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The first step in many community ecology studies is to produce a species list from a sample of individuals. Community ecologists now have two viable ways of producing a species list: morphological and barcode identification. In this study, we compared the taxonomic resolution gained by a combined use of both methods and tested whether a change in taxonomic resolution significantly impacted richness estimates for benthic macroinvertebrates sampled from ten lakes in Sequoia National Park, USA. Across all lakes, 77 unique taxa were identified and 42% (32) were reliably identified to species using both barcode and morphological identification. Of the 32 identified to species, 63% (20) were identified solely by comparing the barcode sequence from cytochrome oxidase I to the Barcode of Life reference library. The increased resolution using a combined identification approach compared to identifications based solely on morphology resulted in a significant increase in estimated richness within a lake at the order, family, genus and species levels of taxonomy ( P < 0.05). Additionally, young or damaged individuals that could not be identified using morphology were identified using their COI sequences to the genus or species level on average 75% of the time. Our results demonstrate that a combined identification approach improves accuracy of benthic macroinvertebrate species lists in alpine lakes and subsequent estimates of richness. We encourage the use of barcodes for identification purposes and specifically when morphology is insufficient, as in the case of damaged and early life stage specimens of benthic macroinvertebrates. [ABSTRACT FROM AUTHOR]

Ants and spiders are ubiquitous generalist predators that exert top-down control on herbivore populations. Research shows that intraguild interactions between ants and spiders can negatively affect spider populations, but there is a lack of long-term research documenting the strength of such interactions and the potentially different effects of ants on the diverse array of species in a spider assemblage. Similarly, the suitability of family-level surrogates for finding patterns revealed by species-level data (taxonomic sufficiency) has almost never been tested in spider assemblages. We present a long-term study in which we tested the impact of ants on the spider assemblage of a Mediterranean citrus grove by performing sequential 1-year experimental exclusions on tree canopies for 8 years. We found that ants had a widespread influence on the spider assemblage, although the effect was only evident in the last 5 years of the study. During those years, ants negatively affected many spiders, and effects were especially strong for sedentary spiders. Analyses at the family level also detected assemblage differences between treatments, but they concealed the different responses to ant exclusion shown by some related spider species. Our findings show that the effects of experimental manipulations in ecology can vary greatly over time and highlight the need for long-term studies to document species interactions. [ABSTRACT FROM AUTHOR]

Abstract: Since the introduction of ribonucleic acid gene restriction patterns as taxonomic tools in 1986, ribotyping has become an established method for systematics, epidemiological, ecological and population studies of microorganisms. In the last 25 years, several modifications have improved the convenience, reproducibility and turn-around time of this technique. The technological development culminated in the automation of ribotyping which allowed for high-throughput applications e.g. in the quality control of food production, pharmaceutical industry and culture collections. The capability of the fully automated RiboPrinter® System for the differentiation of bacteria below the species level is compared with the discriminatory power of traditional ribotyping, of molecular fingerprint techniques like PFGE, MLST and MLVA as well as of MALDI-TOF mass spectrometry. While automated RiboPrinting is advantageous with respect to standardization, ease and speed, PCR ribotyping has proved being a highly discriminatory, flexible, robust and cost-efficient routine technique which makes inter-laboratory comparison and build of ribotype databases possible, too. [Copyright &y& Elsevier]

Multimetric indices (MMIs) are routinely used by federal, state, and tribal entities to assess the quality of aquatic resources. Because of their diversity, abundance, ubiquity, and sensitivity to environmental stress, benthic macroinvertebrates are well suited for MMIs. West Virginia has used a statewide family-level stream condition index (WVSCI) since 2002. We describe the development, validation, and application of a geographically- and seasonally partitioned genus-level index of most probable stream status (GLIMPSS) for West Virginia wadeable streams. Natural classification strata were evaluated with reference site communities using mean similarity analysis and non-metric multidimensional scaling ordination. Forty-one metrics spanning six ecological categories (richness, composition, tolerance, dominance, trophic groups, and habits) were evaluated for sensitivity, responsiveness, redundancy, range and variability across seasonal (spring and summer) and regional (mountains and plateau) strata. Through a step-wise metric selection process, 8-10 metrics were aggregated to comprise four stratum-specific GLIMPSS models (mountain/plateau and spring/summer). A comparison of GLIMPSS with WVSCI exhibited marked improvements where GLIMPSS detecting greater stream impacts. A variation of the GLIMPSS, which differs only in the family-level taxonomic identification of Chironomidae (GLIMPSS (CF)), was comparable to the full GLIMPSS. These MMIs are robust yet practical tools for evaluating impacts to water quality, instream and riparian habitat, and aquatic wildlife in wadeable riffle-run streams based on sensitivity, responsiveness, precision, and independent validation. These models may be used effectively to detect degradation of the naturally occurring benthic community, assess causes of biological degradation, and plan and evaluate remediation of damaged stream ecosystems. [ABSTRACT FROM AUTHOR]

Aim Freshwater ecosystems are highly vulnerable to the effects of climate change. Where long-term datasets are available, shifts in species phenology, species distributions and community structure consistent with a climate change signal have already been observed. Identifying trends across the wider landscape, to guide management in response to this threat, is limited by the resolution of sampling. Standard biomonitoring of macroinvertebrates for water-quality purposes is currently not well suited to the detection of climate change effects, and there are risks that substantial changes will occur before a management response can be made. This study investigated whether dragonflies, frequently recommended as general indicators of ecological health, are also suitable as indicators of climate change. Location Data were analysed from standard bio-assessment monitoring at over 850 sites spanning a 9° latitudinal gradient in eastern Australia. Methods Using variation partitioning, we analysed the proportion of assemblage turnover in dragonflies and other macroinvertebrate assemblages that can be explained by climate and other environmental drivers. We also tested whether the utility of dragonflies as indicators improved at higher taxonomic resolution and whether the turnover of dragonfly assemblages was congruent with that of other groups. Results Climate explained three times as much variation in turnover of dragonfly species than dragonfly and other macroinvertebrate assemblages at family level. The dissimilarity of dragonflies and varying turnover in each macroinvertebrate assemblage meant surrogacy amongst groups were low. Main conclusions On the basis of the influence of climate on turnover of macroinvertebrate assemblages, dragonfly species distribution appears highly sensitive to climatic factors, making this taxon a potential useful indicator of climate change responses. However, the low surrogacy amongst assemblages also suggests that a shift in the focus of conservation management from specific taxa to the functional composition of assemblages across a diverse range of habitats is needed. [ABSTRACT FROM AUTHOR]

Taxonomic marker gene analysis allows uncovering taxonomic profiles of microbial communities at low cost, making it omnipresent in microbiome research. There is an ever-expanding set of tools to extract further biological information from this kind of data. In this perspective, we enunciate several concerns regarding the biological validity of predicting functional potential from taxonomic profiles, especially when they are generated by short-read sequencing. The taxonomic resolution of marker genes, intragenomic variability of marker genes, and the compositional nature of microbiome data are discussed. Combining actual measurements of microbiome functions with predicted functional potentials is proposed as a powerful approach to better understand microbiome functioning. In this context, the significance of predicted functional potentials for generating and testing hypotheses is highlighted. We argue that functions of microbiomes predicted from microbiome DNA read count data generated by short-read amplicon sequencing should not serve as the only basis to draw biological inferences., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors. iMeta published by John Wiley & Sons Australia, Ltd on behalf of iMeta Science.)

