Structure Of Biological Communities Research Articles

Sea-ice properties and nutrient concentration as drivers of the taxonomic and trophic structure of high-Arctic protist and metazoan communities

In the Arctic Ocean, sea-ice decline will significantly change the structure of biological communities. At the same time, changing nutrient dynamics can have similarly strong and potentially interacting effects. To investigate the response of the taxonomic and trophic structure of planktonic and ice-associated communities to varying sea-ice properties and nutrient concentrations, we analysed four different communities sampled in the Eurasian Basin in summer 2012: (1) protists and (2) metazoans from the under-ice habitat, and (3) protists and (4) metazoans from the epipelagic habitat. The taxonomic composition of protist communities was characterised with 18S meta-barcoding. The taxonomic composition of metazoan communities was determined based on morphology. The analysis of environmental parameters identified (i) a ‘shelf-influenced’ regime with melting sea ice, high-silicate concentrations and low NOx (nitrate + nitrite) concentrations; (ii) a ‘Polar’ regime with low silicate concentrations and low NOx concentrations; and (iii) an ‘Atlantic’ regime with low silicate concentrations and high NOx concentrations. Multivariate analyses of combined bio-environmental datasets showed that taxonomic community structure primarily responded to the variability of sea-ice properties and hydrography across all four communities. Trophic community structure, however, responded significantly to NOx concentrations. In three of the four communities, the most heterotrophic trophic group significantly dominated in the NOx-poor shelf-influenced and Polar regimes compared to the NOx-rich Atlantic regime. The more heterotrophic, NOx-poor regimes were associated with lower productivity and carbon export than the NOx-rich Atlantic regime. For modelling future Arctic ecosystems, it is important to consider that taxonomic diversity can respond to different drivers than trophic diversity.

Traits Shared by Marine Megafauna and Their Relationships With Ecosystem Functions and Services

Traditional ecological research has focused on taxonomic units to better understand the role of organisms in marine ecosystems. This approach has significantly contributed to our understanding of how species interact with each other and with the physical environment and has led to relevant site-specific conservation strategies. However, this taxonomic-based approach can limit a mechanistic understanding of how environmental change affects marine megafauna, here defined as large fishes (e.g. shark, tuna, billfishes), sea turtles, marine mammals, and seabirds. Alternatively, an approach based on traits, i.e. measurable behavioural, physiological, or morphological characteristics of organisms, can shed new light on the processes influencing structure and functions of biological communities. Here we review 33 traits that are measurable and comparable among marine megafauna. The variability of these traits within the organisms considered controls functions mainly related to nutrient storage and transport, trophic-dynamic regulations of populations, and community shaping. To estimate the contributions of marine megafauna to ecosystem functions and services, traits can be quantified categorically or over a continuous scale, but the latter is preferred to make comparisons across groups. We argue that the most relevant traits to comparatively study marine megafauna groups are body size, body mass, dietary preference, feeding strategy, metabolic rate, and dispersal capacity. These traits can be used in combination with information on population abundances to predict how changes in the environment can affect community structure, ecosystem functioning, and ecosystem services.

Trait‐based approach confirms the importance of propagule limitation and assembly rules in old‐field restoration

Community assembly theory is suggested as a guiding principle for ecological restoration to help understand the mechanisms that structure biological communities and identify where restoration interventions are needed. We studied three hypotheses related to propagule limitation, stress‐dominance, and limiting similarity concepts in community assembly in a restoration field experiment with a trait‐based null model approach. The experiment aimed to assist the recovery of sand grassland on former arable land in the Kiskunság, Pannonian biogeographic region, Europe. Treatments included initial seeding of five grassland species, carbon amendment, low‐intensity mowing, and combinations in 1 m by 1 m plots in three old fields from 2003 to 2008. The distribution of 10 individual plant traits was compared to the null model and the effect of time and treatments were tested with linear mixed effect models. Initial seeding had the most visible impact on species and trait composition confirming propagule limitation in grassland recovery. Reducing nutrient availability through carbon amendment strengthened trait convergence for length of flowering as expected based on the stress‐dominance hypothesis. Mowing changed trait divergence to convergence for plant height with a strengthening impact with time, supporting our hypothesis of increasing dominance of limiting similarity with time. Our results support the idea that community assembly is simultaneously influenced by propagule limitation and multiple trait‐based processes that act through different traits. The limited impact of manipulating environmental filtering and limiting similarity compared to seeding, however, supports the view that only targeting the dispersal and environmental filters in parallel would improve restoration outcome.

