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Understanding biotic assemblage variations resulting from water diversions and other pressures is critical for aquatic ecosystem conservation, but hampered by limited research. Mechanisms driving macroinvertebrate assemblages were determined across five lakes along China's South-to-North Water Diversion Project, an over 900-km water transfer system connecting four river basins. We assessed macroinvertebrate patterns from 59 sites in relation to water quality, climatic, spatial, and hydrologic factors. Macroinvertebrate density, biomass, and species richness increased from upriver to downriver lakes, and were higher during the water transfer period than in the non-water transfer period. Non-native species including Nephtys sp., Paranthura japonica, Potamillacf acuminata, Capitekkidae spp. and Novaculina chinensis, were distributed along the entire study system, some become dominant in upriver lakes. High species turnover occurred in two upriver lakes. Hydrology and water quality are critical factors in shaping these macroinvertebrate patterns. Hydrological disturbance by water transfer boosted macroinvertebrate abundance during the water transfer period while facilitated non-native species dispersals and increased biotic homogenization. This study indicates the need for: 1) an effective ecosystem monitoring system; 2) unified system management standards; 3) external pollution controls; and 4) limiting the dispersal of non-native species.

Environmental filtering and spatial processes have been associated with variation in ecological communities and biodiversity; however, their relative importance on multiple dimensions of beta diversity has not been fully explored in montane streams. Here, we examined the relative contribution of local, catchment and climate environmental variables and spatial factors to variation in three dimensions of macroinvertebrate beta diversity in the upper Han River Basin. Taxonomic, functional, and phylogenetic beta diversities and their respective turnover and nestedness components were calculated for macroinvertebrate assemblages sampled in a total of 130 stream sites across a large mountainous landscape. We investigated the correlations between beta diversity facets using MSR-Mantel procedure and then examined the relative influence of each set of ecological factors through redundancy analysis and variance partitioning. Our results revealed relatively low spatial congruence among beta diversity dimensions, indicating these diversity dimensions are independent measures which offer complementary information of community assembly. Beta diversity dimensions and components were best explained by spatial and local environmental factors, whereas the large-scale catchment and climate factors appeared less influential. Moreover, spatial and environmental factors generally exerted different controls on beta diversity depending on the dimensions under consideration. Taxonomic and phylogenetic beta diversities were more strongly determined by spatial factors via dispersal limitation, while functional beta diversity was mainly associated to local environments through habitat filtering. Our results challenge the perspective that using one diversity facet as a surrogate for others is enough, and highlight the need to integrate multiple diversity dimensions in metacommunity and biodiversity research.

Identifying seasonal shifts in community assembly for multiple biological groups is important to help enhance our understanding of their ecological dynamics. However, such knowledge on lotic assemblages is still limited. In this study, we used biological traits and functional diversity indices in association with null model analyses to detect seasonal shifts in the community assembly mechanisms of lotic macroinvertebrates and diatoms in an unregulated subtropical river in China. We found that functional composition and functional diversity (FRic, FEve, FDis, MNN, and SDNN) showed seasonal variation for macroinvertebrate and diatom assemblages. Null models suggested that environmental filtering, competitive exclusion, and neutral process were all important community assembly mechanisms for both biological groups. However, environmental filtering had a stronger effect on spring macroinvertebrate assemblages than autumn assemblages, but the effect on diatom assemblages was the same in both seasons. Moreover, macroinvertebrate and diatom assemblages were shaped by different environmental factors. Macroinvertebrates were filtered mainly by substrate types, velocity, and CODMn, while diatoms were mainly shaped by altitude, substrate types, and water quality. Therefore, our study showed (a) that different biological assemblages in a river system presented similarities and differences in community assembly mechanisms, (b) that multiple processes play important roles in maintaining benthic community structure, and (c) that these patterns and underlying mechanisms are seasonally variable. Thus, we highlight the importance of exploring the community assembly mechanisms of multiple biological groups, especially in different seasons, as this is crucial to improve the understanding of river community changes and their responses to environmental degradation., (a) Null models suggested that environmental filtering, competitive exclusion, and neutral process were all important community assembly mechanisms for both biological groups. (b) Different biological assemblages in a river system presented similarities and differences in assembly mechanisms. (c) Patterns and underlying mechanisms are seasonally variable.

