Abundance Of Dominant Species Research Articles

Obtaining accurate population estimates with reduced workload and lower fish mortality in multi-mesh gillnet sampling of a large pre-alpine lake.

The EU Water Framework Directive requires monitoring of the ecological status of lakes, with fish as a relevant class of biotic quality indicator, but monitoring fish populations in large lakes is demanding. This study evaluated use in Lake Constance of a novel multi-mesh gillnet modified to reduce catch numbers. In direct comparison with conventional European Committee for Standardization (CEN) nets we achieved 48% reduction in fish mortality with 38% less labour for tasks directly influenced by fish catch numbers, while maintaining comparable species composition and catch per unit effort. Comparison of mesh sizes indicated no significant reduction in species detection in area-reduced panels of the small mesh sizes, while total observed species richness was greater when using the modified nets. Differences in benthic species communities among depth strata were common, while those of pelagic zones were more homogeneous and did not differ significantly with depth. Catches of different net types from the same depth stratum did not exhibit significant differences. The dominance structure of the most common species, relevant to lake assessment, was similar in catches of both net types, suggesting overall superiority of the modified nets in Lake Constance. Sampling conducted according to standard European CEN protocol, while deploying 60% fewer nets, yielded sufficiently precise abundance estimates for monitoring shallow areas of the benthic zone. A 50% difference in the abundance of dominant species was detected among sampling events with a certainty of 95%. The sample did not provide comparable accuracy in deep benthic strata or the pelagic zone, but was adequate to record complete inventories of species present. Based on this trial data, a new stratified sampling design is proposed for monitoring large lake fish communities for ecological assessment. Depth-dependent fish communities were used to calculate the required number of nets, which resulted in a 69% reduction for the entire lake compared to the CEN calculation method. Using the modified nets increases the feasibility of performing WFD surveys, by reducing effort and cost, while the simultaneous halving of fish mortality minimises the negative impact of fish surveys.

Uncovering the mechanisms of how corn steep liquor and microbial communities minimize cadmium translocation in Chinese cabbage.

Corn steep liquor-assisted microbial remediation has been proposed as a promising strategy to remediate cadmium (Cd)-contaminated soil. In this study, we determined Bacillus subtilis (K2) with a high cadmium (Cd) accumulation ability and Cd resistance. However, studies on this strategy used in the Cd uptake of Chinese cabbage are lacking, and the effect of the combined incorporation of corn steep liquor and K2 on the functions and microbial interactions of soil microbiomes is unclear. Here, we study the Cd uptake and transportation in Chinese cabbage by the combination of K2 and corn steep liquor (K2 + C7) in a Cd-contaminated soil and corresponding microbial regulation mechanisms. Results showed that compared to inoculant K2 treatment alone, a reduction of Cd concentration in the shoots by 14.4% and the dry weight biomass of the shoots and the roots in Chinese cabbage increased by 21.6% and 30.8%, respectively, under K2 + C7 treatment. Meanwhile, hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels were decreased by enhancing POD and SOD activity, thereby reversing Cd-induced oxidative damage. Importantly, inoculation of K2 would decrease the diversity of the microbial community while enhancing the abundance of dominant species. These findings provide a promising strategy for reducing the Cd accumulation in Chinese cabbage and recovering soil ecological functions.

A test of the loose-equilibrium concept with long-lived organisms: Evaluating temporal change in freshwater mussel assemblages.

The loose-equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change. Long-lived, slow-growing animals typically respond slowly to environmental change, and their assemblage dynamics may respond over decades, which transcends most ecological studies. Unionid mussels are valuable for studying dynamics of long-lived animals because they can live >50 years and occur in dense, species-rich assemblages (mussel beds). Mussel beds can persist for decades, but disturbance can affect species differently, resulting in variable trajectories according to differences in species composition within and among rivers. We used long-term data sets (10-40 years) from seven rivers in the eastern United States to evaluate the magnitude, pace and directionality of mussel assemblage change within the context of the LEC. Site trajectories varied within and among streams and showed patterns consistent with either the LEC or directional change. In streams that conformed to the LEC, rank abundance of dominant species remained stable over time, but directional change in other streams was driven by changes in the rank abundance and composition of dominant species. Characteristics of mussel assemblage change varied widely, ranging from those conforming to the LEC to those showing strong directional change. Conservation approaches that attempt to maintain or create a desired assemblage condition should acknowledge this wide range of possible assemblage trajectories and that the environmental factors that influence those changes remain poorly understood.