Monsoon-influenced variations in plankton community structure and upper-water column stratification in the western Bay of Bengal during the past 80 ky

To enhance our understanding of the forcing factors of marine biological community structure in the Bay of Bengal, we studied proxies for biogenic carbonate and silicate production in the western Bay of Bengal and compared them with proxies for upper-ocean stratification and strength of the Indian summer monsoon (ISM). Specifically, we investigated the record in a sediment core from the western Bay of Bengal that extended to approximately 80 ky before the present (BP). The records of Globigerinoides ruber sensu stricto δ18O minus Neogloboquadrina dutertrei δ18O (Δδ18Or–d) were used to investigate changes in upper-ocean stratification. We reconstructed variations in mass accumulation rates (MARs) of CaCO3 and biogenic silica (BSi) to discuss plankton community structure. Greater difference between Globigerinoides ruber sensu stricto δ18O and Neogloboquadrina dutertrei δ18O during the marine isotope stage (MIS) 1 and 5a indicate intervals with less saline and more stratified conditions. In contrast, the relatively small difference between both planktic foraminiferal δ18O during MIS 2 and 4 indicates diminished stratification during these periods. Elevated carbonate production during MIS 2 and 4, demonstrated by the increase in CaCO3 MAR, could have been driven by lower freshwater influx to the western Bay of Bengal resulting from lower ISM precipitation, and thus the increased mixing and upwelling of deep nitrate into the photic zone. The relative increase in BSi MAR during periods of high ISM precipitation and decreased salinity of surface waters suggests a limited recovery in biological siliceous production under interglacial conditions, possibly due to enhanced fluvial SiO4 delivery to the ocean. Fluctuations of Δδ18Or–d during MIS 3 indicate that freshwater stratification was moderate and insufficient to restrict upwelling. This might have induced moderate biogenic silica and carbonate productions during this period.