Highlights •We examined how eutrophication affects macroinvertebrate biodiversity in 33 lakes. •Three facets of alpha diversity declined with increasing of eutrophication. •Functional diversity indices performed best in portraying anthropogenic disturbances. •Environmental filtering dominated over spatial factors in explaining multifaceted alpha diversity. Abstract The accelerated eutrophication of freshwater lakes has become an environmental problem worldwide. Increasing numbers of studies highlight the need to incorporate functional and phylogenetic information of species into bioassessment programms, but it is still poorly understood how eutrophication affects multiple diversity facets of freshwater communities. Here, we assessed the responses of taxonomic, phylogenetic and functional diversity of benthic macroinvertebrates to water eutrophication in 33 lakes in the Yangtze River floodplain in China. Our results showed that macroinvertebrate assemblage structure was significantly different among four lake groups (river-connected, macrophyte-dominated, macrophyte-algae transition, and algae-dominated). Three taxonomic, two phylogenetic and two functional diversity indices were significantly different among the lake groups. Except for the increasing trend of Lambda+, these metrics showed a clear decreasing trend with increasing levels of eutrophication, with highest values detected in river-connected and macrophyte-dominated lakes, followed by macrophyte-algae transition lakes and algal-dominated lakes. Although differing in the number and identity of key environmental and spatial variables among the explanatory models of different diversity indices, environmental factors (eutrophication-related water quality variables) played more important role than spatial factors in structuring all three facets of alpha diversity. The predominant role of environmental filtering can be attributed to the strong eutrophication gradient across the studied lakes. Among the three diversity facets, functional diversity indices performed best in portraying anthropogenic disturbances, with variations in these indices being solely explained by environmental factors. Spatial factors were mostly weak or negligible in accounting for the variation in functional diversity indices, implying that trait-based indices are robust in portraying anthropogenic eutrophication in floodplain lakes. However, variation in some taxonomic and phylogenetic diversity indices were also affected by spatial factors, indicating that conservation practitioners and environmental managers should use these metrics with caution when providing solutions for addressing eutrophication in floodplain lakes.

Although environmental filtering and spatial structuring are commonly regarded as two key factors shaping community dynamics, their relative contribution remains unknown for numerous aquatic ecosystems, particularly highly dynamic floodplain lakes. This issue is here addressed by examining the seasonal metacommunity dynamics of freshwater fishes in Lake Dongting, a large subtropical lake of the middle Chang-Jiang basin in southern China. Physicochemical variables and fish assemblages were recorded at 20 sampling sites during the wet, normal, and dry seasons. Distance-based redundancy analysis and associated variation partitioning were used to examine the relative role of environmental variables and spatial factors in fish community assembly in each season. Analysis results demonstrated that the relative contribution of environmental filtering and spatial structuring varied depending on environmental features and the extent of hydrological connectivity in different seasons. Intensified physicochemical parameters in the dry season convinced the enhanced environmental filtering, whereas high hydrological connectivity in the wet season favored the stronger spatial process. Specifically, the community assembly processes were temporally dynamic; spatial structuring (or mass effects), resulting from excessively high dispersal rates, was dominant during the flooding season, and environmental filtering was stronger than spatial structuring (or dispersal limitation) during the non-flooding season. These findings highlight the importance of conserving local habitats of Lake Dongting during the dry and normal seasons, and maintaining of the flood pulse of the lake and its natural variability during the wet season. Apparently, the construction of a water-level regulation project at the Chenglingji Channel, the outlet watercourse of Lake Dongting, is not supported because it will change the flood pulse of this lake and thus impact habitat heterogeneity or variability.

Conversion of forests to urban land-use in the processes of urbanization is one of the major causes of biotic homogenization (i.e., decline in beta diversity) in freshwater ecosystems, threating ecosystem functioning and services. However, empirical studies exploring urban land-use shaping patterns of taxonomic and functional beta diversities and their components in subtropical urban rivers are limited. Here, by leveraging data for 43 sampling sites from urban and forest rivers in Shenzhen, a megacity showing rapid urbanization, we determined the spatio-temporal dynamics and associated drivers of taxonomic and functional beta diversities of river macroinvertebrates. Our results showed that, from the forest to urban rivers, taxonomic beta diversity (wet: 32.9%; dry: 17.1%) declined more significantly than functional beta diversity (wet: 17.4%; dry: 9.5%) in different seasons. We further found that these compositional changes were largely driven by decreased roles of species/traits replacement. Although replacement was also dominant for taxonomic beta diversity (60.4%-68.4%) in two sets of rivers, richness difference contributed more to functional beta diversity in the urban river (52.6%-60.5%). Both deterministic and stochastic processes simultaneously affected beta diversity, with stochastic processes being more important in the urban (3.0-19.0%) than forest rivers (0.0%-3.0%). Besides, db-RDA and variation partitioning results showed that local-scale environmental variables explained considerably large fractions of variation in beta diversity. We hence recommended that biodiversity conservation should focus on improving and restoring local environmental conditions. Despite no significant seasonal differences in beta diversity were detected in this study, we found that the roles of deterministic (i.e., local-scale and land-use variables) and stochastic processes varied considerately across seasons. This result highlights the viewpoint that urban river biodiversity monitoring should go beyond one-season snapshot surveys. As the ongoing trend of urbanization in developing countries, the findings of this study are relevant in guiding urban river environmental monitoring, biodiversity conservation and land-use planning.