Abstract: According to the Water Framework Directive (WFD), the status of European surface waters is assessed using aquatic organism groups. Here we present an overview of 297 assessment methods, based on a questionnaire survey addressing authorities in all countries implementing the WFD. Twenty-eight countries reported on methods applied to rivers (30%), coastal waters (26%), lakes (25%) and transitional waters (19%). More than half of the methods are based on macroscopic plants (28%) or benthic invertebrates (26%); in addition, phytoplankton (21%), fish (15%) and phytobenthos (10%) were assessed. Countries of Central and Western Europe had developed almost all methods required for the WFD implementation. Two main sampling strategies were discernable: small-scale sampling of the taxonomically diverse groups of benthic invertebrates and phytobenthos that demand elaborate processing, versus large-scale sampling of vast, species-poor plant stands or the mobile fish fauna. About three-quarters of methods identified organisms to species-level while in particular phytoplankton-based methods used class- or phylum-level, or included no taxonomic information. Out of nine metric types distinguished, river methods used more sensitivity and trait metrics while for other water categories abundance metrics prevailed. Fish-based methods showed the highest number of metrics. Fifty-six percent of methods focussed on the detection of eutrophication and organic pollution, with shares decreasing from autotrophic to heterotrophic organism groups: phytoplankton>phytobenthos>macroscopic plants>benthic invertebrates>fish fauna. The order was almost reverse for hydrological or morphological deterioration: fish fauna and macroscopic plants>benthic invertebrates>phytoplankton>phytobenthos. These pressures were mainly assessed by methods applied to rivers and transitional waters. The pressure-impact relationship of about one-third of methods was not tested empirically with methods for transitional waters being the least validated. The strength of relationships differed significantly between organism groups and water categories. The correlation coefficients generally covered a broad range (<0.4 to >0.8), but on average with the pattern: phytoplankton>macroscopic plants>benthic invertebrates>phytobenthos and fish fauna. In terms of water categories the following order resulted: coastal waters>lakes>transitional waters>rivers. Status boundaries were mostly defined using statistical approaches. We advocate better reflection of the necessary sampling effort and precision, full validations of pressure-impact relationships and an implementation of more ecological components into classification. [Copyright &y& Elsevier]

Biodiversity assessments can often be time- and resource-consuming. Several alternative approaches have been proposed to reduce sampling efforts, including indicator taxa and surrogates. In this study, we examine the reliability of higher taxon surrogates to predict species richness in two experimental rice fields of Fujian Province, southeastern China during 2005 and 2009. Spider samples in transgenic and nontransgenic plots were collected using a suction sampler. Both the genus and family surrogates had significant and positive linear relationships with species richness in the transgenic and nontransgenic rice fields. The rice varieties did not significantly influence the linear relationships. Our findings suggest that higher-taxon surrogacy could be a useful alternative to complete species inventory for risk assessments of transgenic rice. [ABSTRACT FROM AUTHOR]

Processes occurring at the end of the larval stage are of major importance in shaping spatial structure of fish assemblages in coral reefs. However, because of the difficulty in identifying larvae to species, many studies dealing with these stages are limited to the family level. It remains unknown if variation in the spatial structure of coral-reef fish assemblages across life stages can be detected at such a coarse taxonomic level. Two different surveys conducted in a similar area of New Caledonia, Southwest Pacific, provided the opportunity to compare the structure of coral-reef fish assemblages collected as pre-settlement larvae, juveniles and adults along a coast to barrier reef gradient. Adult and juvenile fish were sampled using underwater visual counts (UVC) during the warm seasons of 2004 and 2005. Pre-settlement larvae were sampled with light-traps during the same seasons. In order to standardize data between sampling methods, analyses were conducted on the relative abundance (for larvae) and density (for juveniles and adults) of 21 families commonly collected with both methods. Relative abundances/densities of families were analysed as a function of life stage (larvae, juveniles or adults), large-scale spatial location (coast, lagoon or barrier) and years (2004, 2005) using non-parametric multidimensional scaling (nMDS) and permutational multivariate analysis of variance ( permanova). Kruskal-Wallis tests were then used to examine differences among life stages and locations for individual families. Different levels of spatial and temporal variability characterized fish assemblages from different life stages, and differences among life stages were detected at all locations and years. Differences among life stages were also significant at the level of individual families. Overall results indicate that studies conducted at the family level may efficiently reveal changes in coral-reef fish spatial structure among successive life stages when large spatial scales are considered. [ABSTRACT FROM AUTHOR]

Abstract: The analysis of sedimentary chironomid assemblages is an approach that has been widely adopted for inferring past environmental conditions. However, there is an ongoing discussion in the literature about whether this approach could become more sensitive at detecting past environmental changes if paleolimnologists conducted finer taxonomic analyses of their specimens. To advance this discussion, we conducted comparative analyses of larval chironomid assemblages resolved to two levels of taxonomic resolution. For this exercise, we chose to use live assemblages (as opposed to sub-fossil assemblages) because fine taxonomic resolution of live assemblages is more easily obtained. Our specific aims were to (i) determine if finely resolved taxa comprising a coarsely resolved group have similar ecological niches, (ii) determine if different environmental predictors of community composition are identified when two different levels of taxonomic resolution are applied and (iii) evaluate whether the variance explained by environmental variables differs substantially between levels of taxonomic resolution. We found that there was substantial dispersion among finely resolved taxa belonging to a single coarse group, which suggests that the merging of these taxa results in the loss of ecological information, and therefore warrants higher taxonomic precision. However, the identification of significant environmental predictors and the proportion of variance explained by these did not differ greatly between our two levels of taxonomic resolution. Overall our results show that coarse-resolution analyses may be adequate for some applications, but if the aim is to infer subtle environmental changes (as is the case in most paleolimnological studies) we recommend the highest possible level of taxonomic resolution. [Copyright &y& Elsevier]

Macrobenthic assemblages are widely used as a tool for ecological assessment studies and monitoring programs. However, studies of macrobenthic assemblages have been limited in tropical coastal and marine environments in comparison with those in temperate zones. This study characterized at different resolution of taxonomic levels the responses of macrobenthic assemblages inhabiting subtidal areas in Bahrain to sewage effluents and heavy metal contamination. Macrobenthic assemblages impacted by nutrient enrichment showed lower levels of biodiversity, richness and evenness, and higher degree of disturbance. Multivariate statistical analyses revealed that faunal patterns of species were sufficiently comparable to those of genus and family taxonomic levels and showed 98% and 95% similarity, respectively. Ammonia, phosphate, and depth were the main environmental parameters responsible for explaining 41% of the community patterns in the study areas. [ABSTRACT FROM AUTHOR]