海洋酸化对海洋鱼类行为的影响及机制研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 海洋酸化对海洋鱼类行为的影响及机制研究进展 DOI: 10.5846/stxb201807191556 作者: 作者单位: 农业部海洋渔业可持续发展重点实验室，中国水产科学研究院黄海水产研究所,浙江大学动物科学学院,农业部海洋渔业可持续发展重点实验室，中国水产科学研究院黄海水产研究所,农业部海洋渔业可持续发展重点实验室，中国水产科学研究院黄海水产研究所,农业部海洋渔业可持续发展重点实验室，中国水产科学研究院黄海水产研究所,农业部海洋渔业可持续发展重点实验室，中国水产科学研究院黄海水产研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中国博士后科学基金资助项目（2017M622323）；青岛海洋科学与技术国家实验室海洋生态与环境科学功能实验室创新团队项目（LMEES-CTSP-2018-4）；国家重点基础研究发展计划（2015CB453303） Effects and mechanisms of CO2-driven ocean acidification on marine fish behavior: A review Author: Affiliation: Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,College of Animal Sciences,Zhejiang University,Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Key Laboratory of Sustainable Development of Marine Fisheries,Ministry of Agriculture,Yellow Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:自工业革命以来，在人类活动的影响下，大气CO2浓度持续增加，其中有大约1/3被海洋吸收，造成海水pH值降低和碳酸盐平衡体系的波动，即"海洋酸化"现象（Ocean Acidification）。据联合国政府间气候变化专门委员会预测，如果以当前速率排放CO2，到21世纪末表层海水的pH值将降低至7.7-7.8，而到2300年将降低至7.3-7.4。作为鱼类对外界刺激最直接的反应，行为在鱼类的繁衍、捕食、避敌等过程中发挥着关键作用。基于此，海洋酸化对海洋鱼类行为的影响受到了越来越多关注。现有研究结果显示海洋酸化不仅会显著干扰包括嗅觉、听觉、视觉在内的感官功能，还将对神经生理功能和细胞信号传导等过程产生不利影响，从而影响海洋鱼类的捕食、逃避捕食、行为侧向化、栖息地识别与选择和集群等行为。行为异常将直接损害鱼类种群的生存与繁衍，继而威胁海洋生态系统的稳定和功能。我国海岸线漫长，海域辽阔，鱼类资源丰富，鱼类捕捞和养殖业发达。但与国外相比，国内此类研究十分匮乏，仅见零星报道。这种现状极大的制约了我国相关应对策略的制定，对我国海洋生态保育和渔业发展非常不利。此外，当前的研究也存在研究范围窄、研究手段不合理、行为效应、潜在机制及生态风险考察不足、研究结果难以整合等问题亟待改进。为此，研究对国内外相关研究进展进行了梳理和总结，并对未来的研究进行展望，以期弥补上述缺憾，促进国内相关研究的广泛开展。 Abstract:Since the industrial revolution, the atmospheric carbon dioxide (CO2) concentration has increased by approximately 40%, mainly due to anthropogenic activities (e.g., burning of fossil fuel). Approximately one third of CO2 released into the atmosphere is eventually absorbed by ocean, lowering the pH of surface seawater and causing wholesale shifts in seawater carbonate chemistry, a phenomenon known as "ocean acidification" (OA). During the past 250 years, the average surface seawater pH has decreased by approximately 0.1 units, from 8.21 to 8.10. According to the prediction of Intergovernmental Panel on Climate Change (IPCC), the average surface seawater pH will decline to 7.7-7.8 by the end of the 21st century and 7.3-7.4 around 2300. Behavior, the first response exhibited by fish to stimulus, plays important roles in fish reproduction, predation, and anti-predation. Therefore, effects of OA on marine fish behavior has, recently, garnered considerable attention and gradually become a new research hotspot. Although not immediately lethal, OA has been demonstrated to adversely influence marine fish behavior, especially their predation, anti-predation, behavioral lateralization, shoaling behavior, and habitat detection and seeking behavior, by disrupting sensory system, interfering with GABAA-receptor function, and hindering cell signal transduction. Behavior normality is likely to impair fitness and population survival, which will in turn affect species interactions and ecological processes, and subsequently pose a great threat to ecosystem structure and functioning. However, current knowledge on marine fish behavior modification is mostly obtained by laboratory simulation and restricted to single species, life stage, leading to an incomplete view of how OA and other coinciding environmental stressors can affect the ecological interactions that structure biological communities. More importantly, China has a long coastline, vast sea area, abundant fish resources, and developed fishing and aquaculture industry; however, only few studies in China have focused on fish behavior alteration under near future OA scenarios. These, undoubtedly, limit our ability to precisely forecast the potential risk of ecosystem in a rapidly changing marine environment, and deal with OA. We therefore reviewed published literature on marine fish behavior under OA conditions, synthesized current understanding and identified knowledge gaps of how OA might affect marine fish behavior, assessed the potential ecological risk, and discussed the underlying mechanisms. Finally, key suggestions have been provided to facilitate future studies, especially those in China. 参考文献 相似文献 引证文献

Spatial patterns of species richness and nestedness in ant assemblages along an elevational gradient in a Mediterranean mountain range.