Deterministic and stochastic processes are two major factors shaping community dynamics, but their relative importance remains unknown for many aquatic systems, including those in the high‐elevation Qinghai–Tibet Plateau. Here, we explored the causes of multidimensional beta diversity patterns (i.e., taxonomic, functional, and phylogenetic) of a macroinvertebrate metacommunity in this large aquatic system by using multiple approaches (i.e., null models, phylogenetic signal testing, and ordination‐based approaches). To obtain insights into community assembly mechanisms, we also analyzed beta diversity in two deconstructed sub‐metacommunities (e.g., different tributaries and the main lake body). We found that most functional traits showed significant phylogenetic signals, indicating that the functional traits were profoundly influenced by evolutionary history. The null models showed randomness of functional and phylogenetic beta diversities for the whole basin and its tributaries, confirming the importance of stochasticity over deterministic processes in controlling community structure. However, both phylogenetic and functional community structures were clustered in the Qinghai Lake, probably reflecting the importance of environmental filtering. Ordination‐based approaches also revealed that both environmental factors and spatial processes accounted for variation in taxonomic, functional, and phylogenetic beta diversity. More specifically, environmental filtering was more important than spatial processes for the functional dimension, but the opposite was true for the taxonomic and phylogenetic dimensions. The paleogeographic history of the Qinghai Lake basin may have contributed substantially to the prevalence of stochastic processes. Overall, this study provides a better understanding of ecological patterns and assembly mechanisms of macroinvertebrate communities across this poorly known high‐elevation aquatic system that is highly sensitive to climate warming.

Sediment dredging is a controversial technology for lake eutrophication control. A lengthy and holistic assessment is important to understand the effects of a dredging project on a lake ecosystem. In this study, a dredging project was followed for 5 years. To understand the variations of lake ecosystems before, during and after the project, water quality, phytoplankton, zooplankton and benthic animal biomass were monitored; Four subindicators, including eco-exergy (Ex), structural eco-exergy (Exst), buffer capacity of total phosphorus for phytoplankton (β(TP)(phyto)) and trophic level index (TLI) were calculated and developed to an integrated ecosystem health indicator (EHI). The monitoring results showed that the dredging project caused many short-term positive effects such as decreased total nitrogen, total phosphorus, permanganate index and phytoplankton biomass throughout the entire lake water, increased Secchi disk depth in the whole lake and increased benthonic animal biomass in the nondredged regions. However, these positive effects disappeared overtime. Water chemistry and biomass returned to the initial state before dredging. EHI showed that the dredging project caused negative effects on the lake health in the dredged region at first. Subsequently, the health status of the entire lake, including the dredged and nondredged regions, improved until 1–2 years after the project finished. Because of the lack of other timely ecological restoration measures, the lake gradually returned to its initial health status. However, the health status in the dredged regions was only slightly better than before dredging and often worse than that of the nondredged regions. Our study suggested that dredging projects may only cause short-term positive effects on lake ecosystem health. The external interception and dredging ratio were important. A dredging project should be combined with other ecological lake restoration measures when the project has caused positive effects in a lake.

Functional trait-based measures can reflect local environmental conditions and are claimed as promising approaches for environmental monitoring and assessment programs. The chironomid larvae are a diverse and ecologically important group of benthic macroinvertebrates and have a set of functional traits that can be used to assess environmental quality of freshwater ecosystems. However, little is known regarding the relationships between chironomid functional structure and human disturbances, especially at a fine taxonomic resolution. Here, we compared the responses of functional traits and traditional taxonomic measures of chironomid assemblages to eutrophication in the Yangtze floodplain lakes. We found that functional composition showed higher sensitivity and robustness in discriminating the extents of eutrophication than taxonomic composition. Specifically, about half of functional categories examined significantly differed among the lake groups, while only two taxonomical measures (the abundance of Tanytarsini and Polypedilum) are suitable for assessing environmental quality of floodplain lakes. The macrophytic lakes showed higher abundance of scrapers, the small body size and oligotrphic individuals. Whereas the algal lakes were associated with high abundance of eutrophic/hypertrophic chironomids and those with haemoglobin. Chironomid assemblages showed significant differences among four lake groups for both trait-based and taxonomy-based variations, but with larger differences for trait-based groups. The distance-based redundancy analysis (dbRDA) indicated that taxonomic and functional assemblage structures were explained primarily by similar water quality variables (chlorophyll a, transparency and TN), but more functional variation (24.6%) was explained by environmental factors than taxonomic variation (10.9%) in chironomid assemblages. Our results indicated that chironomid trait-based approaches were more sensitive and robust to water quality gradients than taxonomy-based approaches. Therefore, we argued that the chironomid functional traits deserve considerations for biomonitoring programs in the lakes we studied and other freshwater lakes and aquatic ecosystems.

