Spatial and temporal variation in the macroinvertebrate community structure of the lower Elands River,Mpumalanga, South Africa

The Elands River, Mpumalanga, is an ecologically sensitive river that is constantly threatened by a variety of human activities. The influence of a pulp and paper mill on the river's macroinvertebrate assemblages was studied in March and June 2005, representing high- and low-flow seasons, respectively. Macroinvertebrates were collected from various biotopes using a standard sampling net, and were preserved and identified to family level. A range of multivariate and univariate statistical analyses was applied to assess the spatial and temporal variations in the macroinvertebrate communities. Diversity loss and dominance by a single taxon, Melanoides tuberculata, were noted directly below the mill. Other sites did not appear to be affected. Macroinvertebrate communities at all sites showed a strong seasonal variation.     

Optimising Bait for Pitfall Trapping of Amazonian Dung Beetles (Coleoptera: Scarabaeinae)

The accurate sampling of communities is vital to any investigation of ecological processes and biodiversity. Dung beetles have emerged as a widely used focal taxon in environmental studies and can be sampled quickly and inexpensively using baited pitfalls. Although there is now a wealth of available data on dung beetle communities from around the world, there is a lack of standardisation between sampling protocols for accurately sampling dung beetle communities. In particular, bait choice is often led by the idiosyncrasies of the researcher, logistic problems and the dung sources available, which leads to difficulties for inter-study comparisons. In general, human dung is the preferred choice, however, it is often in short supply, which can severely limit sampling effort. By contrast, pigs may produce up to 20 times the volume. We tested the ability of human and pig dung to attract a primary forest dung beetle assemblage, as well as three mixes of the two baits in different proportions. Analyses focussed on the comparability of sampling with pig or human-pig dung mixes with studies that have sampled using human dung. There were no significant differences between richness and abundance sampled by each bait. The assemblages sampled were remarkably consistent across baits, and ordination analyses showed that the assemblages sampled by mixed dung baits were not significantly different from that captured by pure human dung, with the assemblages sampled by 10% and 90% pig mixes structurally most similar to assemblages sampled by human dung. We suggest that a 10:90 human:pig ratio, or similar, is an ideal compromise between sampling efficiency, inter-study comparability and the availability of large quantities of bait for sampling Amazonian dung beetles. Assessing the comparability of assemblage samples collected using different baits represents an important step to facilitating large-scale meta-analyses of dung beetle assemblages collected using non-standard methodology.     

Putting bryophyte communities in the map: A case study on prioritizing monitoring of human pressure in riverscapes

Freshwater ecosystems support biological communities with high species richness and conservation interest. However, these ecosystems are highly altered by human intervention and threatened worldwide, making them a priority in conservation planning and biodiversity monitoring. Bryophytes, including several conservation-interest taxa, are recognized indicators of ecological status in freshwaters. We aimed to develop a framework for designing monitoring networks to detect trends in aquatic and semi-aquatic bryophyte communities, prioritizing high-conservation interest communities in different contexts of human pressure (specifically, resulting from the intersection of two criteria: (i) protection status and (ii) presence of a potential impact area).The framework consists of three steps: (1) Spatial modelling of biodiversity; (2) Spatial conservation prioritization; and (3) Model-assisted monitoring network design. Community-level modelling was used to model the distribution of the main bryophyte assemblages in the study area. A conservation prioritization software was utilized to identify areas with high conservation value. The monitoring network was designed using stratified random sampling and unequal-probability sampling techniques to target high conservation value sites distributed across different contexts of human pressure.We have identified four distinct community types, each characterized both by a small group of common and dominant species, and by small group of rarer, conservation-interest species. This typification of four species assemblages occurring in the study area, also highlighted those with potentially higher conservation-interest. The most valuable areas for the conservation of aquatic and semi-aquatic bryophyte communities coincide with specific environmental zones: mountainous areas in Lusitania, large watercourses in the Mediterranean North and some locations in the Mediterranean Mountains. Finally, we obtained a potential monitoring network consisting of 64 monitoring points, unequally distributed across different contexts of human pressure, privileging locations with higher conservation value.The framework presented here illustrates the potential of combining biodiversity modelling, spatial conservation prioritization and monitoring design in the development of monitoring networks. Namely, this framework allowed us to counter data deficiencies, to identify high priority areas to monitor and to design a monitoring network considering different scenarios of human pressure at a regional scale.This framework can also be valuable for conservation efforts as an approach to monitoring conservation-interest biodiversity features in anthropogenically modified riverscapes, which present different degrees of human pressure and the cumulative effects of these different impact elements. Moreover, this approach allows for the comprehensive monitoring of biodiversity values important for management at the national and regional levels. In addition, this framework is one of the first efforts in the development of monitoring networks that target aquatic and semi-aquatic bryophyte communities, a long-neglected plant group of high ecological and conservation importance in freshwater ecosystems.     