BackgroundThe study of biodiversity spatial patterns along ecological gradients can serve to elucidate factors shaping biological community structure and predict ecosystem responses to global change. Ant assemblages are particularly interesting as study cases, because ant species play a key role in many ecosystem processes and have frequently been identified as useful bioindicators.MethodsHere we analyzed the response of ant species richness and assemblage composition across elevational gradients in Mediterranean grasslands and subsequently tested whether these responses were stable spatially and temporally. We sampled ant assemblages in two years (2014, 2015) in two mountain ranges (Guadarrama, Serrota) in Central Spain, along an elevational gradient ranging from 685 to 2390 m a.s.l.ResultsJackknife estimates of ant species richness ranged from three to 18.5 species and exhibited a hump-shaped relationship with elevation that peaked at mid-range values (1100–1400 m). This pattern was transferable temporally and spatially. Elevation was related to ant assemblage composition and facilitated separation of higher elevation assemblages (> 1700 m) from the remaining lower elevation species groups. Ant assemblages were nested; therefore species assemblages with a decreased number of species were a subset of the richer assemblages, although species turnover was more important than pure nestedness in all surveys. The degree of nestedness changed non-linearly as a cubic polynomial with elevation. These assembly patterns coincided more clearly over time than between the two study regions.DiscussionWe suggest double environmental stressors typical of Mediterranean mountains explained species richness patterns: drought at low elevations and cold temperatures at high elevations likely constrained richness at both extremes of elevational gradients. The fact that species turnover showed a dominant role over pure nestedness suggested current ant assemblages were context-dependent and highly vulnerable to global change, which threatens the conservation of present day native ant communities, particularly at high elevations.

Natural succession and clearcutting as drivers of environmental heterogeneity and beta diversity in North American boreal forests.

Clear-cutting alters natural ecosystem processes by reducing landscape heterogeneity. It is the dominant harvesting technique across the boreal zone, yet understanding of how environmental heterogeneity and beta diversity are structured in forest ecosystems and post-clear cut is lacking. We use ground-dwelling arthropods as models to determine how natural succession (progression from deciduous to mixed to coniferous cover types) and clear-cutting change boreal forests, exploring the role of environmental heterogeneity in shaping beta diversity across multiple spatial scales (between-cover types and between-stands of the same cover type (1600 to 8500 m), between-plots (100 to 400 m) and within-plots (20 to 40 m)). We characterise environmental heterogeneity as variability in combined structural, vegetational and soil parameters, and beta diversity, as variability in assemblage composition. Clear-cutting homogenised forest environments across all spatial scales, reducing total environmental heterogeneity by 35%. Arthropod beta diversity reflected these changes at larger scales suggesting that environmental heterogeneity is useful in explaining beta diversity both between-cover types and between-stands of the same cover type. However, at smaller scales, within- and between-plots spider beta diversity reflected the lower environmental heterogeneity in regenerating stands, whereas staphylinid and carabids assemblages were not homogenised 12 years post-harvest. Differences in environmental heterogeneity and staphylinid beta diversity between cover types were also important at small scales. In regenerating stands, we detected a subtle yet notable effect of pre-felling cover type on environmental heterogeneity and arthropods, where pre-felling cover type accounted for a significant amount of variance in beta diversity, indicating that biological legacies (e.g. soil pH reflecting pre-harvest conditions) may have a role in driving beta diversity even 12 years post-harvest. This study highlights the importance of understanding site history when predicting impacts of change in forest ecosystems. Further, to understand drivers of beta diversity we must identify biological legacies shaping community structure.