The influence of dietary patterns on skin bacterial diversity, composition, and co-occurrence relationships at forearm and neck sites of healthy Korean adults.

Diet and nutrition are important aspects of skin physiology and health. However, the influence of diet on the bacterial flora of different skin sites is not well understood. Therefore, we investigated the relationship between dietary patterns (DPs) and skin bacterial flora on the forearm (a dry site) and the neck (a sebaceous site) of healthy Korean adults. In metagenomics analysis, Shannon and Simpson Indices were higher on the forearm than on the neck and were negatively correlated with the two dominant species, Cutibacterium acnes and Staphylococcus epidermidis on two skin sites. In addition, the Simpson index of the forearm was positively associated with DP1 (characterized by a high intake of vegetables, mushrooms, meat, fish and shellfish, seaweed, and fat and oil), while that on the neck was negatively associated with DP2 (characterized by a high intake of fast food). A high intake of DP1 was associated with a lower abundance of dominant species including C. acnes and higher degrees of the co-occurrence network, whereas a high intake of DP2 was associated with the opposite pattern. Specific diets may impact both skin bacterial diversity and composition, as well as the co-occurrence of bacteria, which may vary across different skin sites.

Amazon River plume habitats shape planktonic cnidarian assemblages in the Western Atlantic.

The impact of the Amazon River freshwater plume on planktonic cnidarians over neritic and oceanic provinces is unknown. To provide further knowledge we took advantage of an oceanographic cruise performed in October 2012 in the Western Atlantic off the North Brazilian coast (8°N, 51°W-3.5°S, 37°W). A complex and dynamic system was observed, with strong currents and eddies dispersing the plume over a large area. Our results show that the Amazon River shapes marine habitats with a thin highly productive surface layer compressed by a deeper oxygen minimum zone both over the shelf and in the open ocean. We hypothesized that such habitat structure is particularly advantageous to planktonic cnidarians, which have low metabolic rates, being able to survive in hypoxic zones, resulting in high species richness and abundance. Over the shelf, distinctions were sharp and the area under the influence of the plume presented a diverse assemblage occurring in large abundance, while outside the plume, the hydromedusa Liriope tetraphylla was dominant and occurred almost alone. Divergences in the oceanic province were less pronounced, but still expressive being mostly related to the abundance of dominant species. We concluded that Amazon River plume is a paramount physical feature that profoundly affects the dynamics of the mesoscale habitat structure in the Western Equatorial Atlantic Ocean and that such habitat structure is responsible for shaping planktonic cnidarian assemblages both in neritic and oceanic provinces.

Varied plant species' responses to climate and environmental change on Mount Kenya after 40 years

AbstractTropical alpine areas are some of the most vulnerable areas in the world to climate change. Their plant communities have narrow thermal niches and have limited geographic areas to expand. Here we examine changes in plant species' abundance and distribution in the Teleki Valley (3900–4500 m asl) of Mount Kenya using a spatially explicit vegetation survey from 1980. Vascular plant species were re‐sampled in 35 plots across the valley, and additional size and density data were collected for the two Dendrosenecio species. Overall species richness and diversity were lower in 2021 than in 1980, and the abundance of dominant species had declined. Changes in elevation suggested both upward and downward shifts had occurred. Dendrosenecio keniodendron exhibited a shift towards the valley bottom as well as a change in population structure towards younger individuals. The dominant environmental factors affecting plant composition were similar in both 1980 and 2021, namely elevation, vegetation cover and the presence of D. keniodendron. This keystone species plays a significant role in shaping communities but is undergoing rapid demographic changes, which may have cascading implications on the ecology of the system.

