Using fuzzy‐coded traits to elucidate the non‐random role of anthropogenic stress in the functional homogenisation of invertebrate assemblages

相似文献   

Environmental predictability of taxonomic and functional community composition in high‐latitude streams

相似文献   

Patterns of macroinvertebrate traits along three glacial stream continuums

1. Glacier‐fed streams are characterised by low spatial but high temporal heterogeneity, manifested in seasonal and diurnal discharge and suspended sediment peaks induced by glacial runoff. These streams shelter macroinvertebrate communities adapted to such harsh environmental conditions. Studies relating macroinvertebrate traits to environmental conditions in glacial streams could provide important insights into the structure and function of glacial stream communities. 2. From data collected in three glacial streams from the central Swiss and southern French Alps, we analysed the relationships among six biological traits to define five groups of macroinvertebrate taxa with similar suites of traits. 3. The longitudinal distribution of the five groups and of individual traits was analysed, as well as their variation according to a glaciality index combining water temperature, conductivity, suspended solids and substrate stability. 4. The trait diversity along the three streams showed a strong upstream‐downstream gradient. The upper reaches were dominated by a single group of taxa characterised by small, crawling, deposit feeders. The other trait‐based groups appeared progressively downstream. 5. Changes in the relative frequency of trait‐based groups along the glaciality gradient highlighted the dominance of all‐rounder resistant/resilient traits in the three streams and confirmed that environmental conditions in the glacial streams are too harsh or uniform to allow macroinvertebrate communities to develop alternative suites of traits. The findings are discussed in relation to the question of trait coding in the available literature.     

Synthesising the trait information of European Chironomidae (Insecta: Diptera): Towards a new database

Chironomidae are among the most conspicuous and ecological diverse group of freshwater invertebrates. They may dominate unimpacted communities in abundance and biomass, accounting for more than 50% of macroinvertebrate species in standing and flowing waters. In deep zones of eutrophic lakes and highly human-impacted streams, they are often the only family of aquatic insects remaining. In bioassessment programmes, Chironomids are often identified at the family and subfamily levels, due to difficulties in the taxonomic identification of larvae resulting from a high intrinsic morphological similarity. This may potentially result in bias as, similarly to Ephemeroptera, Trichoptera or Plecoptera, Chironomidae species, which are replaced along natural and human-impacted gradients due to differences in their ecological requirements. Recently, multiple trait-based approaches have been proposed to complement taxonomic-based assessment of streams and rivers using macroinvertebrates. However, the lack of specific trait information for Chironomidae prevents their use in the functional assessment of communities. Therefore, here, we aimed to: (1) develop a trait database for European Chironomidae genera that can be used in future bioassessment and ecological studies; (2) evaluate, by multivariate analyses, whether our new database provides additional information on Chironomidae compared to the trait information provided in the commonly used European trait database (Tachet et al., 2010); and (3) determine whether the new information on Eltonian traits (proxy to biological traits) translates the most accepted phylogenetic relationships among Chironomidae subfamilies. We gathered information on 744 species and 178 genera, for 37 traits covering 186 trait categories, and found substantial differences between our database and the commonly used European trait database. In addition, available information on traits was not always in agreement with phylogenetic relationships among subfamilies. Orthocladiinae and Chironominae which are considered sister groups in evolutionary terms actually showed confident trait relatedness based on Eltonian traits tree while the remaining relationships between subfamilies are questionable. In addition, different traits can occur in closely related taxa depending on the environmental drivers operating on their habitats. Our study reveals that the usually accepted redundancy within the Chironomidae family and subfamilies must be a product of averaging the information from finer taxonomic resolution added to the substantial lack of information for this insect group.     

Effects of land cover type on community structure and functional traits of alpine stream benthic macroinvertebrates

1. In the European Alps, due to the current changes in land use driven by different social and economic factors, grasslands and pastures are being increasingly replaced by forests. Whereas many studies have focused on the impacts of urbanisation and intensive agricultural activities, no study has evaluated the effects of changes among types of natural to semi-natural land cover in the Alps with a focus on lotic environments.
2. Here, combining taxonomic and functional approaches, we show the effects of four different alpine land cover types (rocks, grasslands, coniferous forests, valley bottom pastures) on stream benthic macroinvertebrate communities. Irrespective of elevation, grasslands and pastures exhibited unpredicted similarity in terms of the composition of the macroinvertebrate assemblages and hosted the highest diversity of benthic organisms, whereas in each of the other land cover types, the density and diversity of the faunal assemblages showed distinct and characteristic values.
3. When analysing the functional diversity decomposed to richness, evenness, and divergence components, grasslands and pastures again showed a similar trend, being characterised by high levels of resource exploitation and niche differentiation, with the potential to host additional organisms. However, as expected, differences driven by land cover type and elevation emerged when examining the single functional traits, since elevation played a major role in terms of the distribution of traits conferring resistance and resilience.
4. Our results demonstrate that land cover type is a prominent factor influencing the taxonomic and functional variety of stream benthic macroinvertebrate communities. Moreover, alpine grasslands contained an unexpected diversity of aquatic insects, as previously assessed for other organisms (e.g. plants and snails). Overall, our study highlights the importance of the preservation of the diversity of habitats in the alpine region, with a special focus needed for valuable semi-natural landscapes, such as grasslands and pastures, particularly in a time of increasing intensification and abandonment of lands in the alpine context.