Effects of light intensity on oxygen distribution, lipid production and biological community of algal-bacterial granules in photo-sequencing batch reactors

The effects of light intensity (0–225 µmol m−2 s−1) on oxygen distribution, lipid production and biological community structure of algal-bacterial granules were investigated in six identical photo-sequencing batch reactors (with a dark/light cycle of 12 h/12 h). Typically green algal-bacterial granules could be developed at a light intensity of ≥135 µmol m−2 s−1. The lipid content was significantly increased under higher light intensity, while the percentage of saturated fatty acid methyl esters was remarkably decreased. Results showed that light intensity ≥90 µmol m−2 s−1 yielded enough O2 production from algae, creating aerobic/anoxic zone (0.3–0.6 mg-O2/L) in the core of granules and thus efficient algal-bacterial symbiosis system. Enhanced nitrogen and phosphorus removals were achieved in the reactors with stronger light illumination, probably attributable to the enrichment of ammonia oxidizing bacteria (Comamonadaceae and Nitrosomonadaceae) and algae (Navicula and Stigeoclonium). Illuminance ≥180 µmol m−2 s−1 was found to be unfavorable for Nitrospiraceae.

Decentralized economic dispatch of an isolated distributed generator network

A novel decentralized method for optimal load distribution in an isolated power system is proposed. In contrast to the traditional centralized method, the load economic dispatch is distributed to every smart distributed generator (DG) without the need for a monitoring host. Similar to the structure, mechanism and characteristics of biological communities, a smart DG node can communicate with adjacent nodes and operate collaboratively to complete the optimal operation of an isolated power system. The task is formulated as a decentralized optimization with a number of local constraints and is solved by a penalty function method. With the economic dispatch algorithm computed in all of the DG nodes in parallel, a new, fully distributed flat control network is established. The convergence property of the novel method is analysed theoretically. Simulation results on an illustrative system provide support for the validity of the proposed method.

Changes in the relationship between zooplankton and phytoplankton biomasses across a eutrophication gradient.

The relationship between zooplankton biomass and phytoplankton biomass can provide insight into the structure and function of lake biological communities. We used a Bayesian network model to analyze a continental-scale data dataset to estimate changes in the relationship between zooplankton (Z) and phytoplankton (P) biomasses along a eutrophication gradient. The Bayesian network model allowed us to combine two different measurements of phytoplankton biomass (chlorophyll a concentration and directly observed biovolume) to improve the precision of estimates of true biomass within each sample. The model also allowed us to estimate separate relationships between P and zooplankton abundance and between P and mean individual zooplankton biomass and then to combine these two relationships into an estimate of seasonal mean zooplankton biomass. The resulting analysis indicated that seasonal mean zooplankton biomass increased proportionally with phytoplankton biomass in oligotrophic lakes, yielding a constant ratio between Z and P and suggested that bottom-up forces determined zooplankton biomass in these systems. In eutrophic lakes, seasonal mean zooplankton biomass was nearly constant with increases in phytoplankton biomass, yielding a decrease in the ratio between Z and P with increasing eutrophication. Bottom-up forces, as quantified by an increase in the proportion of cyanobacteria, accounted for approximately one fifth of the residual variance in the model as the relationship between Z and P changed from direct proportionality in oligotrophic lakes to the nearly constant value of Z observed in eutrophic lakes, suggesting that a combination of both top-down and bottom-up forces likely determined zooplankton biomass in eutrophic lakes.

Response of soil aggregate-associated microbial and nematode communities to tea plantation age