Human-mediated introductions of exotic species and extirpations of native species have modified the composition of biotic communities throughout the world, but the consequences of introductions and extirpations on local phylogenetic diversity (alpha-diversity) and on phylogenetic distinctiveness between sites (beta-diversity) remains poorly investigated. Here we analyze the long-term impacts of extirpations and invasions on both phylogenetic and taxonomic alpha and beta diversity of fish assemblages in Chinese isolated lakes. Data of fish assemblages in 15 lakes were grouped into three periods spanning the last 75 years: historical, intermediate and current periods. We partitioned phylogenetic beta diversity into turnover and nestedness component, and examined how introductions and extirpations led to temporal changes in alpha and beta diversity using linear regression and multiple regression models on distance matrices, respectively. Introductions and extirpations caused an increase of phylogenetic diversity (Δ+) and phylogenetic unevenness (Λ+) within the lakes, but the phylogenetic dissimilarity between lakes declined. Such trend, resulting from 60 years introductions and extirpations, was mainly due to a decline of the phylogenetic turnover, indicating that the replacement of native endemic species by widespread exotic species was the main driver of the observed phylogenetic homogenization. Temporal changes in phylogenetic and taxonomic dissimilarities were positively correlated, and taxonomic homogenization causes phylogenetic homogenization in ca. 60% of the lake pairs. Nevertheless, taxonomic homogenization turns to phylogenetic differentiation in one third of lake pairs due to the extirpation of the closely-related species and the introduction of distinct exotic species belonging to different lineages among lakes. Therefore, measuring phylogenetic diversity changes provides complementary information to taxonomy, and gives support to the Darwin’s naturalization hypothesis stipulating that species distantly related to natives easily establish in their introduction range. Our results demonstrate that half a century of anthropogenic disturbance was sufficient to blur the phylogenetic distinctiveness among lakes that resulted from the last 5 million years evolutionary history of the Yun-Gui plateau.

Fossil records of the ancient and less studied millipede order Siphonophorida are rare and only known from Oligocene-Miocene Dominican amber to date. Here, we describe a Mesozoic species of this order, Siphonophora hui sp. nov., based on two well-preserved specimens from mid-Cretaceous Burmese amber. The new species can be placed in the family Siphonophoridae by having mouthparts strongly modified into a long beak, straight antennae, the separation of tergites, pleurites and sternites, leg-like gonopods derived from 9th and 10th leg pairs, and absence of ommatidia. This discovery pushes back the fossil record of Siphonophorida by more than 60 Ma. It also demonstrates that the details of the siphonophorid body plan have remained virtually unchanged for nearly 100 million years. An enigmatic structure on the antennae of the paratype may represent either the ancestral form of the circular sensory pits, or more unlikely, the earliest occurrence of a fungus parasitic or commensal on an arthropod.

Disentangling the effects of dispersal mode on the environmental and spatial processes structuring biological assemblages is essential to understanding the mechanisms of species coexistence...

Drought is a major limiting factor of plant productivity worldwide and its incidence is predicted to increase with climate changing. Endophytes are non-pathogenic plant-associated bacteria that can play an significant role in improving plant tolerance to drought. Here, the effects of Bacillus pumilus (B. pumilus) inoculation on growth, metabolite accumulation and related protein expression, and it’s mechanism focusing on antioxidant defense of Glycyrrhiza uralensis Fisch. (G. uralensis) subjected to drought stress were investigated under controlled conditions. Drought stress induced oxidative damage and further decreased growth and secondary metabolites in G. uralensis. Exposure of inoculated plant to drought-stress led to significant increase in total biomass by 34.9%, and in oxygen species and antioxidants while decrease in lipid peroxidation level, compared to non-inoculated plants grown under similar conditions. There was a significant effect of the endophyte on plant metabolism; higher levels of total flavonoids, total polysaccharide and glycyrrhizic acid were recorded in roots of colonized plants compared to non-colonized ones. Furthermore, the expression of HMGR, SQS and β-AS, key enzymes for glycyrrhizic acid synthesis, significantly increased by B. pumilus inoculation. Taken together, our results indicated that B. pumilus improves G. uralensis growth under drought stress through the modification of antioxidants accumulation and enhances glycyrrhizic acid content by the incremental expression of key enzymes. These results will contribute to the development of a microbial agent to improve the yield and quality of medical plants exposed to environmental stresses.