Phytoplankton Community Structure in the Drainage Network of a Mediterranean River System (Aliakmon,Greece)

Phytoplankton structure was studied in Aliakmon river basin in April (highflow) and September (lowflow) 1995 in 29 sampling sites. Abundance and biomass were generally low and ranged considerably between sites. Benthic diatoms contributed greatly to the suspended algal assemblages whereas trends of potamoplankton development were observed downstream. Limnoplankton and especially chlorophytes developed in the areas where lentic conditions prevailed. The nature of changes in phytoplankton seemed to be both longitudinal and temporal. Multivariate techniques revealed that areas with distinctive morphology, hydrology and anthropogenic inputs tended to have similar phytoplankton composition although no simple relation with physico-chemical factors can be shown. Human impact was more obvious on phytoplankton at the lowflow period. Generally, discharge played a significant role to the structure of phytoplankton communities.     

紫花针茅根际和体内真菌群落结构及与土壤环境因子的相关性研究

[目的] 探究青藏高原不同地区高寒草原紫花针茅根际和体内真菌群落的组成、多样性等特征,及与土壤环境因子（理化性质和酶活性）间的相互关系。[方法] 从青藏高原不同地区采集紫花针茅样品,应用土壤化学方法分析根际土壤理化性质和酶活性,并采用Illumina Miseq高通量测序技术,解析根际土壤和体内真菌群落组成和丰度、Alpha多样性和菌群结构,同时分析了紫花针茅根际真菌种群多样性与土壤环境因子的相关性,厘清了影响紫花针茅根际真菌区系的土壤环境因素。[结果] 三个采样地的根际土壤呈中性偏碱,土壤理化性质和酶活性变化各异。高通量测序共得到314801条有效序列和4491个OTUs;XZ样地的紫花针茅真菌多样性和丰富度相对偏低,GS样地最高。在门分类水平上,子囊菌门Ascomycota和担子菌门Basidiomycota是主要内生真菌类群,占总菌群的88.28%。不同采样地区紫花针茅体内真菌群落结构存在明显差异,而根际土壤真菌群落结构差异不大。相关性分析表明,紫花针茅真菌多样性与土壤pH、有效钾、铁、钙、镁、多酚氧化酶、过氧化物酶和脱氢酶呈显著（P<0.05）或极显著（P<0.01）正相关,而与海拔、土壤酸性磷酸酶呈极显著负相关。RDA分析发现,紫花针茅根际土壤真菌不同,影响的土壤环境因子也不同。[结论] 青藏高原高寒草地紫花针茅根际和体内栖息着丰富的真菌群落,其组成和多样性受多种土壤环境因子影响,且影响不同真菌群落的主要土壤环境因子也不同。本研究对于有益微生物资源的开发、利用及保护具有重要意义,并为紫花针茅草原保育和合理开发利用提供科学依据。     

Variation in the impact of non‐native seaweeds along gradients of habitat degradation: a meta‐analysis and an experimental test