Adaptability of agricultural soil microbial nutrient utilization regulates community assembly under mulching measures on the Loess Plateau

Soil microbial nutrients and resource availability improve with mulching in agroecosystems, resulting in changes of soil microbial nutrient utilization strategies. However, the responses of soil microorganisms to nutrient utilization processes to regulate community assembly and thus maintain resource availability have not been clarified. Here, we performed a long-term field experiment with mulching measures, including no-mulching (NM), straw mulching (SM), plastic mulching (PM), and ridge mulching (RM), conducted on the Loess Plateau of China, to explore the community assembly process in response to microbial nutrient utilization. Microbial nutrient utilization strategies were analysed by measuring soil nutrients, microbial biomass, and extracellular enzyme activities. The results showed that PM and RM acquired C and N nutrients by secreting C- and N-extracellular enzymes in response to C:N- and C:P imbalances in soil chemistry, thereby reducing the nutrient limitation on microbial metabolism and improving microbial C utilization efficiency (CUE). Soil extracellular enzymatic stoichiometry increased and N utilization efficiency (NUE) decreased under mulching and drove an increase in beta-diversity and dominant species abundance in fungal communities. Mulching measures promoted the modular distribution of sensitive microorganisms and aggregation of fungal networks under PM and RM by reducing the stoichiometric imbalance and extracellular enzymatic N:P. At the same time, the microbial community assembly gradually changed from a stochastic to a deterministic process in response to the alleviation of soil C:P imbalance and changes in microbial nutrient utilization, in which the fungal community was dominant. In conclusion, soil microorganisms adaptively responded to changes in soil microbial nutrient utilization through the enhancement of aggregation of fungal co-occurrence networks and deterministic assembly processes. This study provides a better understanding of the impact of mulching on microbial nutrient utilization strategies from a community assembly perspective.

Regulatory Effects Mediated by Enteromorpha prolifera Polysaccharide and Its Zn(II) Complex on Hypoglycemic Activity in High-Sugar High-Fat Diet-Fed Mice.

In order to investigate and develop functional foods of marine origin with hypoglycemic activity, Enteromorpha prolifera polysaccharide-Zn(II) (EZ) complex was first prepared by marine resourced E. prolifera polysaccharide (EP) and ZnSO4 and their anti-diabetes activities against high-sugar and high-fat-induced diabetic mice were evaluated. The detailed structural characterization of EZ was elucidated by UV-Vis spectroscopy, infrared spectroscopy, and monosaccharide composition determination. The pharmacological research suggests that EZ has a potent hypoglycemic effect on high-sugar and high-fat-induced diabetic mice by inhibiting insulin resistance, improving dyslipidemia, decreasing inflammatory status, repairing pancreas damage, as well as activating the IRS/PI3K/AKT signaling pathway and regulating GLUT2 gene expression. At the same time, microbiota analysis indicates that a high dose of EZ could enhance the abundance of dominant species, such as Staphylococcaceae, Planococcaceae, Muribaculaceae, Aerococcaceae, and Lacrobacillaceae, in intestinal microbiota distribution. Thus, EZ could be considered as a potential candidate for developing an ingredient of functional foods for Zn(II) supplements with hypoglycemic activity.