The elevational alpha biodiversity gradient in mountain regions is one of the well‐known ecological patterns, but its beta diversity pattern remains poorly known. Examining the beta diversity and its components could enhance the understanding of community assembly mechanism. We studied the beta diversity pattern of the soil enchytraeids along a distinct elevational gradient (705–2,280 m) on the Changbai Mountain, the best‐preserved mountain in northeastern China. The overall abundance‐based community dissimilarity was relatively high (ca. 0.70), largely due to the balanced‐variation component (85%). The overall dissimilarity and its balanced‐variation (substitution) component were related to both local environmental heterogeneity and elevational distance, with the environmental relationships being stronger. In contrast, the abundance‐gradient (subsets) component was not related to the two gradients. The same important spatial and environmental variables were detected in structuring overall dissimilarity and substitution component, different from that in subsets component. Variation partitioning analysis showed that environmental control played a more important role than spatial (vertical and horizontal) factors in structuring the patterns of overall beta diversity and its two components. The predictive power of multivariate analysis was higher for the substitution component (nearly 50%) and overall dissimilarity (35%), but much lower for subsets components (

Background Disentangling the relative roles of environmental filtering and spatial processes in structuring ecological communities is a central topic in metacommunity ecology. Metacommunity ecology in the temperate river ecosystems has been well developed, while less attention has been paid to subtropical urban river networks. Here, we examined the ecological factors and seasonal difference in structuring macroinvertebrates metacommunity assembly in the subtropical urban river networks in Shenzhen, South China. Results Our results revealed that there was no significant distinction of macroinvertebrate community composition among seasons, with only the relative abundance of Mollusca and Odonata significantly differed in both wet and dry seasons. One possible explanation was that most macroinvertebrates are generally pollution-tolerant taxa characterized with nonseasonal life cycle. In addition, distance-based redundancy analysis and variation partitioning approach revealed that metacommunity was determined equally by the environmental and dispersal-related factors. Further, our results showed that, although a slight temporal variation of relative contribution, the identity and explanation power of ecological factors were different among seasons. Specifically, stronger environmental filtering structuring community dynamics was observed in the dry than wet seasons, which might be owing to higher environmental heterogeneity under a low water-flow condition. Moreover, we detected that the influence of spatial processes was stronger in the wet than dry seasons, indicating an obvious dispersal processes due to high connectivity among sites. Conclusion Overall, our results revealed that environmental and spatial factors equally explained variations of macroinvertebrate metacommunity, implying the necessity of considering dispersal-related processes structuring ecological communities in river bioassessment programs. Moreover, degraded habitat conditions and water quality were the predominant factors that affected macroinvertebrate communities, indicating the significance and feasibility of improving local abiotic conditions to sustain local biodiversity. Further, our findings revealed the importance of seasonal dynamics of these urban river networks in structuring macroinvertebrate metacommunity. Thereby, our study improves the understanding of ecological processes governing macroinvertebrate metacommunity and underlines the idea that community ecology studies should go beyond the single snapshot survey in river networks.

The recent delimitation of the cambalopsid genera Hypocambala and Glyphiulus is debatable. The focus of controversy is whether the presence of crests on the trunk rings is an appropriate key character dividing these two genera. To address this issue, we conducted a molecular phylogenetic analysis including species with or without crests belonging to Hypocambala and species with crests belonging to Glyphiulus. The results of the phylogenetic analysis suggest that cambalopsids with crests are monophyletic and sister to a species without crests. Hypocambala polytricha, a cambalopsid with crests that is in a clade with crested Glyphiulus species, should be transferred to Glyphiulus. Therefore, a new combination is proposed, Glyphiulus polytrichus comb. nov. In addition, a discussion on the boundary between these two genera and a description of a new species, Hypocambala zizhongi sp. nov., are provided.

Additional file 1: Supplement Table 1. Mean values ± SD of the relative abundance of macroinvertebrate groups in both wet and dry seasons, respectively. * (P < 0.05) indicate the significant difference among seasons based on Mann-Whitney U tests. Supplement Figure 1. Canonical Analysis of Principal Coordinates (CAP) ordination plots of five watershed macroinvertebrate abundance data (Bray-Curtis coefficient). Supplement Table 2. Summary of the results of Canonical Analysis of Principal Coordinates (CAP) for average differences in taxonomic composition of macroinvertebrate communities among five watersheds. Trace = sum of the canonical eigenvalues, Delta = the 1st eigenvalue. P-Values (in parentheses) were based on 999 permutations.

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.

The male of Glyphiulus formosus (Pocock, 1895) is described for the first time based on specimens collected from Shenzhen, Guangdong, China. According to the male sexual characters, this species is verified to be a member of the G. javanicus group. In addition, a DNA barcode of the partial COI gene of G. formosus is provided.