Abstract: We assess the effects of taxonomic resolution (genus–family levels) on the ecological assessment of 39 highly heterogeneous ponds located in north-western Spain. Non-metric multidimensional scaling (MDS) and one-way analysis of similarities (ANOSIM) were used to investigate the effects of taxonomic resolution on the macroinvertebrate assemblage structure. The Mann Whitney U-test and discrimination efficiency were used to assess the ability of nine diversity measures (total richness, rarefied richness samples of 25, 50 and 100 individuals, Margalef''s index, Pielou''s evenness, Shannon–Weaver''s index, Simpson''s index and percent dominant taxon) to discriminate between acceptable (best available and good conditions) and unacceptable (moderate, poor and very poor) conditions using three levels of taxonomic resolution: (i) family, (ii) family plus subfamilies of benthic non-biting midges and (iii) genus level. Based on non-metric MDS, the macroinvertebrate assemblages of ponds of acceptable (A) and unacceptable (N) conditions were statistically undistinguishable, both at genus and family levels. On the other hand, based on several community metrics (total richness, Margalef index, etc.) the two sets of samples were statistically different, although only when the genus or the subfamily level was used and after Bonferroni correction. These results suggest that the structure of macroinvertebrate assemblages by itself is more sensitive than the specific composition in distinguishing the fauna living in acceptable and unacceptable conditions. Moreover, dealing with families including many taxa generally showing different tolerance to disturbance may lead to misclassification of ponds. We agree, however, that the two approaches, i.e. assemblage composition and diversity measures, are conceptually different and hence they should be used in combination for a better understanding of the response of single metrics. [Copyright &y& Elsevier]

1. Possible impacts of water-resource development on assemblages of freshwater macroinvertebrates were investigated in the upper Darling River and some of its tributaries in north-western New South Wales (Australia), an arid and semi-arid region of low relief where alteration of river flows has intensified through expansion of irrigated agriculture. 2. Study sites were grouped into four hydrological regimes resulting from impoundment, flow regulation, water abstraction and natural variation, namely (i) intermittent flow with relatively little hydrological alteration from water-resource development, (ii) intermittent flow with substantial alteration, (iii) near-perennial flow with substantial alteration but unimpounded and (iv) near-perennial flow with substantial alteration plus impoundment by weirs that stabilise water levels. 3. Macroinvertebrates were sampled with three methods (a quantitative cylinder sampler, handnet sampling and baited traps) in three periods with differing hydrology (recessional low flow in June 2003, high flow in March 2004 and increasing flow after drought in December 2004). 4. Taxonomic richness, assemblage composition and catch per unit effort of the crayfish Cherax destructor differed significantly among the site groups, but total macroinvertebrate density and the AUSRIVAS O/E (Australian River Assessment System observed-over-expected) index did not. The principal spatial differences were between the intermittent and near-perennial rivers, and apparent effects of water-resource development and impoundment were more subtle. Temporal differences in richness, abundance and composition were substantial and appeared to be related mainly to variations in discharge and temperature. 5. Current macroinvertebrate-based methods for assessing the ‘condition’ or ‘health’ of Australian dryland rivers are inadequate. Such assessments might be improved with (i) reference data that take adequate account of antecedent hydrological conditions, (ii) consideration of long-term taxonomic richness as well as richness on individual sampling occasions, (iii) evaluation of invertebrate population sizes, (iv) analysis of assemblage data by trait composition and (v) adoption of the genus as the default level of taxonomic resolution. [ABSTRACT FROM AUTHOR]

The resolution achievable for chironomid identifications has increased in recent years because of significant improvements in taxonomic literature. However, high taxonomic resolution requires more training for analysts. Furthermore, with greater taxonomic resolution, misidentifications and the number of rare, poorly represented taxa in chironomid calibration datasets may increase. We assessed the effects of various levels of taxonomic resolution on the performance of chironomid-based temperature inference models (transfer functions) and temperature reconstruction. A calibration dataset consisting of chironomid assemblage and temperature data from 100 lakes was examined at four levels of taxonomic detail. The coarsest taxonomic resolution primarily represented identifications to genus or suprageneric level. At the highest level of taxonomic resolution, identification to genus level was possible for 37% of taxa, and identification below genus was possible for 60% of taxa. Transfer functions were obtained using Weighted Averaging (WA) and Weighted Averaging-Partial Least Squares (WA-PLS) regression. Cross-validated performance statistics, such as the root mean square error of prediction (RMSEP) and the coefficient of determination ( r2) between inferred and observed values improved considerably from the lowest taxonomic resolution level (WA: RMSEP 1.91°C, r2 0.78; WA-PLS: RMSEP 1.59°C, r2 0.86) to the highest taxonomic resolution level (WA: RMSEP 1.66°C, r2 0.84; WA-PLS: RMSEP 1.41°C, r2 0.89). Reconstructed July air temperatures during the Lateglacial period based on fossil chironomid assemblages from Hijkermeer (The Netherlands) were similar for all levels of taxonomic resolution, except the coarsest level. At the coarsest taxonomic level, reconstruction failed to infer one of the known Lateglacial cold episodes in the record. Also, the difference in reconstructed values based on lowest and highest taxonomic resolutions exceeded sample-specific estimated standard errors of prediction in several instances. Our results suggest that chironomid-based transfer functions at the highest taxonomic resolution outperform models based on lower-resolution calibration data. However, transfer functions of intermediate taxonomic resolution produced results very similar to models based on high-resolution taxonomic data. In studies that include analysts with different levels of expertise, inference models based on intermediate taxonomic resolution, therefore, might provide an alternative to transfer functions of maximum taxonomic detail in order to ensure taxonomic consistency between calibration datasets and down-core records produced by different analysts. [ABSTRACT FROM AUTHOR]

Four arthropod datasets of different taxonomic detail were compared on their discriminatory power for various environmental characteristics in a lowland floodplain area along the river Rhine. The arthropod datasets comprised ground-dwelling arthropods at class-order level ( n = 10), beetle families ( n = 32), ground beetle genera ( n = 30) and ground beetle species ( n = 68). Environmental characteristics included vegetation characteristics, hydro-topographic setting, physical–chemical soil properties and soil contamination levels. Relations between arthropod assemblages and environmental factors were assessed with variance partitioning: a multivariate statistical approach that attributes variation in community composition to specific explaining variables. The variance partitioning showed comparable results for the four datasets. A substantial part of the variation (31–38%) could be ascribed to vegetation characteristics. Variance could further be attributed to physical–chemical soil properties (7–10%), hydro-topographic setting (3–7%) and soil metal contamination (2–4%). Thus, in strongly heterogeneous landscapes like lowland river floodplains, relatively coarse taxonomic data can already provide a valuable indication of the relative importance of different environmental factors for structuring arthropod communities. However, the ground beetles showed a higher specificity for different vegetation types and a more distinct relation to soil contamination levels than the other arthropod datasets. Hence, a higher degree of taxonomic detail will be beneficial for investigating the consequences of for example environmental pollution or vegetation characteristics in terms of taxonomic diversity or community composition. [ABSTRACT FROM AUTHOR]

The article present a study which determined whether intermediate or high taxonomic levels are good descriptors of community patterns and changes in assemblages related to harvesting on coral reef ecosystems. The authors found that for soft habitats, genus and family resolution allowed the detection of changes between exploited and protected assemblages. They say that the results show that the taxonomic sufficiency approach could be carefully applied to poorly known environments. The researchers believe that in detecting changes due to anthropogenic, different taxonomic resolutions are required depending on the considered habitat.