Response of Water Stress and Bacterial Fertilizer Addition to the Structure of Microbial Flora in the Rhizosphere Soil of Grapes Under Delayed Cultivation

ABSTRACT The objectives of this study were to reveal the soil microbial structures in the rhizosphere soil of the delayed cultivation and to evaluate the effects of water stress and bacterial fertilizer on major bacteria. The experiment was conducted in 2019 in Yongdeng County, Gansu Province. Three treatments of water regulation were set, including the moderate water stress, mild water stress and adequate water supply treatment with the bacterial fertilizer added at the levels of no addition (0 g), small addition (75 g) and large addition (150 g), respectively. The results showed that the relative abundance of dominant species of soil microorganisms was significantly higher under sufficient water supply and mild water stress treatment than under moderate water stress treament. Under the mild water stress condition, the relative abundance of the most dominant species in each classification level sequentially decreased with the bacterial fertilizer added increasingly. Adding a small amount of bacterial treatment fertilizer to moderate water stress can improve the overall abundance of soil microbial communities during the growth period of new shoots. It was found that Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria, Firmicutes, Acidobacteria, Chloroflexi, Planctomycetes, Thaumarchaeota, Verrucomicrobia, and the other bacteria were the major bacterial phyla in the rhizosphere soil of delayed cultivation grapes, among, which Proteobacteria were the most dominant group. Therefore, adding a small amount of bacterial fertilizer under the mild water stress treatment can not only improve the diversity and richness of soil microorganisms during the fruit expansion period, but also significantly save water resources compared with the traditional irrigation regimes.

Dominant species determine grazing effects on the stability of herbaceous community production at multiple scales in drylands

Abstract Sustainable provision of critical ecosystem services in drylands is reliant on their stability under anthropogenic disturbances. Livestock grazing and shrub encroachment are the primary drivers of disturbance that impact their biodiversity and production dynamics. However, the effects of grazing on the stability at multiple scales, particularly following the transition from grass‐dominated to shrub‐encroached drylands, is still largely unexplored. Here, we conducted comparable sheep‐grazing experiments in two types of drylands (grass‐dominated vs. shrub‐encroached grasslands) on the Mongolia Plateau to explore the effects of grazing and shrub encroachment on biodiversity and stability at multiple scales. We examined how grazing affected the temporal stability of aboveground biomass in herbaceous communities in both grass‐dominated and shrub‐encroached grasslands, through two potential mechanisms: insurance effects and changes in the population‐level stability of individual species. We found that an increase in sheep grazing intensity had significant and negative effects on insurance effects by decreasing both species asynchrony and spatial asynchrony but it had no effects on population stability, consequently leading to reductions in herbaceous community stability of the grasslands. However, grazing‐increased insurance effects cancelled out grazing‐decreased population stability, contributing to no changes in the community stability of shrub‐encroached grasslands. Likely, because grazing‐induced reductions in the relative abundance of the dominant species were more noticeable in shrub‐encroached grasslands than that of in grasslands. Moreover, the grazing‐decreased abundance of dominant species was directly correlated to increases in insurance effects in shrub‐encroached grasslands but not in grasslands, despite the positive relationships between population stability and the relative abundance of the dominant species in both grass‐dominated and shrub‐encroached drylands. Synthesis and applications. Our results indicate that grazing can decrease the stability of herbaceous production in drylands but this negative effect is attenuated with the transition from grasslands to shrub‐encroached grasslands, suggesting that grazing effects on herbaceous community stability can be altered by shrub encroachment in drylands. Furthermore, the stability of dominant grasses plays a crucial role in stabilizing herbaceous communities and should be considered in promoting sustainable ecosystem functioning and services in drylands.

Enhanced ethanol-driven carboxylate chain elongation by Pt@C in simulated sequencing batch reactors: Process and mechanism

Carboxylate chain elongation can create value-added bioproducts from the organic waste. The effects of Pt@C on chain elongation and associated mechanisms were investigated in simulated sequencing batch reactors. 5.0 g/L of Pt@C greatly increased the synthesis of caproate, with an average yield of 21.5 g COD/L, which was 207.4% higher than the trial without Pt@C. Integrated metagenomic and metaproteomic analyses were used to reveal the mechanism of Pt@C-enhanced chain elongation. Pt@C enriched chain elongators by increasing the relative abundance of dominant species by 115.5%. The expression of functional genes related to chain elongation was promoted in the Pt@C trial. This study also demonstrates that Pt@C may promote overall chain elongation metabolism by enhancing CO2 uptake of Clostridium kluyveri. The study provides insights into the fundamental mechanisms of how chain elongation can perform CO2 metabolism and how it can be enhanced by Pt@C to upgrade bioproducts from organic waste streams.