Hemienchytraeus wuhanensissp. nov. is described from hardwood forest soil in Wuhan, China. This moderately sized enchytraeid species of 6–9 mm body length is characterized by: (1) an oesophageal appendage with tertiary branches, (2) three pairs of secondary pharyngeal gland lobes in V, VI, VII, (3) five pairs preclitellar nephridia, from 5/6 to 9/10, (4) dorsal vessel originating in clitellar segments, (5) a girdle-shaped clitellum, (6) a relatively small male reproductive apparatus without seminal vesicle, and (7) spermathecae that extend to VI–VII. DNA barcodes of paratype specimens of the new species are provided. Previous species records of Hemienchytraeus from China are critically discussed.

Effects of commercial sand mining on aquatic diversity are of increasing global concern, especially in parts of some developing countries. However, understanding of this activity on the diversity of macroinvertebrates remains focused on the α component of species diversity, rather than community functioning. Thus, there remains much uncertainty regarding how each component of taxonomic (TD) and functional (FD) diversity respond to the activity both in freshwater and marine environments. Here, we assessed the effect of sand dredging on α, β and γ components of TD and FD during different dredging periods based on the response of macroinvertebrate communities over 4 years in the second largest freshwater lake in China. After three years of active dredging, substantial reductions in each component (α, β and γ) of TD and FD were observed within the dredged area. Moreover, after one year of natural recovery, a distinct restoration was observed with an obvious return in multiple facets of TD and FD indices. No such changes were observed within the adjacent and reference areas. Decreases in the multiple components of TD and FD within the dredged area were most likely associated with the direct extraction of substrate and associated benthic fauna and indirect variations of the water and sediment environment (e.g., increases in water depth and decreases in %Clay). Furthermore, dispersal processes and mass effects mainly contributed to the maintenance of TD and FD during the dredged and recovery stages. In addition, the fast recovery of TD and FD was also related to the simple taxonomic structure and highly connected nature of the study area. Our results suggest that a more precise experimental design (BACI) should be pursued to avoid potentially confounding effects (e.g., natural disturbance) because the sensitivity of diversity indices depends upon different experimental designs. Moreover, measurement of the impacts of sand dredging on macroinvertebrate diversity can be undertaken within a rigorous framework for better understanding the patterns and processes of each component of TD and FD under the sand dredging disturbance.

It has been reported that drought stress adversely affects the growth and yield of Glycyrrhiza uralensis, Chinese liquorice, in agricultural production. Bacillus pumilus, an important plant growth-promoting bacterium, play a significant role in improving plant tolerance to abiotic stress. However, the role of Bacillus pumilus G5 in resisting drought stress is largely unknown. In the present study, we found that drought stress significantly inhibited the growth and reduced the biomass of G. uralensis seedlings by restraining C- and N-metabolism, while this could be effectively reversed by B. pumilus G5 inoculation. Specifically, B. pumilus G5 significantly increased the content of primary metabolites such as soluble sugar, soluble protein, and free amino acids by regulating the C and N metabolic processes in G. uralensis seedlings. Moreover, B. pumilus G5 increased the content of glycyrrhizic acid, one of the important secondary metabolites, likely mediated through the increased content of primary metabolites and by recovering the expression of three key enzymes, HMGR, SQS, and β-AS, in the biosynthesis of glycyrrhizic acid. Interestingly, the regulating effect of B. pumilus G5 inoculation on promoting the accumulation of glycyrrhizic acid and increasing the expression of synthesis-related genes is spatially selective. In summary, our findings suggest that B. pumilus G5 could alleviate adverse effects induced by drought stress on the growth of G. uralensis seedlings by regulating C- and N-metabolisms that further triggered the accumulation of secondary metabolites, and this finally improved the drought tolerance of cultivated G. uralensis seedlings.

In parts of developing countries, the over-exploitation of sands from inland waters has led to serious environmental concerns. However, understanding of the impacts of commercial sand dredging on inland water ecosystem functions remains limited. Herein, we assess the effects of this activity on the functional structure of the macroinvertebrate community and its recovery processes based on a 4-year survey, in the South Dongting Lake in China. Our result showed a simplified macroinvertebrate functional structures within the dredged area, as evidenced by a loss of certain trait categories (e.g., oval and conical body form) and a significant reduction in trait values due to the direct removal of macroinvertebrates and indirect alternations to physical environmental conditions (e.g., water depth and %Medium sand). Moreover, clear increases were observed in certain trait categories (e.g., small body size and swimmer) resulting from the dredging-related disturbance (e.g., increased turbidity) within the adjacent area. Furthermore, one year after the cessation of dredging, a marked recovery in the taxonomic and functional structure of macroinvertebrate assemblages was observed with most lost trait categories returning and an increase in the trait values of eight categories (e.g., body size 1.00–3.00 cm and oval body form) within the dredged and adjacent area. In addition, dispersal processes and sediment composition were the main driver for the structuring of the macroinvertebrate taxonomic and functional assemblages during the dredging stages, whilst water environmental conditions dominated the taxonomic structure and dispersal processes determined the functional structure during the recovery stage. Implications of our results for monitoring and management of this activity in inland waters are discussed.