1 The effect of taxonomic level on the sensitivity of bioindicators has been widely investigated in aquatic ecosystems and, to a lesser extent, in terrestrial ecosystems. However, no studies have been conducted on the sensitivity of the different taxonomic levels of soil mites, especially Gamasina, to human activities. 2 The present study aimed to assess the sensitivity of different taxonomic levels of soil Gamasina mites to anthropogenic disturbances in Europe and Argentina. We arranged the data from previous projects in a hierarchical system and conducted a study to identify the critical taxonomical levels that had the highest discriminative potential between sites (Europe and Argentina) or management types (forests, grasslands, fallows, succession, recultivation and agricultural sites). 3 For the Gamasina community, geographical location was by far more important than the influence of any land use type. The analysis including only the European sites demonstrated that communities belonging to sites subjected to different land uses were also significantly different. 4 The species data set provided a clearer separation of sites according to both the geographical and the land-use gradients than the genus and family data sets. The genus and, to a lesser extent, the family approach may be sufficient to elucidate the influence of great geographical differences and also of certain land uses (e.g. grasslands from the forests and arable sites). 5 Species presence/absence data provided valuable information in our analyses, although the use of quantitative data yielded a clearer separation of sites. [ABSTRACT FROM AUTHOR]

Abstract: From December 2003 to November 2005, we analyzed the phytoplankton community of four streams located in Central Brazil (Goiás State) to evaluate if the temporal changes in phytoplankton community structure were dependent on the taxonomic/numerical resolution used to represent the data. Classification based on functional criteria was also contrasted with taxonomic classification to assess whether these classification schemes produce different ordination patterns. Procrustean analyses indicated that ordination patterns generated with data based on the presence or absence of genera correlated significantly with the patterns generated by species density. Temporal trajectories of scores derived from functional groups significantly matched those derived from analyses based on quantitative data (density or biovolume) for genus or family. In general, the results indicated that some simplifications are justifiable, mainly when one takes into account the need for uninterrupted biomonitoring programs over large spatial scales in a continent-sized country with increasing environmental problems and with a relative paucity of scientists. [Copyright &y& Elsevier]

Aim To investigate taxonomic homogenization and/or differentiation of insect and vascular plant assemblages across the Southern Ocean Islands (SOI), and how they differ with changing spatial extent and taxonomic resolution. Location Twenty-two islands located across the Southern Ocean, further subdivided into five island biogeographical provinces. These islands are used because comprehensive data on both indigenous and non-indigenous insect and plant species are available. Methods An existing database was updated, using newly published species records, identifying the indigenous and non-indigenous insect and vascular plant species recorded for each island. Homogenization and differentiation were measured using Jaccard’s index (JI) of similarity for assemblages across all islands on a pairwise basis, and for island pairs within each of the biogeographical provinces. The effects of taxonomic resolution (species, genus, family) and distance on levels of homogenization or differentiation were examined. To explore further the patterns of similarity among islands for each of the taxa and groupings (indigenous and non-indigenous), islands were clustered based on JI similarity matrices and using group averaging. Results Across the SOI, insect assemblages have become homogenized (0.7% increase in similarity at species level) while plant assemblages have become differentiated at genus and species levels. Homogenization was recorded only when pairwise distances among islands exceeded 3000 km for insect assemblages, but distances had to exceed 10,000 km for plant assemblages. Widely distributed non-indigenous plant species tend to have wider distributions across the SOI than do their insect counterparts, and this is also true of the indigenous species. Main conclusions Insect assemblages across the SOI have become homogenized as a consequence of the establishment of non-indigenous species, while plant assemblages have become more differentiated. The likely reason is that indigenous plant assemblages are more similar across the SOI than are insect assemblages, which show greater regionalization. Thus, although a suite of widespread, typically European, weedy, non-indigenous plant species has established on many islands, the outcome has largely been differentiation. Because further introductions of insects and vascular plants are probable as climates warm across the region, the patterns documented here are likely to change through time. [ABSTRACT FROM AUTHOR]

The study presented here searched for the level of taxonomic resolution required to detect the effects of low-level chronic pollution on estuarine meiobenthic communities. Meiofauna from two sites, with special attention to harpacticoid copepods, was analysed at different taxonomic levels of aggregation using uni- and multivariate methods. Adaptation processes that could buffer biodiversity disruptions were also considered through the analysis of fitness-related and tolerance traits in the harpacticoid copepod Paronychocamptus nanus. Results showed that uni- and multivariate analyses could be inadequate when assessing subtle anthropogenic contamination. Instead, the assessment of inter-population differences in tolerance to the main source of stress rises as a required procedure if potential effects of this type of contamination are being investigated. Specifically, a 96 h acute toxicity test performed with populations from the affected site appears as a faster and reliable general tool to assess impacts of low-level chronic pollution in estuaries. [Copyright &y& Elsevier]

The article presents a research on the effectiveness of higher taxa of macroinvertebrates as surrogate for species in the selection of conservation reserves in estuaries in south-east Australia. The research shows that the difficulty of identifying several macroinvertebrates to the order level diminishes the performance of order as surrogate for species richness. It also suggests that genus- and family-level identification is an effective surrogate for conservation planning in estuaries.

1. The δ13C and δ15N signatures of zooplankton vary with dissolved organic carbon (DOC), but inconsistent and limited taxonomic resolution of previous studies have masked differences that may exist among orders, genera or species and are attributable to dietary and/or habitat differences. Here we investigate differences among the isotopic signatures of five zooplankton taxa ( Daphnia, Holopedium, large Calanoida, small Calanoida and Cyclopoida) in Precambrian shield lakes with a sixfold range of DOC concentration. 2. δ13C signatures of Daphnia, small calanoids and large calanoids became more depleted with increasing lake DOC, whereas Holopedium and cyclopoid δ13C became enriched with increasing DOC concentration. 3. The variability of δ13C and δ15N isotopic signatures among zooplankton groups was reduced in high-DOC, compared to low-DOC lakes, especially for δ13C. Differences in δ13C and POM-corrected δ15N accounted for up to 33.7% and 19.5% of the variance, respectively, among lakes of varying DOC concentration. 4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and/or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and/or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change. [ABSTRACT FROM AUTHOR]