Rainfall Influences the Patterns of Diversity and Species Distribution in Sandy Beaches of the Amazon Coast

The Amazon region is one of the Earth’s hotspots of biodiversity and has a pivotal role in climate regulation. Yet, little is known about its coastal biodiversity. Here, we performed the first assessment of macrobenthic diversity and ecological patterns of sandy beaches north of the Amazon River delta, the world’s largest freshwater input into the oceans. By assessing spatial and temporal changes in the soft-bottom biodiversity and environmental variables of three beaches (Goiabal, Nazaré, and Sumaúma) in the northernmost stretch of the Brazilian coast, we found low richness (14 taxa, overall; Goiabal: 3.27 ± 1.78; Nazaré: 2.34 ± 1.29; Sumaúma: 2 ± 0.67) and diversity (Goiabal: 0.72 ± 0.52; Nazaré: 0.62 ± 0.46; Sumaúma: 0.55 ± 0.39) across 2949 individuals with great dominance of estuarine species (notably Nephthys fluviatis and Sphaeromopsis mourei). Abundance was higher during rainy periods, and the same pattern was observed for richness and diversity in comparison to transitional periods, at least on Nazaré Beach. Environmental heterogeneity was reduced during rainy periods, resulting in a higher abundance of dominant species and lower beta diversity. Most species presented aggregated distribution at the upper intertidal zone, and changes in macrobenthic assemblages were linked to variations in rainfall and organic matter content in the sediment. Given the ecological uniqueness and the severe erosional process affecting the northern coast of the Amazon region, our results provide essential baseline knowledge to better understand the patterns and processes influencing its understudied biodiversity. We advocate that further studies expand our findings to support the conservation of this region.

Diminishing influence of negative relationship between species richness and evenness on the modeling of grassland α-diversity metrics

Species richness and evenness have been widely used to investigate the spatiotemporal variation of α-diversity. However, some studies have indicated that a negative relationship exists between species richness and evenness. The question is how the differing sensitivity of α-diversity metrics and interactive behavior between richness and evenness affect the modeling of α-diversity variation. Here, we explored the response of species diversity, represented by three Hill numbers (i.e., species richness, exponential of Shannon index – expShannon, and inverse of Simpson index – invSimpson) focusing on the abundance of rare and common species, and Pielou index underlining the evenness of a community, to α-diversity variation through structural equation modeling (SEM). The model scheme integrated three categories of variables, spectral variation hypothesis (SVH), community pattern, and vertical structure, along the precipitation gradient spanning three steppes, including meadow steppe, typical steppe, and desert steppe. Our results showed that there were large differences in species richness across the three steppes, with v-shaped patterns emerging along the gradient (low-point in the typical steppe). Differences between steppes were diminished in the expShannon or invSimpson indices, though the v-shaped patterns persisted. The Pielou index showed the opposite pattern, with the peak in the typical steppe. Accordingly, a negative relationship between species richness and Pielou index was found across the three steppes. The concurrent increases in annual species number and dominant species abundance in response to precipitation variations led to the negative relationship. As a result, the SEM fitness on expShannon and invSimpson indices over the region was substantially diminished by the negative relationship. Overall, community pattern better explained the variation in species richness, invSimpson and Pielou indices. The performance of SVH differed among α-diversity metrics due to the collinearity with the variables of community pattern and vertical structure. This study emphasizes the variability of α-diversity metrics in response to environmental change. Particularly, distinguishing the asynchronous behaviors between species richness and evenness is paramount to account for α-diversity variation over heterogeneous ecosystems.