Biological invasions are acknowledged among the main drivers of global changes in biodiversity. Despite compelling evidence of species interactions being strongly regulated by environmental conditions, there is a dearth of studies investigating how the effects of non‐native species vary among areas exposed to different anthropogenic pressures. Focusing on marine macroalgae, we performed a meta‐analysis to test whether and how the direction and magnitude of their effects on resident communities and species varies in relation to cumulative anthropogenic impact levels. The relationship between human impact levels and non‐native species impact intensity emerged only for a reduced subset of the response variables examined. Yet, there was a trend for the effects of non‐native species on community biomass and abundance and on species abundance to become less negative at heavily impacted sites. By contrast, the magnitude of negative effects of seaweed on community evenness tended to increase with human impact levels. The hypothesis of decreasing severity of invader’ impacts along a gradient of habitat degradation was also tested experimentally at a regional scale by comparing the effects of the removal of non‐native alga, Caulerpa cylindracea, on resident assemblages among rocky reefs exposed to different anthropogenic pressures. Assemblages at urban and pristine site did not differ when invaded, but did so when C. cylindracea was removed. Our results suggest that, despite the generally weak relationship between human impacts levels and non‐native species impacts, more negative impacts can be expected in less stressful environments (i.e. less degraded or pristine sites), where competitive interactions are presumably the driving force structuring resident communities. Implementing strategies for controlling the establishment of non‐native seaweeds should be, thus, considered a priority for preserving biodiversity in relatively pristine areas. On the other hand, control of invaders at degraded sites could be warranted to lessen their role as propagule sources. Synthesis Local anthropogenic stressors that severely alter biotic and abiotic conditions may underpin context‐dependency in the impacts of biological invasions. We used a meta‐analysis and an experimental test to examine the relationship between cumulative human impacts and ecological impact of non‐native seaweeds on resident assemblages. Our results suggest that more negative impacts of non‐native seaweeds on the abundance and biomass of resident assemblages can be expected in less degraded or pristine sites. Possibly, stronger impacts prevail at pristine sites, where assemblages are mainly structured by biotic interactions. Hence, management efforts should be mostly directed to prevent the establishment and spread of non‐native seaweeds in pristine areas. On the other hand, weak, but positive effects of seaweeds at the most degraded sites add to the ongoing debate on the role of non‐native species in rehabilitation plans.     

Distribution and Stability of Sulfate-Reducing Prokaryotic and Hydrogenotrophic Methanogenic Assemblages in Nutrient-Impacted Regions of the Florida Everglades

Although the influence of phosphorus loading on the Everglades ecosystem has received a great deal of attention, most research has targeted macro indicators, such as those based on vegetation or fauna, or chemical and physical parameters involved in biogeochemical cycles. Fewer studies have addressed the role of microorganisms, and these have mainly targeted gross informative parameters such as microbial biomass, enzymatic activities, and microbial enumerations. The objectives of this study were to characterize the dynamics of sulfate-reducing and methanogenic assemblages using terminal restriction fragment length polymorphism (T-RFLP) targeting the dissimilatory sulfite reductase (dsrA) and methyl coenzyme M reductase (mcrA) genes, respectively, and assess the impact of nutrient enrichment on microbial assemblages in the northern Everglades. T-RFLP combined with principal component analysis was a powerful technique to discriminate between soils from sites with eutrophic, transitional, and oligotrophic nutrient concentrations. dsrA T-RFLP provided a higher level of discrimination between the three sites. mcrA was a relatively weaker system to distinguish between sites, since it could not categorically discriminate between eutrophic and transition soil samples, but may be useful as an early indicator of phosphorus loading which is altering hydrogenotrophic methanogenic community in the transition zones, making them more similar to eutrophic zones. Clearly, targeting a combination of different microbial communities provides greater insight into the functioning of this ecosystem and provides useful information for understanding the relationship between eutrophication effects and microbial assemblages.     