The effects of taxonomic resolution on the variance estimates of macrobenthic assemblages were studied at four spatial scales in a Mediterranean coastal lagoon. The assemblages exhibited significant differences at all the investigated scales; however, spatial variability was mainly associated with the smallest and the largest scales. The decrease of taxonomic resolution (from species to family) was not related to a decrease of the overall variability and similar estimates of variance components were obtained using species and family resolution levels. The ordination models derived from species and family abundances were very similar both in terms of location and dispersion effect, while further aggregation to the class level began to alter the observed spatial patterns. In future studies aimed at assessing changes in the lagoon, resources derived from the cost reductions achieved using family level could be employed to plan more frequent surveys and/or to adopt complex spatial sampling designs with a high number of replicates. [Copyright &y& Elsevier]

New land uses can drive complex changes to local biodiversity. In the Northeastern U.S., cultivated milkweed has arisen as a new crop with potentially promising outcomes for monarch butterflies, but has unknown effects on surface-active and soil-dwelling arthropods. We assessed differences in arthropod communities among nearby sites containing milkweed and three common regional land uses: conventional corn, conventional hay, and forest, representing a spectrum of high to low land use intensity. In each land use, we sampled surface-active and soil-dwelling arthropods, and we classified organisms at the taxonomic order level for all collected arthropods and at the taxonomic genus level for surface-active beetles. To address differences in functional traits between sites, we measured organisms' body sizes and calculated average body mass, total biomass, and abundance of arthropods in small, medium, and large size classes. In almost all analyses, taxonomic diversity values were significantly higher in the milkweed site than in corn and similar between the milkweed and hay sites. Milkweed had significantly higher diversity of surface-active arthropods than forest (for both orders and beetle genera), but did not have higher diversity of soil-dwelling arthropods, indicating possible different mechanisms driving aboveground versus belowground trends. Community composition differed significantly among land uses (demonstrated in NMDS ordination plots), with milkweed most similar to hay. Body size analyses demonstrated high total biomass and generally higher abundance of larger individuals in milkweed than in other land uses, with the exception of corn, which was dominated by large carabid beetles. We discuss the implications of our findings to land use properties and ecological function. Our case study indicates promising benefits of milkweed cultivation for soil biodiversity and soil health, with more research needed to validate and build from our results. • Milkweed cultivation is a novel land use in the northeastern United States. • We surveyed soil arthropods in cultivated milkweed, corn, hay, and forest. • Milkweed had consistently high diversity of arthropod orders and beetle genera. • Community composition and body size distributions were unique in each land use. • Milkweed cultivation has promising ecological benefits. [ABSTRACT FROM AUTHOR]

• Taxonomic and numerical resolution of datasets varies in biomonitoring studies. • Satisfactory surrogacy between metabarcoding and morphology-based datasets. • Community-environmental associations were significant for all datasets. • Coarser taxonomic resolution is advantageous to metabarcoding-based applications. • Metabarcoding reveals changes in communities in response to river restoration. It is essential to explore and define the level of taxonomic identification and quantification approaches for diversity and biomonitoring studies, given their potential influence on assessing and interpreting ecological outcomes. This study assessed the response of benthic macroinvertebrate communities to restore and construct gravel bars in a dam-impacted river, with non-dam influenced tributaries serving as reference sites. Additionally, we evaluated the performance of different taxonomic and numerical (i.e., abundance vs. presence/absence data) resolutions of DNA metabarcoding with consequent comparison to morphology-based identification and how it affects assessment outcomes. DNA metabarcoding detected 93% of the morphologically identified individuals and provided finer taxonomic resolution. We also detected significant correlations between morphological sample abundance, biomass, and DNA metabarcoding-read abundance. Furthermore, we observed a relatively high and significant congruence in macroinvertebrate community structure and composition between different taxonomic and numerical resolutions of both methods. This indicates a satisfactory surrogacy between the two approaches and their varying identification levels and data transformation. Additionally, community–environmental associations were significant for all datasets but showed significant varying associations with physicochemical parameters. Our observations imply that coarser taxonomic resolution could be highly advantageous for DNA metabarcoding-based applications in situations where the lack of taxonomic information, e.g., poor reference database, might severely affect biological assessment quality. [ABSTRACT FROM AUTHOR]

This paper examines how the use of various taxonomic levels and morphological functional groups influences the interpretation of multivariate analyses when comparing macroalgal assemblages in different regions in the Northeast Pacific. We found that for intertidal assemblages, within-site variation was high at the species level and regions only became discernable from the genus level to the order level. Above order level, regions were less well distinguished. Differentiating assemblages at the genus level were similar to results from functional group analyses. This implies that various levels and morphological functional groups can be used to distinguish intertidal assemblages among regions. Intertidal strata differences could be discerned at all taxonomic levels and using functional groups. In contrast to the intertidal, only a few regions were significantly different for subtidal assemblages, independent of taxonomic resolution used. Functional grouping in subtidal assemblages yielded the same resolution as taxonomic levels. Conversely to the intertidal assemblages, strata differences in the subtidal were found at the species and genus levels and with functional groups but not at the family and higher levels. Overall, these results demonstrate differences in regional and strata comparisons in intertidal and subtidal assemblage analyses and that typically species-level analyses are not required. [ABSTRACT FROM AUTHOR]

Nested systems of biodiversity classification are commonly used for designating protected area networks in terrestrial and marine realms. Whilst terrestrial-style protected areas are largely inappropriate for freshwater systems, the concepts of ‘representative’ biodiversity and ‘complementarity’ can be borrowed for freshwater conservation. Cryptic species are commonly found in freshwater macroinvertebrates and fish, and most have restricted distributions relative to the described conglomerate ‘species’. This indicates that ‘representative’ and therefore ‘complementary’ units of freshwater biodiversity may be smaller than previously appreciated. Using recently detected cryptic species in atyid shrimps from eastern Australia (Atyidae: Paratya australiensis, Caridina mccullochi and C. indistinca), we tested predictions about regional patterns of cryptic assemblage structure, endemism and Phylogenetic Diversity (PD) at the river scale, and discussed their implications for freshwater conservation. Patterns of distribution in these cryptic shrimp species largely corresponded with published distributional patterns of cryptic species in several freshwater fish in eastern Australia, and indicated the presence of four putative ecoregions within a previously recognised freshwater fish province (Eastern Province). However, some rivers had pronounced cryptic endemism, suggesting that rivers may not be ‘representative’ of one another’s biodiversity even within ecoregions. PD and endemism were largely correlated with one another, as endemics typically co-occurred with widespread species at the river scale. This study indicates that cryptic species can contribute to defining patterns of biodiversity at nested spatial scales that may be important for freshwater conservation. [Copyright &y& Elsevier]

Abstract: The Water Framework and Habitats Directives require the evaluation of both the conservation and ecological status of macroalgae communities at water body or habitat level. However, assessments of macroalgal communities are highly time-consuming, both in terms of sampling effort and laboratory processing. These constraints have brought about their oversight in many marine monitoring programs, especially in subtidal environments. By using data from intertidal and subtidal macroalgae assemblages of Mouro Island (North coast of Spain) we wanted to identify possible cost-effective methods for monitoring this biological indicator, based on both high taxa levels and use of representative taxa. Multivariate analyses were applied using different data transformations. The results show that macroalgal communities are robust to aggregation to genus or even family level. Moreover, the outcomes show that transformation types introduce higher variation in the multivariate pattern of samples than the taxonomic level to which organisms are identified. Also, the study supports the use of representative taxa as a surrogate to overall community structure. Therefore, we conclude that a rapid-assessment by means of field evaluations, based on coverage of representative taxa, is a reliable alternative for the assessment of macroalgae status. In addition this procedure allows evaluation at a broader spatial scale (water body or habitat level) than traditional quantitative sampling procedure does. [Copyright &y& Elsevier]