Floristic diversity, composition and dominance across Amazonian forest types respond differently to latitude

AbstractAimThe latitudinal biodiversity gradient is considered a first‐order biogeographical pattern for most taxonomic groups. Latitudinal variation in plant diversity is not always consistent, and this could be related to the particular characteristics of different forest types. In this study, we compare latitudinal changes in floristic diversity (alpha diversity), composition (beta diversity) and dominance across different tropical forest types: floodplain, terra firme and submontane forests.LocationWestern Amazonia (Ecuador, Peru and Bolivia).TaxonWoody plants.MethodsWe inventoried 1978 species and 31,203 individuals of vascular plants with a diameter at breast height ≥ 2.5 cm in 118 0.1‐ha plots over an 1800 km latitudinal gradient in three different forest types. The relationships between alpha diversity, latitude and forest type were analysed using generalised linear mixed models. Semi‐parametric permutational multivariate analysis of variance was used to investigate the effects of latitude and forest type on beta diversity. Dominant species abundances were correlated with non‐metric multidimensional scaling ordination axes to reflect their contributions in shaping changes in beta diversity.ResultsAlpha diversity increased towards equatorial latitudes in terra firme and submontane forests but remained relatively constant in floodplains. Beta diversity of all forest types changed with latitude, although less clearly in floodplains. Also, in floodplain forests, there were fewer dominant species contributing to beta diversity and more species homogeneous along the gradient.Main ConclusionsLatitudinal diversity patterns are manifested in alpha and beta diversity since latitude summarizes climatic and edaphic changes. However, we found different responses of each forest type. In floodplain forests, inundation regime is a stronger predictor than latitude, limiting floristic diversity and composition. Changes in dominant species abundance over gradients explained species composition, but floodplain forests harboured more homogeneous dominant species than well drained forests. It is key to study environmental trends and habitat characteristics of each forest type to understand their species diversity and dominance patterns.

Intestinal microbiota perturbations in the gastropod Trochus niloticus concurrently exposed to ocean acidification and environmentally relevant concentrations of sulfamethoxazole

Ocean acidification (OA) and antibiotic pollution pose severe threats to the fitness of keystone species in marine ecosystems. However, the combined effects of OA and antibiotic pollution on the intestinal microbiota of marine organisms are still not well known. In this study, we exposed the herbivorous gastropod Trochus niloticus, a keystone species to maintains the stability of coral reef ecosystems, to acidic seawater (pH 7.6) and/or sulfamethoxazole (SMX, 100 ng/L, 1000 ng/L) for 28 days and determined their impacts on (1) the accumulation of SMX in the intestine of T. niloticus; (2) the characteristics of the intestinal microbiota in T. niloticus; (3) the relative abundances of sulfonamide resistance genes (i.e., sul1 and sul2) and intI1 in the intestinal microbiota of T. niloticus. Our results show that OA exposure leads to dramatic microbiota dysbiosis in the intestine of T. niloticus, including changes in bacterial community diversity and structure, decreased abundances of dominant species, existences of characteristic taxa, and altered functional predictions. In addition, SMX exposure at environmentally relevant concentrations had little effect on the intestinal microbiota of T. niloticus, whether in isolation or in combination with OA. However, after exposure to the higher SMX concentration (1000 ng/L), the accumulation of SMX in the intestine of T. niloticus could induce an increase in the copies of sul2 in the intestinal microbiota. These results suggest that the intestinal health of T. niloticus might be affected by OA and SMX, which might lead to fitness loss of the keystone species in coral reef ecosystems.