     

Functional classifications and their application in phytoplankton ecology

相似文献   

Taxonomic and functional homogenisation of macroinvertebrate communities in recently intermittent Alpine watercourses

1. Mountain streams in southwestern European Alps are currently shifting from perennial to intermittent flow due to the combined effects of climate change and local anthropogenic pressures. Given that flow intermittency is a recently documented phenomenon in the Alps, only scattered studies have investigated functional and taxonomical diversity of benthic invertebrate communities in recently intermittent Alpine streams.
2. We used a hierarchical sampling design to investigate patterns in taxonomic and functional diversity of benthic invertebrate communities in 13 recently intermittent Alpine streams in north-west Italy. in April 2017, we sampled benthic communities in two reaches of each stream with different hydrological conditions: a control reach, with permanent flow; and an intermittent reach, which recently experienced non-flow periods in summer.
3. We tested for the response of taxonomic richness at multiple spatial scales by partitioning total diversity into the average richness of local communities and the richness due to variation among local communities both within and among reaches. By partitioning total diversity (γ) into its local (α) and turnover (β) components we showed a decrease in local and regional species richness both within and among reaches, whereas variation among communities was significantly lower in intermittent reaches at the reach scale only.
4. The analysis of multidimensional trait space of macroinvertebrate communities in reaches with different hydrological conditions revealed a significant reduction of functional diversity, dispersion, and evenness in intermittent reaches. There was trait overdispersion in intermittent reaches, as these hosted both typical Alpine taxa and organisms adapted to flow intermittency. In particular, we observed the replacement of taxa with aquatic respiration and those preferring medium- to fast-flowing oligotrophic waters by taxa adapted to lentic habitats, air breathing and with larval dormancy phases.
5. These results indicate that recent flow intermittency has caused drastic changes in benthic invertebrate communities in Alpine streams. Our work highlights the importance of integrating taxonomic and functional diversity to thoroughly assess the impacts of flow intermittency.

     

Theoretical habitat templets, species traits, and species richness: Trichoptera in the Upper Rhône River and its floodplain

• 1 For Trichoptera occurring in two sites of the Upper Rhône River (France) we examine: (i) relationships among species traits; (ii) habitat utilization of Trichoptera species; (iii) the relationship between species traits and habitat utilization; (iv) trends of species traits in the framework of spatial–temporal habitat variability to test predictions of the habitat templet concept; and (v) trends of species richness in the framework of spatial–temporal habitat variability to test predictions of the patch dynamics concept.
• 2 Of the sixteen species traits selected, twelve have high correlation ratios for the seventy-five species used in this analysis; these traits are related to behavioural, morphological, or physiological aspects. Traits related to reproduction or life cycle have lower correlation ratios.
• 3 An ordination by species traits separates the five main families into three groups: (i) Hydropsychidae and Polycentropodidae; (ii) Hydroptilidae; and (iii) Leptoceridae and Limnephilidae. An ordination of the habitat utilization of the species in ten habitats indicates that the Hydropsychidae occur preferentially in the main channel, Hydroptilidae, Polycentropodidae, and Limnephilidae occur in backwaters or oxbow lakes, and the Leptoceridae are ubiquitous.
• 4 The Hydropsychidae exhibit a relationship between species traits and habitat utilization, i.e. they use similar habitat types with similar species traits. The species traits of the other four families are similar but their habitat utilization is quite different.
• 5 The Hydropsychidae occur in lowest spatial–temporal variability habitats and Limnephilidae in the highest. Therefore, net spinners and filterers are characteristic of habitats with a low spatial–temporal variability, whereas shredders and case makers using plant material are characteristic of habitats with high spatial–temporal variability. The trends in species traits show little agreement with trends predicted from the river habitat templet.
• 6 Trends of species richness in the framework of spatial and temporal variability do not follow the predictions of the patch dynamics concept because richness is similar in all superficial habitats. This implies that each habitat, in spite of large differences in their spatial and temporal variability, offers Trichoptera a similar but limited number of ecological niches.