How Much Is Too Little to Detect Impacts? A Case Study of a Nuclear Power Plant

Several approaches have been proposed to assess impacts on natural assemblages. Ideally, the potentially impacted site and multiple reference sites are sampled through time, before and after the impact. Often, however, the lack of information regarding the potential overall impact, the lack of knowledge about the environment in many regions worldwide, budgets constraints and the increasing dimensions of human activities compromise the reliability of the impact assessment. We evaluated the impact, if any, and its extent of a nuclear power plant effluent on sessile epibiota assemblages using a suitable and feasible sampling design with no ‘before’ data and budget and logistic constraints. Assemblages were sampled at multiple times and at increasing distances from the point of the discharge of the effluent. There was a clear and localized effect of the power plant effluent (up to 100 m from the point of the discharge). However, depending on the time of the year, the impact reaches up to 600 m. We found a significantly lower richness of taxa in the Effluent site when compared to other sites. Furthermore, at all times, the variability of assemblages near the discharge was also smaller than in other sites. Although the sampling design used here (in particular the number of replicates) did not allow an unambiguously evaluation of the full extent of the impact in relation to its intensity and temporal variability, the multiple temporal and spatial scales used allowed the detection of some differences in the intensity of the impact, depending on the time of sampling. Our findings greatly contribute to increase the knowledge on the effects of multiple stressors caused by the effluent of a power plant and also have important implications for management strategies and conservation ecology, in general.     

Fish assemblages associated with urban structures and natural reefs in Sydney,Australia

Abstract Fish ecology in urban estuaries is poorly understood. As coastal landscapes are transformed, recognizing the impact that urban structures, such as marinas, seawalls and wharfs, have on local fish populations is becoming increasingly important. The extent to which fish are able to maintain natural ecological assemblages can be measured, to a certain extent, by how closely they mimic natural habitats. In Sydney Harbour, assemblages of fish associated with artificial structures were compared with those associated with natural rocky reefs. Sampling was carried out in five locations, each with a marina, swimming enclosure and natural reef. In each location, different habitats supported different assemblages, but differences between habitats were not consistent among locations. Subsequent sampling compared artificial and natural sites in three different areas in each of three different estuaries. Results indicated that differences in fish assemblages between artificial and natural sites were greater than differences between sites within each habitat, but there were no patterns among different positions in an estuary or from estuary to estuary. This study provides initial evidence that, although artificial habitats generally support the same species as found on natural reefs, assemblages usually differed between natural and artificial habitats. In addition, without knowing if these habitats do, in fact, sustain viable populations of fish, it would be premature to label artificial structures as effective habitat for fish.     

Anthropogenic effect recorded in the live-dead compositional fidelity of land snail assemblages from San Salvador Island, Bahamas

Terrestrial malacofaunas that inhabit islands are vulnerable to human activities. Habitat destruction, introduction of exotic species, predators, etc. are distorting the composition and distribution of indigenous snail communities. Specifically, the taxonomic discordance between live and dead assemblages may be the consequence of anthropogenic disturbances rather than natural post-mortem processes. Live-dead fidelity may hence reflect the degree of human alteration in a given locality. This approach was used to study the relative abundance of live and dead land snails from pristine and urbanized localities around San Salvador Island (Bahamas). Thirteen species were encountered from 64 samples containing 5,343 specimens. Taxonomic composition was significantly different between areas of negligible anthropogenic disturbance and those impacted by humans. Although which species of land snails are endemic to San Salvador is unknown, all identified species are native to the Caribbean region and invasive species were not encountered. However, some synanthropic species, found exclusively in urban-developed areas, have not been recovered from the local fossil record, pointing to their relatively recent introduction possibly from nearby islands. Non-metric MDS, Jaccard-Chao index, and Spearman correlation analyses indicated that dead assemblages displayed a good compositional correspondence to live communities at pristine sites, whereas considerable disparity was sometimes observed at human-modified areas. Urbanized areas probably favored the proliferation of synanthropic species whereas dead assemblages may contain anthropophobic taxa that lived there prior to recent human modification. These findings are consistent with previous live-dead fidelity studies of marine molluscan and terrestrial small-mammal assemblages, and suggest that the taxonomic discordance between live and dead assemblages of land snails may be indicative of recent anthropogenic alteration.     