Understanding the changes of soil microbial and nematode communities within aggregate fractions is essential for maintaining the stability of soil biological communities and soil health in agricultural ecosystems. However, the short- and long-term influence of converting abandoned land to tea (Camellia sinensis L.) plantations on soil aggregate-associated biological communities is still poorly understood. In this study, soil microbial and nematode communities were analyzed in soil fractions of different sizes collected from 0 to 20 cm depth in four tea plantations with the same plants (cultivar was “Sichuan tea”) of various ages (16-, 23-, 31-, and 53-years) in the hilly area of western Sichuan in China. The aggregates were separated by a dry-sieving procedure into four fractions: large (>2 mm), medium (2–1 mm), small (1–0.25 mm) macro-aggregates, and micro-aggregates (<0.25 mm). Although soil microbial biomass (bacteria, fungi, and actinomycetes) was not correlated (P > 0.05) with most nematode abundance (bacterivores, plant-parasites, fungivores, and omnivores and predators) across aggregate fractions in different tea plantation ages, not only microbial biomass and nematode abundance but also their diversity was highest in the large macro-aggregates, indicating that these fractions had a complex biological community structure with more connections in soil food web, thus providing biological buffering and prohibiting the dominance of individual organisms via competition or predation. In the process of tea cultivation, the abundance of soil nematodes was largely dependent on microbial biomass in the macro-aggregates where pore space was large enough for nematodes to prey on microbes, while there were no correlations (P > 0.05) between microbial biomass and nematode abundance in the micro-aggregates. The 23-year-old tea plantation provided a relatively stable soil environment for the development of microbial and nematode communities, and subsequently induced an increase of soil microbial biomass, nematode abundance, and their diversity. Notably, the degradation of soil biological communities after 23-years underscores the need for sustainable soil management practices that would maintain the stability of soil biological communities and soil health after 23-years of tea cultivation in the hilly area of western Sichuan in China.

Effects of Soil Residual Plastic Film on Soil Microbial Community Structure and Fertility

Plastic films have previously displayed tremendous potential to increase water use efficiency in farmland and the yield of cash crops; however, long-term use of plastic film in soils can influence soil physiological and biochemical characteristics and change its biota. The present study aimed to investigate the effects of residual plastic film pollution on soil microbe community structure and fertility in Xinjiang province, China. Residual plastic film-contaminated soil and non-contaminated soil in Xinjiang farmland were selected for this study. The results indicated that residual plastic film pollution changed the structure of the soil biological community by significantly decreasing and increasing the abundance of Actinomycetes and Proteobacteria, respectively; further, the pollution decreased soil organic matter and inorganic nitrogen content by downregulating microbial genes related to soil carbon and nitrogen cycles and decreasing related enzymatic activities. The present results indicated that long-term residual plastic film exposure (more than 10 years) in farmland significantly decreases soil fertility and alters the microbial community structure.

Do invasive exotic and native freshwater plant species respond similarly to low additional nitrate doses?

Nutrient status of freshwater ecosystems has a significant influence on biological invasions, species richness and community structure. The role of phosphorus in driving these effects has been widely reported while its co-limitation with nitrogen and other elements has received more recent attention. In a greenhouse experiment, we investigated the growth responses of two invasive exotic (Egeria densa and Salvinia molesta) and one native (Vallisneria spiralis) freshwater plant species to additional low concentrations of nitrate nitrogen (N-NO3). The species were grown at five nitrate concentrations (0.02, 0.05, 0.1, 0.5, and 0.9 mg N-NO3 L−1). We found that the growth of E. densa and V. spiralis increased with increasing nitrate concentration. Surprisingly, S. molesta had the fastest growth rate at the midrange nitrate concentration of 0.1 mg N-NO3 L−1 and its leaf production was not affected by nitrate treatment. Irrespective of nitrate concentration, the invasive exotic species, particularly S. molesta, showed much greater growth responses than the native V. spiralis. We conclude that freshwater plant growth responses to low nitrate concentrations will be species specific but the faster growth rates of S. molesta provide an example of how differences between co-occurring invasive exotic species and native species could have profound effects on the structure and function of freshwater ecosystems under changed environmental conditions.

Decentralized Optimization Algorithms for Variable Speed Pumps Operation Based on Local Interaction Game

A fully distributed optimal control strategy for the parallel variable speed pumps in heating, ventilation, and air-conditioning (HVAC) systems is proposed. Compared with the traditional centralized method, the efficient control and coordination are scattered to every updated smart pump without the need for a monitoring host. Similar to the structure, mechanism, and characteristics of biological communities, a smart pump can communicate with adjacent nodes and operate collaboratively to complete pumps group operation with the least total power consumption under load demand and system constraints. And a decentralized optimization method that is decentralized estimation of distribution algorithm (DEDA) under local interaction games framework has been transplanted to the proposed structure to optimize the pumps working in parallel mode. Besides, convergence property of the two novel mechanisms is analyzed theoretically. Finally, simulation studies have been conducted based on the models of a physical pumps system, and the performance of the proposed algorithm is compared with centralized algorithms in terms of both effectiveness and stability. The results provide support for the validity of the proposed algorithms and control structure.

