift in macroinvertebrate food webs, with a reduction in both trophic diversity and the variety of food sources consumed. To some extent, this might counteract a change towards a broader use of food resources by macroinvertebrates that might otherwise be expected at higher temperatures. In addition, a shift in the macroinvertebrate assemblage towards dominance of filter feeders can be expected to promote an increase in periphyton biomass in streams with fish.
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Functional trait diversity provides a powerful means of addressing ecology's persistent questions, through its dual role as an indicator of mechanisms driving differences in species composition between communities and as a predictor of ecosystem-level processes. Functional traits provide a means of testing mechanisms behind species turnover between communities because environmental heterogeneity, competition and disturbance influence species fitness via their traits. Functional traits also provide a link between species and multiple ecosystem-level processes, such as primary productivity, nutrient fluxes and resilience, since species influence these processes via their traits. This special issue demonstrates that functional diversity offers a practical means of investigating ecology's persistent questions.
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BRIDGES BRIDGES is a recurring feature of J-NABS intended to provide a forum for the interchange of ideas and information between basic and applied researchers in benthic science. Articles in this series will focus on topical research areas and linkages between basic and applied aspects of research, monitoring, policy, and education. Readers Abstract. Selection of reference sites is a critical component in the process of developing and applying biological indicators of ecological condition. Some evidence suggests that despite its importance the rules by which reference sites are selected have not always been evaluated critically to assure that the sites represent least-disturbed conditions. We present a comparison of physical and chemical disturbance measures and biotic indices at handpicked reference sites provided by resource agencies and at sites selected by a probability design from a 12-state survey of western streams and rivers. In most cases, the distributions of disturbance measures and biotic index scores were essentially the same for both types of sites; that is, only a subset of the handpicked reference sites represented least-disturbed conditions. We recommend that all agencies that use reference sites critically review those sites with a set of explicit criteria, using field-collected data as well as mapped information.
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The impacts of watershed urbanization on streams have been studied worldwide, but are rare in China. We examined relationships among watershed land uses and stream physicochemical and biological attributes, impacts of urbanization on overall stream conditions, and the response pattern of macroinvertebrate assemblage metrics to the percent of impervious area (PIA) of watersheds in the middle section of the Qiantang River, Zhejiang Province, China. Environmental variables and benthic macroinvertebrates of 60 stream sites with varied levels of watershed urban land use were sampled in April, 2010. Spearman correlation analysis showed watershed urbanization levels significantly correlated with increased stream depth, width, and values of conductivity, total nitrogen, ammonia, phosphate, calcium, magnesium, and chemical oxygen demand for the study streams. There was significant difference in total taxa richness, Empheroptera, Plecoptera, and Trichoptera (EPT) taxa richness, and Diptera taxa richness, percentages of individual abundances of EPT, Chironomidae, shredders, filterers, and scrapers, and Shannon–Wiener diversity index between reference streams and urban impacted streams. In contrast, percentages of individual abundances for collectors, oligochaeta, and tolerant taxa, and biotic index were significantly higher in urban impacted than reference streams. All the above metrics were significantly correlated with PIA. The response patterns of total taxa richness, EPT taxa richness, and Shannon–Wiener diversity index followed a drastic decrease at thresholds of 3.6, 3.7, and 5.5% of PIA, respectively. Our findings indicate that stream benthic macroinvertebrate metrics are effective indicators of impacts of watershed urban development, and the PIA-imperviousness thresholds we identified could potentially be used for setting benchmarks for watershed development planning and for prioritizing high valued stream systems for protection and rehabilitation.
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Functional ecology aims at determining the relationships between species traits and environmental variables in order to better understand biological processes in ecosystems. From a methodological point of view, this biological objective calls for a method linking three data matrix tables: a table L with abundance or presence-absence values for species at a series of sites, a table R with variables describing the environmental conditions of the sites, and a table Q containing traits (e.g., morphological or behavioral attributes) of the species. Ten years ago, the fourth-corner method was proposed to measure and test the relationships between species traits and environmental variables using tables R, L, and Q simultaneously. In practice, this method is rarely used. The major reasons for this lack of interest are the restriction of the original method and program to presence-absence data in L and to the analysis of a single trait and a single environmental variable at a time. Moreover, ecologists often have problems in choosing a permutation model among the four originally proposed. In this paper, we revisit the fourth-corner method and propose improvements to the original approach. First, we present an extension to measure the link between species traits and environmental variables when the ecological community is described by abundance data. A new multivariate fourth-corner statistic is also proposed. Then, using numerical simulations, we discuss and evaluate the existing testing procedures. A new two-step testing procedure is presented. We hope that these elements will help ecologists use the best possible methodology to analyze this type of ecological problem.