Rapid evaluation of threats to biodiversity: human footprint score and large vertebrate species responses in French Guiana

Although there is an extensive literature demonstrating the impact of human activities on both species extinction risk and local ecological processes, the methodological tools that allow for the visualization and quantification of the intensity of the observed and forthcoming impacts are lacking. Here we propose a Footprint index for French Guiana, (northern Atlantic coast of South America) which sums up the expected and proven disturbances on biodiversity. The index was developed by superimposing geographical and human data, including human population densities, land use, settlements and camps, mining and forest activities, tracks, roads and rivers. The relevance of the index as a general measure of anthropic impact on large terrestrial fauna was estimated by investigating the structure of the large terrestrial vertebrate assemblages, including primates, large frugivorous birds, rodents and ungulates, in relation to the extent of disturbances. The abundance of large terrestrial fauna was assessed using the line-transect sampling method in 34 forest sites facing different disturbance levels, including hunting, logging and fragmentation, and consequently different footprint scores. A Self Organizing Map was used to combine species abundances and disturbance scores. It allowed us to rank species in accordance to their sensitivity towards disturbances, identifying the response of fauna to different concomitant threats. The index provided correct identification of sites with similar threats which proves it is a relevant estimator of human disturbance. In addition, the richness of animal communities and abundances of several seed dispersers and predators were negatively correlated to the index (e.g. large monkeys and frugivorous birds, r ² = 0.49, P < 0.0001 and r ² = 0.48, P < 0.0001, respectively), indicating its reliability in identifying areas where animal communities are disturbed. The index could, therefore, constitute a useful tool to identify areas where ecological processes supported by those species are expected to be disrupted, and where they are already disrupted. Furthermore, the footprint index can deal with lack of field data or with only partially valid information, and so may directly help land managers forecast and, hopefully, mitigate forthcoming impacts resulting from the development of human activities.     

Changes in soil Acidobacteria communities after 2,4,6-trinitrotoluene contamination

Despite their widespread occurrence in soils, the ecology of Acidobacteria and their response to environmental perturbations due to human activities remain very poorly documented. This study was aimed at assessing changes in the diversity and abundance of Acidobacteria in soils contaminated with 2,4,6-trinitrotoluene (TNT) compared with nonpolluted soils. The analysis of Acidobacteria communities at two sites with long-term and short-term contamination revealed that TNT has a drastic impact on the relative abundance of Acidobacteria in soil bacterial 16S rRNA gene libraries. The disappearance of most Acidobacteria from these soils was concomitant with a shift in Acidobacteria community composition and a loss of diversity, although the extent of diversity erosion depended on the sampling site.     

Functional structure and specialization in three tropical plant–hummingbird interaction networks across an elevational gradient in Costa Rica

Understanding causes of variation in multispecies assemblages along spatial environmental gradients is a long‐standing research topic in ecology and biogeography. Ecological networks comprising interacting species of plants and pollinators are particularly suitable for testing effects of environmental gradients on the functional structure and specialization in multispecies assemblages. In this study, we investigated patterns in functional assemblage structure and specialization of hummingbirds at the individual and species level along a tropical elevational gradient. We mist‐netted hummingbirds at three elevations in Costa Rica in seven temporally distinct sampling periods and used the pollen carried by hummingbird individuals to construct plant–hummingbird networks at each elevation. We measured four functional traits of hummingbird species and quantified different metrics of functional community structure. We tested the effect of elevation on functional metrics of hummingbird assemblages and specialization within the networks, employing the variability across sampling periods and hummingbird species to compare the respective metrics among elevations. Hummingbird species and individuals were more specialized at low and mid elevations than at the highest elevation. This pattern corresponded to a more even and over‐dispersed assemblage structure at the lower elevations throughout the year and suggests a high level of floral resource partitioning in functionally diversified communities. In contrast, an uneven and clustered functional structure of the highland assemblage across all sampling periods suggests that this assemblage was structured by environmental filtering and by niche expansion of hummingbird individuals and species at this elevation. We conclude that high degrees of specialization on specific floral resources might be crucial for the coexistence of hummingbird species in diversified lowland communities. Spatial variation in animal resource use may be an important crucial driver of spatial patterns in the functional structure of diversified species assemblages also in other types of ecological networks.     