Drought has inconsistent effects on seed trait composition despite their strong association with ecosystem drought sensitivity

Abstract Seeds provide the basis of genetic diversity in perennial grassland communities and their traits may influence ecosystem resistance to extreme drought. However, we know little about how drought effects the community functional composition of seed traits and the corresponding implications for ecosystem resistance to drought. We experimentally removed 66% of growing season precipitation for 4 years across five arid and semi‐arid grasslands in northern China and assessed how this multi‐year drought impacted community‐weighted means (CWMs) of seed traits, seed trait functional diversity and above‐ground net primary productivity (ANPP). Experimental drought had limited effects on CWM traits and the few effects that did occur varied by site and year. For three separate sites, and in different years, drought reduced seed length and phosphorus content but increased both seed and seed‐coat thickness. Additionally, drought led to increased seed functional evenness, divergence, dispersion and richness, but only in some sites, and mostly in later years following cumulative effects of water limitation. However, we observed a strong negative relationship between drought‐induced reductions in ANPP and CWMs of seed‐coat thickness, indicating that a high abundance of dominant species with thick seeds may increase ecosystem resistance to drought. Seed trait functional diversity was not significantly predictive of ANPP, providing little evidence for a diversity effect. Our results suggest that monitoring community composition with a focus on seed traits may provide a valuable indicator of ecosystem resistance to future droughts despite inconsistent responses of seed trait composition overall. This highlights the importance of developing a comprehensive seed and reproductive traits database for arid and semi‐arid grassland biomes. Read the free Plain Language Summary for this article on the Journal blog.

EDNA assessment of pelagic fish diversity, distribution, and abundance in the central Pacific Ocean

In open ocean environment with rich biodiversity, the assessment of fish resources is critical to the development of marine ecosystems and the sustainable use of resources. Environmental DNA (eDNA) metabarcoding is a new, constantly evolving tool and has recently been used to examine deep-sea eukaryotic diversity and communities. Here, eDNA metabarcoding was used to monitor fish populations in the central Pacific Ocean to understand the distribution of marine biodiversity in the region and investigate the abundance of dominant species. Water samples in present study were collected from three habitats, a total of 73 fish species from 41 families were detected, of which, 15 fish species from 10 families were found to be dominant species. What is more, the dominant species: Elagatis bipinnulata, Encrasicholina punctifer, Euthynnus affinis, lisha elongata, Nomeus gronovii, Reinhardtius hippoglossoides, Vinciguerria nimbaria had significant differences between habitats (p<0.05 or p<0.01). Alpha diversity indicated that the fish community composition in the three habitats was generally high, which was the highest at the Equator habitat. Beta diversity based on Bray–Curtis and Jaccard indices indicated that the fish composition of the three habitats overlapped in part, but there were not significantly different (p >0.05). Regression analyses indicated that there was an overall correlation in the biomass and reads richness (p <0.05) of Thunnus obesus and Katsuwonus pelami This study not only verities the validity and accuracy of eDNA technology applied to pelagic fish biodiversity assessment but also provides systematic cases for fish resource surveys in other sea areas and lays the foundation for oceanic fish resource monitoring.

Long-term changes in zooplankton in the Changjiang estuary from the 1960s to 2020

The Changjiang estuary (CJE) is a large estuary that is affected by multiple anthropogenic stressors and climate change. The long-term trend of zooplankton in the CJE is an important indicator of the ecological response to stressors. We applied the Mann–Kendall trend analysis and Pettitt test to detect the trend and breakpoints of the biomass of the large mesozooplankton (LMZ; 505–20 000 μm) in four seasons, abundance of main LMZ taxa in summer from the 1960s to 2020, and abundance of dominant species in summer from 2000 to 2020 in the CJE. Results showed that LMZ biomass increased significantly during spring and summer, and the breakpoints both occurred in the 1980s. After the breakpoint, the mean biomass increased from 142.88 to 429.42 mg/m3 in spring and from 296.28 to 723.92 mg/m3 in summer. After 2000, the abundance of Copepoda in summer increased by more than 10 times compared to the 1960s. Under the conditions of warming and increased dinoflagellate abundance in the CJE, the abundance of the warm-water and omnivorous small calanoid copepod Paracalanus aculeatus increased significantly. Meanwhile, the significant decrease in the abundance of the temperate brackish species Labidocera euchaeta was probably mainly related to warming. The rapid changes in LMZ biomass during the late 1980s and mid-1990s is probably the result of a combination of enhanced bottom–up support, reduced top–down pressure, and promotion of temperature. This study provides scientific evidence and insights into the adaptive management of the Changjiang Basin.