Abstract: Environmental assessment at the community level in highly diverse ecosystems is limited by taxonomic constraints and statistical methods requiring true replicates. Our objective was to show how diverse systems can be studied at the community level using higher taxa as biodiversity surrogates, and re-sampling methods to allow comparisons. To illustrate this we compared the abundance, richness, evenness and diversity of the litter fauna in a pine-oak forest in central Mexico among seasons, sites and collecting methods. We also assessed changes in the abundance of trophic guilds and evaluated the relationships between community parameters and litter attributes. With the direct search method we observed differences in the rate of taxa accumulation between sites. Bootstrap analysis showed that abundance varied significantly between seasons and sampling methods, but not between sites. In contrast, diversity and evenness were significantly higher at the managed than at the non-managed site. Tree regression models show that abundance varied mainly between seasons, whereas taxa richness was affected by litter attributes (composition and moisture content). The abundance of trophic guilds varied among methods and seasons, but overall we found that parasitoids, predators and detrivores decreased under management. Therefore, although our results suggest that management has positive effects on the richness and diversity of litter fauna, the analysis of trophic guilds revealed a contrasting story. Our results indicate that functional groups and re-sampling methods may be used as tools for describing community patterns in highly diverse systems. Also, the higher taxa surrogacy could be seen as a preliminary approach when it is not possible to identify the specimens at a low taxonomic level in a reasonable period of time and in a context of limited financial resources, but further studies are needed to test whether the results are specific to a system or whether they are general with regards to land management. [Copyright &y& Elsevier]

Summary: Using pitfall traps, we evaluated the spatial and seasonal variance in arthropod abundance, species richness, higher taxonomic and species composition, and guild structure within the ground litter of seven sites in a relatively undisturbed rainforest in Panama. We examined each of these five arthropod-dependent variables at two spatial scales (a few meters and a few hundred meters) and one temporal scale (a few months encompassing dry and wet periods), against environmental variables including local illumination and plant composition. Trap catches (9458 arthropods collected during 630 trap-days) were high compared to similar studies in temperate forests. We observed spatial and seasonal differences in abundance, species richness and composition of litter-dwelling arthropods. Often these differences appeared weakly related to geographical coordinates. They reflected forest structure (basal area) and local plant composition, and less so illumination patterns or seasonal changes in radiation. Seasonal variance was high and may relate to surrogate variables accounting for seasonal changes in litter moisture. The composition of higher taxa and species was often predicted by different independent variables at the three scales studied. Guild structure was difficult to predict. Our study lead us to expect that litter-dwelling arthropods may be more seasonal than soil microarthropods in tropical rainforests; and that tropical litter-dwelling arthropods may also be more spatially variable and seasonal than their temperate counterparts. We also recommend that conservation studies using pitfall traps in tropical rainforests should focus on: (1) taxonomic resolution to understand the functional complexity of soil organisms; (2) spatial replication to address subtle changes in plant composition throughout the study area; and (3) seasonal replicates to be commensurate with seasonal changes in litter moisture. [Copyright &y& Elsevier]

Diatoms are useful indicators of aquatic conditions, and metrics based on published autecological indicator values have been developed utilizing their sensitivities to various ambient physical and chemical conditions. The autecological values often differ within genera, and indeed within species taxonomic levels, requiring identification to subspecies taxonomic level for accurate application. This study was conducted to determine if autecological metrics, and ultimately indices of biotic integrity, could be developed using mean autecological values at the genus, species, and subspecies taxonomic levels, and to investigate the potential benefits of increased taxonomic resolution. Sixty-nine isolated herbaceous wetlands in various land use modalities in peninsular Florida were sampled a single time for epiphytic diatoms, and soil/water physicochemical parameters. Thirty genera, 148 species, and 26 subspecies were identified. The proportional matrices at each taxonomic level were highly similar (Mantel’s r > 0.75, P < 0.0001). Autecological metrics and two sensitive or tolerant measures were developed at each taxonomic level. Wetland condition, as determined by summed metric values, was strongly correlated across taxonomic level ( r 2 > 0.83, P < 0.0001), and no significant difference was found when sites were placed into bins of excellent, good, fair, or poor, based on quartile scoring, for each taxonomic level. Specific conductance, soil pH, soil and water total phosphorous, and water color were significantly related to site non-metric multidimensional scaling (NMDS) ordination scores at each taxonomic level. This study concludes that indices of biotic integrity, when developed using autecological indices, provide similar qualitative conditional information across taxonomic levels for isolated herbaceous wetlands. [ABSTRACT FROM AUTHOR]

1. We studied chironomid communities of four rivers in south-eastern Finland, differing in their water quality, during summer 2004 using the Chironomid Pupal Exuvial Technique, CPET. The aims of the study were to (i) test the adequacy of the generic-level identification in the CPET method, (ii) define the emergence patterns of chironomid taxa classified as intolerant to organic pollution, (iii) assess the tolerance levels of intolerant chironomids and (iv) identify taxa most indicative of good water quality. 2. Procrustean rotation analysis indicated very strong concordance between the ordinations using either species or genus-level data, suggesting that generic-level identification of chironomids is adequate for biomonitoring based on CPET. However, when only a few taxa occur in great numbers, it may be advisable to identify these to the species level, especially if these taxa are important indicators of the impact in question. 3. The detection of a particular species may require accurate timing of sampling, whereas a species-rich genus might be detected throughout a season. Given that the emergence of chironomid species may vary from year-to-year and between sampling sites, community differences detected at the species level may be related to between-site variation in species’ emergence patterns rather than true differences in species composition. 4. Indicator species analysis (IndVal) showed that the distribution and abundance of intolerant chironomid taxa differed strongly among the studied rivers. Some of the intolerant taxa were restricted to unimpacted conditions, whereas others occurred mainly in impacted rivers. Thus, the indicator status of some genera (e.g. Eukiefferiella, Parametriocnemus, Stempellinella and Tvetenia) needs reassessment. [ABSTRACT FROM AUTHOR]