Structural and functional losses in macroalgal assemblages in a southeastern Brazilian bay over more than a decade

Changes in macroalgae assemblages over more than a decade are described for Sepetiba Bay, Brazil. Variations in macroalgae abundances and functional diversity were compared with older data to test the hypothesis that their diversity decreases following anthropogenic stress that negatively impact environmental characteristics. Four field sampling excursions were undertaken at two different sites from December/2012 to May/2014. Destructive sampling per effort used six box cores (25 × 25 cm) distributed randomly along a shallow sublittoral rocky shore. Biomass was used to quantify macroalgae assemblages identified to the species level. Multivariate analyses demonstrated decreases in total biomass at both sites as well as changes in community physiognomies. The predominant corticated algae found were classified as Ecological Status Group IIA, characteristic of sites in the process of degradation and indicating that anthropogenic stress had negatively affected the macroalgae communities as evaluated by the Ecological Evaluation Index.     

Predictive modelling of freshwater fish as a biomonitoring tool in New Zealand

SUMMARY 1. A challenge has been issued to ecologists to find quantitative ecological relationships that have predictive power. A predictive approach has been successful when applied to biomonitoring using stream invertebrates with the River Invertebrate Prediction and Classification System (RIVPACS). This approach, to our knowledge, has not been applied to freshwater fish assemblages.
2. This paper describes the initial results of the application of a regional predictive model of freshwater fish occurrence using 200 reference sites sampled in the Manawatu–Wanganui region of New Zealand over late summer/autumn 2000. In brief (i) sites were classified into biotic groups (ii) the physical and chemical characteristics that best describe variation among these groups were determined and (iii) the relationship between these environmental variables and fish communities was used to predict the fauna expected at a site.
3. Reference sites clustered into six groups based on fish density and community composition. Using 14 physical variables least influenced by human activities, a discriminant model allocated 70% of sites to the correct biological classification group. The variables that best separated the site groups were mainly large-scale variables including altitude, distance from the coast, lotic ecoregion and map co-ordinates.
4. The model was further validated by randomly removing 20% of the sites, rebuilding the model and then determining the number of removed sites correctly allocated to their original biotic groups using environmental variables. Using this process 67% of the removed sites were correctly reassigned to the six predetermined groups.
5. A further 30 sites were used to determine the ability of the model to detect anthropogenic impact. The observed over expected taxa ( O / E ) ratios were significantly lower than the reference site O / E ratios, indicating a response of the fish assemblages to the known stressors.     

High diversity of arbuscular mycorrhizal fungi in natural and anthropized sites of a Brazilian tropical dry forest (Caatinga)

Arbuscular mycorrhizal fungi (AMF) establish symbiotic associations with higher plants, which support the establishment and maintenance of plant communities across a range of environments, including those adversely affected by anthropogenic activity as well as natural sites. This study aimed at determining the diversity and distribution of AMF in areas of the tropical semi-arid region of Caatinga, Brazil, and compare areas in a naturally preserved state with anthropized sites. We characterized AMF communities in soil samples (n = 108), based on morphological taxonomy, at three sampling occasions and from six areas (typical Caatinga, extremely sandy Caatinga, stony Caatinga, rocky Caatinga, and two typical Caatinga areas that had been modified by human activities), at the National Park of Catimbau, Northeast Brazil. Eighty AMF species were recorded, with Glomus and Acaulospora predominating at all sites. There were significant differences in the composition of AMF communities between natural and anthropized sites, and among sampling occasions. Habitat-types also influenced AMF communities in Caatinga. Extensive tropical dry forest areas, such as the Catimbau National Park possess distinct niches, which maintain diverse AMF communities that are determined by anthropogenic activities, as well as vegetation types and environmental conditions.