Using the relationship between taxonomic and functional diversity to assess functional redundancy in streams of an altered tropical watershed

The relationship between taxonomic and functional diversity indices has been used to better describe and understand the structure of biological communities. Functional diversity is expected to have an asymptotic relationship with species richness because at some point, the addition of new species will increase some of the already established functional groups (functional redundancy). However, the asymptotic relationship may not be reached in intermediately disturbed systems once many intolerant species that would have played a redundant role or even represented some functional groups have been lost. This study aimed to address such a relationship (taxonomic and functional indices) and to evaluate the functional redundancy in intermediately disturbed streams in the Atlantic Rainforest domain. We expected a positive linear relationship between taxonomic and functional diversity; however, we did not expect to find an asymptotic relationship between richness and functional diversity because of the loss of many intolerant species caused by anthropogenic uses. The taxonomic diversity indices were Species Richness (SR) and Simpson’s Diversity (SD), while the functional diversity indices were the Functional Richness (FRic) and Functional Dispersion (FDisp). The two taxonomic and two functional diversity indices showed a significant positive relationship that never reached an asymptote, suggesting low functional redundancy in the fish communities. Our results indicate that care is needed in the management of the studied streams because assemblies with low functional redundancy are more susceptible to loss of functions in the case of species loss.

Phylogenetic structure of communities between temperate and tropical regions: Exploring patterns through literature datasets

Latitudinal patterns of diversity are one of the most striking large-scale biological phenomena and several hypotheses have been proposed to explain them. Using data from literature-surveys we investigated how phylogenetic patterns in microorganisms, plants, and, metazoans communities differ between the tropical and temperate regions and then explored possible ecological and evolutionary process that could shape such patterns. Using the Net Relatedness Index, we analyzed data from 1486 biological communities, collected in 32 articles that considered the phylogenetic structure of biological communities. We found a pattern of phylogenetic clustering in both regions for microorganisms, while for plants we found phylogenetic clustering in temperate regions and phylogenetic overdispersion in the tropics. We did not detect a clear pattern of clustering or overdispersion in tropical or temperate regions in metazoans. From these patterns we explore different ecological and evolutionary processes that have shaped these communities over space and time.

A decentralized sensor fault detection and self-repair method for HVAC systems

This study proposes a novel decentralized sensor fault detection and self-repair method for heating, ventilation and air-conditioning systems. From the perspective of network structure, sensor fault diagnosis in heating, ventilation and air-conditioning systems is distributed to the updated smart sensors without the monitoring host, which is necessary in the traditional centralized method. A fully distributed flat sensor network is established based on fundamental physical equations. Similar to the structure, mechanism and characteristics of biological communities, a smart sensor needs only to communicate with adjacent nodes and operate collaboratively to complete sensor fault detection and self-repair tasks. These tasks are formulated as a constrained optimization and are solved by a decentralized algorithm with a penalty function executed in all the sensor nodes in parallel. The diagnosis model introduces an exponential function method to determine the precise location and undertake self-repair of a fault node. Simulation results on a chilled water system illustrate the effectiveness of the proposed method. Practical application: The traditional sensor fault detection and diagnosis methods for heating, ventilation and air-conditioning systems are based on a centralized structure with several deficiencies, such as high maintenance and labor costs, link congestion and operational lag. This study presents a decentralized sensor network structure and exponential-function-based method that possess the advantages of plug-and-play, rapid deployment, high flexibility and convenience for engineering implementation without having to build a central monitor. The efficiency and effectiveness of the proposed method are demonstrated via a case study.