In studies using macroinvertebrates as indicators for monitoring rivers and streams, species level identifications in comparison with lower resolution identifications can have greater information content and result in more reliable site classifications and better capacity to discriminate between sites, yet many such programmes identify specimens to the resolution of family rather than species. This is often because it is cheaper to obtain family level data than species level data. Choice of appropriate taxonomic resolution is a compromise between the cost of obtaining data at high taxonomic resolutions and the loss of information at lower resolutions. Optimum taxonomic resolution should be determined by the information required to address programme objectives. Costs saved in identifying macroinvertebrates to family level may not be justified if family level data can not give the answers required and expending the extra cost to obtain species level data may not be warranted if cheaper family level data retains sufficient information to meet objectives. We investigated the influence of taxonomic resolution and sample quantification (abundance vs. presence/absence) on the representation of aquatic macroinvertebrate species assemblage patterns and species richness estimates. The study was conducted in a physically harsh dryland river system (Condamine-Balonne River system, located in south-western Queensland, Australia), characterised by low macroinvertebrate diversity. Our 29 study sites covered a wide geographic range and a diversity of lotic conditions and this was reflected by differences between sites in macroinvertebrate assemblage composition and richness. The usefulness of expending the extra cost necessary to identify macroinvertebrates to species was quantified via the benefits this higher resolution data offered in its capacity to discriminate between sites and give accurate estimates of site species richness. We found that very little information (<6%) was lost by identifying taxa to family (or genus), as opposed to species, and that quantifying the abundance of taxa provided greater resolution for pattern interpretation than simply noting their presence/absence. Species richness was very well represented by genus, family and order richness, so that each of these could be used as surrogates of species richness if, for example, surveying to identify diversity hot-spots. It is suggested that sharing of common ecological responses among species within higher taxonomic units is the most plausible mechanism for the results. Based on a cost/benefit analysis, family level abundance data is recommended as the best resolution for resolving patterns in macroinvertebrate assemblages in this system. The relevance of these findings are discussed in the context of other low diversity, harsh, dryland river systems. [ABSTRACT FROM AUTHOR]

Patterns of spatial autocorrelation of biota may reveal much about underlying ecological and biological forces responsible for generating the patterns. Operationally, ecological work and many applied problems (e.g., impact detection, ecosystem health assessment using reference sites) require statistical knowledge of autocorrelation patterns. Here, we report on assemblage-level autocorrelation in the benthic-invertebrate assemblages of riffles in two adjacent, relatively pristine rivers in south-eastern Victoria, Australia (40 km reaches of the Wellington and Wonnangatta rivers). The assemblages of the Wellington River were strongly autocorrelated, but those of the Wonnangatta River showed a distance-independent pattern. There was no effect of taxonomic resolution, rarity protocols or whole-assemblage surrogates on the inferred levels of autocorrelation. We conclude that there is little evidence that one can assume the pattern of spatial relationships among invertebrate faunas within a river, and this probably holds true for the usual set of taxonomic resolutions and subsets used to discern changes wrought by human impacts. [ABSTRACT FROM AUTHOR]

Abstract: The long-term effects of marine aggregate dredging on near-shore benthic assemblages are still largely unknown, despite a global increase in demand for, and extraction of, marine aggregates. This study assessed the state of recovery of polychaete assemblages in Botany Bay, temperate NSW, Australia, at sites dredged for aggregate material more than 10years previously. Sedimentary and faunal samples were collected from impact sites in Botany Bay, and from reference sites in nearby Pittwater estuary. This study was based on, and included data from, a study conducted by the Australian Museum at the same sites in the 2years following cessation of dredging. Abundance, species richness and evenness of polychaetes, as well as overall polychaete assemblage structure, were compared between localities over time. [Copyright &y& Elsevier]

In the EU water framework directive (WFD) a typological framework is defined for assessing the ecological quality of water bodies in the future. The aim of this study was to test the effect of data composition and taxonomic resolution on this typology. The EU research projects AQEM and STAR provided 1660 samples of 48 stream types sampled all over the major geographical gradients in Europe. These stream types fit the WFD typological demands and fit to the major European geographic regions (ecoregions). The samples included gradients from reference conditions to samples with bad ecological quality. Despite standardisation, there were large differences between the participating countries concerning the number of taxa, the number of specimens, and the taxonomic resolution. The macroinvertebrate data were analysed by using detrended correspondence analysis (DCA). The distribution patterns using all samples, only reference samples, and only degraded samples showed that the use of species-level (or ‘best available taxonomic’ level) performed better at a practical (fine) scale in comparison to family-level. The analyses further showed that even the use of a standardised protocol can not easily overcome (i) differences in site conditions that force the researcher to deviate from the protocol as well as (ii) the experiences of the researcher(s) and (iii) the available taxonomic knowledge. [ABSTRACT FROM AUTHOR]

Abstract: Given the logistical difficulties, cost, and time involved in species-level identifications, several authors have proposed the use of coarser taxonomic resolution (e.g. family, order) in studies of pollution. The use of surrogates instead of species relies on their sufficiency to detect community responses to the pollution gradient without appreciable loss of information. No studies, however, have applied this approach to experimental studies such as community responses to predation disturbance and evaluated the performance of surrogates at the spatial scales typical of experiments. We addressed both problems by analyzing the results of three predation experiments carried out in Bonne Bay, Newfoundland. We pooled species data into coarser taxonomic categories (family to class) and determined whether effects of predation that were evident at the species level were also evident with the use of each coarser surrogate and increasing data transformation. Our results indicate that non-transformed data at the family level represent a reasonable surrogate of species; however, the ability to discriminate between ambient and (predator) manipulated sediments is gradually lost with data transformation and with the pooling of species into coarser taxonomic categories. Successive data transformation indicates that in this system predation plays a strong role on dominant but not necessarily rare species. Moreover, our results suggest that varying reliability of surrogates precludes the identification of a single general level of taxonomic sufficiency to be used in experimental studies. The use of surrogates, therefore, is suggested only after scrutiny and evaluation, and should be limited to preliminary studies where biodiversity has been well described. [Copyright &y& Elsevier]

1 Species-level pollen identifications within the genera Acer, Fraxinus and Juglans have the potential to increase the detail available from regional- and landscape-scale studies of palaeo-forest dynamics. 2 Data from the North American Pollen Database (NAPD) and the North American Modern Pollen Database (NAMPD) for sites in eastern North America for which species-level identifications have been recorded enabled us to consider pollen taxonomy at high resolution. 3 Species within each of Acer, Fraxinus and Juglans have important differences in habitat, functional type and responses to climatic change. Analysis of the modern distribution of these taxa and their pollen rains confirms that species-level pollen identifications provide detailed ecological information, but the lack of distinction to the species level in many fossil and modern pollen studies renders palaeoenvironmental reconstructions incomplete. 4 Within each of three selected high-resolution sites, ordinations indicate that individual species of Acer, Fraxinus and Juglans follow different trajectories through the Holocene, showing that analysing only generic categories results in the loss of ecologically valuable information. For example, pollen of Acer rubrum increased in abundance in response to canopy openings in a southern Ontario forest around 500 years ago, while that of A. saccharum declined. Similarly, Juglans nigra pollen percentages increased while J. cinerea decreased at this time. 5 Regional-scale comparisons of pollen percentage curves indicate that, despite the uncertainties associated with the low temporal resolution and the chronologies, it is reasonable to conclude that individual species of Acer, Fraxinus and Juglans responded synchronously to palaeoclimatic changes within each region. 6 Taking analyses to the specific level shows that different species followed different tracks in their post-glacial history, a fact previously blurred by less resolved taxonomy. This information is meaningful in biogeographical terms, providing much more specific evidence of how the selected trees behaved in the past. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the combined effects of decreasing taxonomic resolution (i.e. species, family, phylum), the use of different mesh-size (1.0mm and 0.5mm) and the type of samplers used (van Veen vs. corers taken by divers) on the quality of data obtained, a comparative study was undertaken with the overall aim of identifying cost efficient methods for routinely monitoring the ecological change caused by Mediterranean fish farming. The results clearly showed that information loss was relatively low as data were aggregated at higher taxonomic levels, particularly up to the level of family or even order. It was also found that the extra information gained by sieving samples through a 0.5mm sieve did not improve the ability to distinguish the potentially impacted sites from the control stations. Finally, it was found that a relatively large proportion of the available information concerning the community structure such as abundance, biomass or diversity is lost when sampling is carried out with corers. A cost/benefit ratio analysis for the two sampling and the two sieving methods showed minimal values for the van Veen samples (for both sieve fractions) at the family level, indicating that analysis at this level gives the best balance between precision of the results and decrease in taxonomic effort. However, if the time needed to sort the samples is included in the analysis, then samples taken with corers using a 0.5mm sieve and identified to families seems like a good compromise between precision and cost. [Copyright &y& Elsevier]