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The use of species traits to characterize the functional composition of benthic invertebrate communities has become well established in the ecological literature. This approach holds much potential for predicting changes of both species and species assemblages along environmental gradients in terms of traits that are sensitive to local environmental conditions. Further, in the burgeoning field of biomonitoring, a functional approach provides a predictive basis for understanding community-level responses along gradients of environmental alteration caused by humans. Despite much progress in recent years, the full potential of the functional traits-based approach is currently limited by several factors, both conceptual and methodological. Most notably, we lack adequate understanding of how individual traits are intercorrelated and how this lack of independence among traits reflects phylogenetic (evolutionary) constraint. A better understanding is needed if we are to make the transition from a largely univariate approach that considers single-trait responses along single environmental gradients to a multivariate one that more realistically accounts for the responses of many traits across multiple environmental gradients characteristic of most human-dominated landscapes. Our primary objective in this paper is to explore the issue of inter-trait correlations for lotic insects and to identify opportunities and challenges for advancing the theory and application of traits-based approaches in stream community ecology. We created a new database on species-trait composition of North American lotic insects. Using published accounts and expert opinion, we collected information on 20 species traits (in 59 trait states) that fell into 4 broad categories: life-history, morphological, mobility, and ecological. First, we demonstrate the importance of considering how the linkage of specific trait states within a taxon is critical to developing a more-robust traits-based community ecology. Second, we examine the statistical correlations among traits and trait states for the 311 taxa to identify trait syndromes and specify which traits provide unique (uncorrelated) information that can be used to guide trait selection in ecological studies. Third, we examine the evolutionary associations among traits by mapping trait states onto a phylogentic tree derived from morphological and molecular analyses and classifications from the literature. We examine the evolutionary lability of individual traits by assessing the extent to which they are unconstrained by phylogenic relationships across the taxa. By focusing on the lability of traits within lotic genera of Ephemeroptera, Plecoptera, and Trichoptera, taxa often used as water-quality indicators, we show how a traits-based approach can allow a priori expectations of the differential response of these taxa to specific environmental gradients. We conclude with some ideas about how specific trait linkages, statistical correlations among traits, and evolutionary lability of traits can be used in combination with a mechanistic understanding of trait response along environmental gradients to select robust traits useful for a more predictive community ecology. We indicate how these new insights can direct the research in statistical modeling that is necessary to achieve the full potential of models that can predict how multiple traits will respond along multiple environmental gradients.
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The impact of fish predation on epibenthic organisms at different trophic levels was studied in a series of replicated experimental outdoor channels fed by a boreal forest stream (Québec, Canada). Brook trout (Salvelinus fontinalis) were introduced into five of 10 channels according to a randomized block experimental design. Periphyton biomass (expressed as total chlorophyll a and total organic matter) and macroinvertebrate biomass were measured four times during the summer. The biomass of small insects such as Chironomidae was always higher in the presence than in the absence of fish, while the biomass of larger invertebrates such as Baetis (Ephemeroptera) and Psychoglypha subborealis (Trichoptera) was reduced in the presence of fish. Periphyton biomass was significantly greater in channels with fish on the first sampling date after fish introduction but not at later dates. Complementary cage experiments, involving both the inclusion and exclusion of selected invertebrates from periphyton-covered surfaces, demonstrated that the presence of Baetis can reduce the periphytic biomass, while the presence of P. subborealis can reduce the biomass of Chironomidae. Overall, these results suggest that size-selective predation by brook trout can cause profound changes in the structure of epibenthic communities at primary as well as secondary trophic levels.
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1. The species composition of stream fish assemblages changes across the longitudinal fluvial gradient of large river basins. These changes may reflect both zonation in species distributions and environmental filtering of fish traits as stream environments change from the uplands to the lowlands of large catchments. Previous research has shown that taxonomic diversity generally increases in larger, lowland streams, and the River Continuum Concept, the River Habitat Template and other frameworks have provided expectations for what functional groups of fishes should predominate in certain stream types. However, studies addressing the functional trait composition of fish assemblages across large regions are lacking, particularly in tropical river basins.
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The use of species traits in basic and applied ecology is expanding rapidly because trait-based approaches hold the promise to increase our mechanistic understanding of biological responses. Such understanding could transform descriptive field studies in community ecology into predictive studies. Currently, however, trait-based approaches often fail to reflect species–environment relationships adequately. The difficulties have been perceived mainly as methodological, but we suggest that the problem is more profound and touches on the fundamentals of ecology and evolution. Selection pressures do not act independently on single traits, but rather, on species whose success in a particular environment is controlled by many interacting traits. Therefore, the adaptive value of a particular trait may differ across species, depending on the other traits possessed by the species and the constraints of its body plan. Because of this context-dependence, trait-based approaches should take into account the way combinations of traits interact and are constrained within a species. We present a new framework in which trade-offs and other interactions between biological traits are taken as a starting point from which to develop a bette