Hitherto, 24 species of the Glyphiulus javanicus group have been recorded, all endemic to Southeast Asia, including 14 in China. Nevertheless, this species group needs further exploration. In this context, four new species of this group are described, all collected from limestone caves in Southern China: G. calceus sp. n., G. foetidus sp. n., G. guangnanensis sp. n., and G. impletus sp. n. They can be separated easily from each other and other congeners by their carinotaxic formulae, the structures of male legs I, and the gonopods. Due to the absence of any troglomorphic traits in our specimens, they may be troglophilic only.

The experiment was carried out with plants grown in pots with soil to determine the effects of different levels of water stress on roots biomass, secondary metabolites in roots and endogenous hormones (IAA, GA3 and ABA), relative water content (RWC), tissue density (TD) in leaves of Stellaria dichotoma L.var. lanceolata Bge. The results showed that roots biomass, total saponins content firstly increased and then decreased with increasing water stress levels. RWC significantly decreased with increasing water stress levels while the change of TD was inverse. The concentration of IAA and GA3 firstly increased and then decreased with increasing water stress levels and reached maximum value under 60–70% of field capacity (FC). However, ABA concentration sharply increased under ≤40–50% FC. With correlation analysis and principal component analysis (PCA), total flavonoids content had significant positive with ABA and TD, but had a negative correlation with RWC. Roots biomass had a significant negative correlation with ABA, while ABA had a very significant negative correlation with RWC and a significant positive correlation with TD. The PCA partitioned the total variance into 2 PCs contributing maximum (90.793%) to the total diversity among the water stress due to the study of various traits. The higher eigenvector of PC I is RWC and ABA, whereas the higher and positive eigenvector of PC II is GA3, total saponins content and IAA. Our study indicated that roots biomass and secondary metabolites of S. dichotoma were first increases and then decreases with increasing water stress levels. Thus, moderate water stress (60–70% or 80–90% FC) was suitable for roots biomass formation and active ingredient accumulation, which was affected by endogenous hormones and water status.

Soil salinity, drought, metal toxicity, and ultraviolet-B radiation were major abiotic stresses that limit plant growth and productivity by disrupting the plants' cellular ionic and osmotic balance; legumes, a diverse plant family, suffered from these abiotic stresses. Although silicon (Si) is generally considered non-essential for plant growth and development, Si uptake by plants could facilitate plant growth by reducing biotic and abiotic stresses. There is however, a lack of systematic study on Si uptake benefits and mechanism on legumes because legumes reject Si uptake. Here, we reviewed the beneficial role of Si in enhancing abiotic stress tolerance in legumes and highlighted the mechanisms through which Si could improve abiotic stress tolerance in legumes. Future research needs for Si mediated alleviation of abiotic stresses in legumes are also discussed.

Understanding how environmental changes affect life-history traits is important for predicting population dynamics of a species. As one of the most pervasive forms of environmental changes in freshwater systems, eutrophication can change life-history traits of freshwater animals through density-dependent/independent processes. However, empirical evidence remains scarce regarding the mechanisms by which eutrophication influences life-history traits. We conducted a field study linking eutrophication, life-history traits and population density in a population of Margarya melanioides in Lake Dianchi, the largest lake of the Yun-Gui plateau in China and the most eutrophicated by humans, over 14 months in 2009-2010. We estimated key life-history traits (growth and reproduction) of M. melanioides in 2009-2010. Then, by comparing some life-history traits with those recorded in 1931-1933 (when the extent of eutrophication was comparatively low), we found that this snail had increased its fecundity (from 1.07 to 4.24 offspring/brood-bearing female) and the proportion of females with broods (23.6 to 77.4%), decreased its body size (54.2 to 47.6 mm) and the threshold size for reproduction (46 to 35 mm), and distorted its female/male sex ratio (1.6:1 to 0.97:1). These findings suggest that M. melanioides has adapted some life-history traits in response to intensified eutrophication. A structural equation model indicated that eutrophication influenced the reproduction of this snail through two related but opposing pathways: primarily by decreasing its population size to reduce its reproduction and secondarily by directly promoting its reproduction. Our results not only support the significance of eutrophication in determination of life-history traits of freshwater animals, but also suggest that density-dependent effects on reproduction may be stronger than direct environmental influences when population size is small.