The taxonomic sufficiency approach has been proposed as a surrogate for the typical analysis of speciesabundance data, especially in conditions involving prominent pollution gradients. Here, we evaluate the use of taxonomic sufficiency with infralittoral macrobenthic data derived from samples taken in a moderate polluted subtropical environment in southeastern Brazil, analysing five taxonomic levels and including two functional levels throughout polychaete feeding guilds and trophic groups. The data were collected seasonally at nine stations and studied for two abundance data series (0.5 and 1.0 mm sieve mesh-size). The results showed a similar ordination pattern between the two sieve mesh-size, but with the 0.5 mm sieve data a different pattern was observed during austral summer. A slight loss of information was detected using genus, family, polychaete species and their feeding guilds as taxonomic/ functional units. These results together with those of the cost/ benefit ratio, suggested that the family level seemed to be sufficient to detect the impact caused by moderate pollution in this shallow-water, subtropical environment. In additional, through the use of feeding guilds, similar patterns are obtained. Correlation analysis showed that chlorophyll a, total organic matter, zinc, and chromium sediment content were the variables that best explained the biological pattern observed and not always the best correlation coefficient occurring at the species level. The feeding guild approach seems to be useful and generates interpretable results similar to those obtained with the species level of the whole macroinfauna. The results showed an important cost reduction in the sample processing, suggesting that it is possible to adopt a coarser taxonomic level monitoring program even in species-rich communities. [ABSTRACT FROM AUTHOR]

This article discusses the appropriate role for natural field experiments in ecology. At one extreme is the argument that experiments are always the preferred way to carry out ecological research, while at the other extreme is the assertion that classical experimentation in ecology is essentially impossible. As with most such debates the truth is probably somewhere in the middle, and even those who champion the experimental approach would concede that the application of standard experimental-design principles to ecology is often exceedingly difficult. For example, due to the scale at which ecosystem processes operate, true replication rarely exists. Furthermore, because many of the factors affecting ecosystems are non-manipulable, the standard strategy of randomization to equalize treatment and control groups is generally not available. These same difficulties also occur in the design of ecological impact studies, but there are additional complications. In natural experiments the assignment of an impact to a site is typically not under the control of the researcher and the simultaneous imposition of impacts on suitable replicate sites rarely occurs.

This study investigated the structure and properties of a tropical stream food web in a small spatial scale, characterizing its planktonic, epiphytic and benthic compartments. The study was carried out in the Potreirinho Creek, a second-order stream located in the south-east of Brazil. Some attributes of the three subwebs and of the conglomerate food web, composed by the trophic links of the three compartments plus the fish species, were determined. Among compartments, the food webs showed considerable variation in structure. The epiphytic food web was consistently more complex than the planktonic and benthic webs. The values of number of species, number of links and maximum food chain length were significantly higher in the epiphytic compartment than in the other two. Otherwise, the connectance was significantly lower in epiphyton. The significant differences of most food web parameters were determined by the increase in the number of trophic species, represented mainly by basal and intermediate species. High species richness, detritus-based system and high degree of omnivory characterized the stream food web studied. The aquatic macrophytes probably provide a substratum more stable and structurally complex than the sediment. We suggest that the greater species richness and trophic complexity in the epiphytic subweb might be due to the higher degree of habitat complexity supported by macrophyte substrate. Despite differences observed in the structure of the three subwebs, they are highly connected by trophic interactions, mainly by fishes. The high degree of fish omnivory associated with their movements at different spatial scales suggests that these animals have a significant role in the food web dynamic of Potreirinho Creek. This interface between macrophytes and the interconnections resultant from fish foraging, diluted the compartmentalization of the Potreirinho food web. [ABSTRACT FROM AUTHOR]

1. During late spring 1993–1995, the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) sampled 490 wadeable streams in the mid-Atlantic Highlands (MAH) of the U.S. for a variety of physical, chemical and biological indicators of environmental condition. We used the resulting data set to evaluate the importance of differing levels of macroinvertebrate taxonomic resolution in bioassessments by comparing the ability of family versus genus to detect differences among sites classified by type and magnitude of human impact and by stream size. We divided the MAH into two physiographic regions: the Appalachian Plateau where mine drainage (MD) and acidic deposition are major stressors, and the Ridge and Valley where nutrient enrichment is a major stressor. Stream sites were classified into three or four impact classes based on water chemistry and habitat. We used stream order (first to third Strahler order) in each region as a measure of stream size. Ordination, 2 × 2 chi-square and biotic metrics were used to compare the ability of family and genus to detect differences among both stressor and size classes. 2. With one notable exception, there were only a small number of different genera per family (interquartile range = 1–4). Family Chironomidae, however, contained 123 different genera. As a result, significant information loss occurred when this group was only classified to family. The family Chironomidae did not discriminate among the predefined classes but many chironomid genera did: by chi-square analysis, 10 and 28 chironomid genera were significant in discriminating MD and nutrient impacts, respectively. 3. Family and genus data were similar in their ability to distinguish among the coarse impacts (e.g. most severe versus least severe impact classes) for all cases. Though genus data in many cases distinguished the subtler differences (e.g. mixed/moderate impacts versus high or low impacts) better than family, differences in significance levels between family and genus analyses were relatively minor. However, genus data detected differences among stream orders in ordination analyses that were not revealed at the family level. In the ordinations, both family and genus levels of analysis responded to similar suites of environmental variables. 4. Our results suggest that identification to the family level is sufficient for many bioassessment purposes. However, identifications to genus do provide more information in genera-rich families like Chironomidae. Genus or finer levels of identification are important for investigating natural history, stream ecology, biodiversity and indicator species. Decisions about the taxonomic level of identification need to be study specific and depend on available resources (cost) and study objectives. [ABSTRACT FROM AUTHOR]