Shrub layer structure and species diversity of warm temperate deciduous broadleaved forests of the Qinling Mountains Huangguan plot in China

Shrub is an important part of forest ecosystem. Exploring the species composition, structure and spatial distribution of shrub layer can lay an important foundation for further clarifying the mechanisms underlying species coexistence, biodiversity maintenance and community succession. In this study, species composition, spatial distribution, and species diversity of shrub layer were analyzed in 25 hm2 of Huangguan forest plot. A total of 20716 individual shrubs (with 10463 branches) were recorded in the plot, belonging to 54 species, 45 genera, 28 families. The status of dominant species in the shrub layer was not obvious, with all the importance values being less than 10. The diameter structure of shrub layer vegetation was inverted 'J' type. Shrubs showed aggregated distribution in the plot, with obvious altitude differences in spatial distribution. The diameter structure and spatial distribution of the nine shrub species with the largest abundance in the plot were consistent with the overall situation of shrub layer. With increasing altitude, the Shannon diversity index (H) and Simpson dominance index (D) did not change significantly, while the Pielou evenness index (E) decreased. Those indices decreased with the increases of the abundance of dominant species in tree layer, and E increased with the increase of the number of dominant species in sub-tree layer. The indices of H, D, E were significantly negatively correlated with soil total phosphorus (TP). The H index was significantly positively correlated with soil pH, and the E index was significantly positively correlated with soil total potassium. The shrub layer was rich in species, stable in community structure and well regenerated. The species diversity of shrub layer was mainly affected by the number of dominant species in the tree layer, soil pH, and TP.

Functional and taxonomic beta diversity of butterfly assemblages in an archipelago: relative importance of island characteristics, climate, and spatial factors

Islands host a disproportionate fraction of global biodiversity and provide ideal systems for investigating the factors affecting patterns of biodiversity. However, islands are also vulnerable systems and epicenters of biodiversity loss. Clarifying the processes that affect patterns of island biodiversity is important for achieving biodiversity conservation goals. Here, we studied the biodiversity of butterfly assemblages in Zhoushan Archipelago of China. Specifically, we evaluated i) whether functional and taxonomic beta diversity of butterfly communities provides complementary ecological insights; ii) the extent to which nestedness and turnover components contribute to total functional and taxonomic beta diversity; and iii) the relative contributions of island characteristics, spatial and climate factors to shaping functional and taxonomic beta diversity and its components. The contributions of the nestedness and turnover components to total taxonomic beta diversity were similar; by contrast, the relative contribution of the nestedness component to total functional beta diversity was much larger than that of the turnover component. A high nestedness component of both functional and taxonomic beta diversity reflected a nested spatial distribution of butterfly assemblages in Zhoushan Archipelago. Beta diversity decomposition and variation partitioning analysis (VPA) revealed that both functional and taxonomic beta diversity components provided complementary ecological insights. Taxonomic beta diversity and its turnover component were more strongly correlated with island isolation, while functional beta diversity and its turnover component were correlated more strongly with fine-scale spatial factors. VPA showed that island characteristics (e.g., perimeter-to-area ratio and isolation), climatic factors (e.g., temperature and precipitation), and broad-scale and some fine-scale spatial factors jointly contributed to shaping patterns of functional and taxonomic beta diversity of butterfly assemblages and their components. Lower functional beta diversity, especially low functional turnover, in our study indicated functional convergence. This was caused by the high abundance of dominant species. However, rare species can promote trait diversity, trait divergence, and convergence in functional biodiversity. Our study demonstrated that taxonomic and functional beta diversity can provide distinct insights into variation in butterfly communities. Island communities are affected by biogeographical, climate, and historical events. Studies of island communities that consider temporal variation in communities, including the effects of historical events, are needed to achieve a comprehensive understanding of patterns of biodiversity in island communities.