Identifying naturally-regulated spatial and temporal variations of benthic macroinvertebrates is critical to effective assessment and conservation of aquatic ecosystems, but little is known about these variations in large rivers in East Asian monsoon region. Here, we address this issue by measuring within-one-year longitudinal and seasonal variability in macroinvertebrate assemblages in such a broadly natural river across its whole watershed. Along longitudinal gradients, taxon richness, Shannon–Wiener diversity and mayflies and caddisflies significantly decreased downstream but chironomids and oligochaeta increased. Taxon richness, diversity indices, and abundance of most taxa all had lowest value in summer. Assemblage structure showed both significant but larger longitudinal than seasonal variations, with a clear separation of upstream and most midstream sites from downstream ones in ordination plot. Different environmental and spatial variables were significant for distinguishing macroinvertebrate assemblages among four seasons, although substrate and PCNM1 emerged as important in all seasons. Variance partitioning analyses indicated stronger environmental control than spatial structuring of community composition in all seasons, with pure environmental factors explaining most community variation. These observed patterns contribute to understanding of sources of uncertainty in bioassessment and thus have implications for ecological monitoring and assessment using macroinvertebrates in rivers in monsoon regions.

Due to the difficulty of identifying many taxa of freshwater invertebrates to species, many researchers have assessed the utility of surrogates for species-level identifications (e.g. higher taxa) in bioassessment programs. Here, we examined the efficiency of two different approaches to species surrogacy, one using coarser taxonomic resolution and a second approach based on random aggregation (“Best practicable aggregation of species”, BestAgg), in portraying patterns of stream macroinvertebrates in Central China. The main objectives were: (1) to compare the discriminatory power of biodiversity indices and assemblage structure for different levels of human disturbances based on different taxonomic resolution and on BestAgg; (2) to identify the congruence of assemblage-environment and biodiversity-indices-environment relationships for datasets at the species level versus those at surrogate levels. We found that genus-level and BestAgg datasets accurately reproduced the pattern of species-level communities, whereas family- and order-level datasets did not. Specifically, both genus-level and BestAgg approaches performed almost as well as species-level data in distinguishing sites subjected to different disturbance levels. Most of the environmental variables that were important for species-level assemblages, also emerged as significant when analyzing genera and BestAgg surrogates, as shown by both analyses of indices and assemblage composition according to distance-based ordination models. Our results suggest that genus-level taxonomy, which resulted in the least loss of ecological information relative to species-level identification, is sufficient in studies of community ecology and bioassessment of stream macroinvertebrates in Central China. In addition, the BestAgg approach, which required identification of fewer taxa than genus-level analysis, has a similar ability to depict multivariate patterns of macroinvertebrate assemblages and differentiate different disturbance levels. Applying our results could enhance speed and cost-effectiveness of freshwater biomonitoring and bioassessment programs; however, independent determination of best taxonomic level and BestAgg will be required whenever a new geographic area or habitat type is assessed.

Aim Introductions of exotic species have globally modified the structure and function of native assemblages and are recognized as one of the major threats to biodiversity. The current patterns, processes and consequences of invasion have been intensively studied globally, but studies reporting the long-term dynamics of invasions over large areas are rare. Here, we measured how the temporal changes in fish assemblage composition in a Chinese highland isolated-lake landscape drive taxonomic dissimilarity and its turnover component over three successive time periods spanning the last 75 years. Location Yun–Gui Plateau, 15 isolated lakes. Methods The Sorensen and Simpson indices were used to quantify changes in taxonomic dissimilarity and its turnover component over 1940–2015. Results We report a decline of taxonomic dissimilarity between lakes through time, mainly due to a decrease in species turnover. Such a homogenization process was due to the combined effects of the invasion of the same non-native species in most lakes and of extirpation of narrow endemic species. The strong decline in species dissimilarity and turnover was triggered by a high historical level of dissimilarity among assemblages. At a regional scale, the combined effect of introductions and extirpations modified the distance decay of taxonomic similarity between lakes. Surprisingly, this beta-diversity gradient is currently no longer supported by biogeographic and evolutionary processes, but by the human-mediated introduction of distinct exotic species in some lakes. Moreover, an extinction debt process was evident as extirpations sometimes occurred many years after the introduction of non-native species. Main conclusions Our study highlights that high historical differentiation of fishes in isolated lakes has turned to homogenization with dramatic loss of endemic species due to intensive introductions. This provides a striking example of human domination over an extended lake landscape and its associated irreparable biodiversity damages on isolated systems historically dominated by narrow endemic species.