Cumulative ecological effects of a Neotropical reservoir cascade across multiple assemblages

Dams have altered the physiography and ecology of large rivers, causing severe environmental changes at a global scale. Assuming that series of reservoirs induce physical, chemical, and biological longitudinal changes in rivers, we tested the hypotheses that (i) the structure of biological communities in reservoir cascades is not only affected by changes in water quality, but also by cumulative hydrological alteration and impacts on river connectivity; and (ii) fish are more affected by cumulative effects of reservoirs when compared to other aquatic assemblages. Samplings of three assemblages (phytoplankton, benthic macroinvertebrates, and fish) were conducted in the reservoir cascade of Sao Francisco River, Brazil. We estimated the relative role of environmental and spatial predictors through variation partitioning analyses. Environmental variables, cumulative reservoir volume, longitudinal position, and distances from nearest reservoirs were used as explanatory variables. Environmental variables were the most important for the phytoplankton community. No significant effects of the predictors used were found for benthic macroinvertebrates, whereas spatial variables and cumulative reservoir volume were the most important predictors for fish. Therefore, our results provide evidence of impacts along reservoir cascades, and suggest that their effects mainly influence fish assemblages.

Nestedness in assemblages of helminth parasites of bats: a function of geography, environment, or host nestedness?

Nested subsets occur in ecological communities when species-poor communities are subsets of larger, species-rich communities. Understanding this pattern can help elucidate species colonization abilities, extinction risks, and general structuring of biological communities. Here, we evaluate nestedness in a poorly studied host-parasite system, bats and their helminths, across the Japanese archipelago and within its different bioclimatic regions. We hypothesized that (1) if helminth communities are nested across geographic sites at the level of the archipelago, then broad-scale processes, like colonization-extinction dynamics, mainly structure parasite assemblages; (2) if helminth communities are nested across geographic sites at the level of the bioclimatic region, then fine-scale environmental variation plays a significant role in species nestedness; (3) if helminth community nestedness mirrors host species nestedness, then communities are nested because the habitats they occupy are nested; and (4) if nestedness does not occur or if it is not correlated with any geographical or host data, then passive sampling could be responsible for the patterns of parasite assemblage in our sample. We found that helminth communities were nested across host species throughout the archipelago but, when considering each bioclimatic region, helminths in only one region were significantly more nested than the null model. Helminth communities were also nested across sites within all four bioclimatic regions. These results suggest that helminths form nested subsets across the archipelago due to broad-scale processes that reflect the overall lineages of their mammalian hosts; however, at the regional scale, environmental processes related to nestedness of their habitats drive parasite community nestedness.

Realized niches explain spatial gradients in seasonal abundance of phytoplankton groups in the South China Sea

A basic albeit elusive goal of ocean science is to predict the structure of biological communities from the multitude of environmental conditions they experience. Estimates of the realized niche-based traits (realized traits) of phytoplankton species or functional groups in temperate seas have shown that response traits can help reveal the mechanisms responsible for structuring phytoplankton communities, but such approaches have not been tested in tropical and subtropical marginal seas. Here, we used decadal-scale studies of pigment-based phytoplankton groups and environmental conditions in the South China Sea to test whether realized traits could explain the biogeographic patterns of phytoplankton variability. We estimated the mean and breadth of the phytoplankton realized niches based on responses of the group-specific phytoplankton composition to key environmental factors, and we showed that variations of major phytoplankton groups in this system can be explained by different adaptive trade-offs to constraints imposed by temperature, irradiance, and nutrient concentrations. Differences in the patterns of trade-offs clearly separated the dominant groups from one another and generated four sets of realized traits that mirrored the observed biogeographic distribution patterns. The phytoplankton realized niches and their associated traits that we characterized in the present study could help to predict responses of phytoplankton to changes in environmental conditions in the South China Sea and could be incorporated into global biogeochemical models to anticipate shifts in community structure under future climate scenarios.