     

Traits of benthic macroinvertebrates in semi-natural French streams: an initial application to biomonitoring in Europe

• 1 The methods used to indicate the biological state of streams are often based on taxonomic composition, and the abundance of species or other taxa. This ‘taxonomic structure’ varies among ecoregions and cannot be applied to wider geographical areas. Therefore, we assessed the species traits of benthic macroinvertebrates from semi‐natural reference sites as a potential benchmark for large‐scale biomonitoring. Our purpose was to assess the stability of community structure, based on the representation of taxa and of traits, across large gradients of geology (sedimentary to granitic), altitude (65–1982 m), geographical coordinates (0° 48′ W to 7° 20′ E and 42° 52′ to 48° 44′ N), stream order (1–5) and slope (0.5–60‰).
• 2 We used invertebrate abundance data from the 62 most natural French stream sites available. These abundance data served to weight the occurrence of ‘biological’ traits, such as reproductive characteristics, mobility, resistance forms, food, feeding habits, respiration, and ‘ecological’ traits, such as preferences for temperature, trophic level, saprobity, biogeographic distribution, longitudinal zonation, substratum and current velocity.
• 3 Multivariate analyses of taxonomic composition demonstrated a clear site gradient from lowlands to uplands and from calcareous to granitic geology. In contrast, community structure based on both biological and ecological traits was stable across environmental gradients.
• 4 The frequency distribution of biological traits indicated that the stream benthos of the ‘reference sites’ had a mixture of categories which confirmed theoretical predictions for temporally stable and spatially variable habitats. A mixture of ecological trait categories also occurred at our reference sites. Thus, semi‐natural benthic macroinvertebrate communities are functionally diverse. Moreover, we included an initial application of these traits to a case of slightly to moderately polluted sites to show that the impact of humans significantly changes this natural functional diversity.
• 5 Future studies should focus on the potential for various biological and ecological traits to discriminate different human impacts on the benthic macroinvertebrates of running waters, and on the integration of this functional application into a general ‘reference‐condition’ approach.

     

Invasive willows drive instream community structure

相似文献   

Beavers alter stream macroinvertebrate communities in north-eastern Utah

1. Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver-induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter-mountain west, an area with high potential for beaver-assisted restoration.
2. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in north-eastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver-occupied streams.
3. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches.
4. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers. Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic-dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats.
5. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north-eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.

     

Salamander diversity alters stream macroinvertebrate community structure

相似文献   

Diet composition of two larval headwater stream salamanders and spatial distribution of prey

相似文献   

Functional traits but not environmental gradients explain seed weight in Mongolian plant species

• Seed weight varies by several orders of magnitude among vascular plant species. However, the importance of potential drivers such as environmental conditions and plant functional traits have rarely been assessed for a larger taxonomic sample.
• We collected seeds of 148 species from 237 sites spread across Mongolia and compared their weight among the major zonal vegetation types, taxonomic groups and a set of functional traits (growth form, dispersal mode, fruit type, storage organs and palatability).
• Seed weight strongly varied among all functional traits and taxonomic groups, but no differences among vegetation zones were detected.
• These results suggest a low impact of environmental conditions on the evolution of seed weight, contrasting the strong phylogenetic signal.

     

Theoretical habitat templets, species traits, and species richness: a synthesis of long-term ecological research on the Upper Rhône River in the context of concurrently developed ecological theory

• 1 Based on information obtained from analysis of thirteen taxonomic groups of plants and animals occurring in the alluvial floodplain habitats of the Upper Rhône River, France, we synthesize results obtained on: (i) relationships among species traits; (ii) habitat utilization by species; (iii) the relationship between species traits and habitat utilization; (iv) trends in species traits in a framework of spatial and temporal variability; and (v) tests of trends predicted for species traits and species richness in the framework of spatial and temporal habitat variability in terms of the river habitat templet and patch dynamics concept.
• 2 Species traits describing reproductive characteristics, food, and size had the closest relationships with each other in the various correspondence analyses performed. Faunal and floral separation by species traits produced groupings similar to those based on traditional taxonomy.
• 3 Two major gradients appear in the utilization of the floodplain habitats: a vertical gradient from interstitial to superficial habitats; and a transverse gradient from the main channel to oxbow lakes, temporary waters, and terrestrialized habitats.
• 4 For the majority of the groups examined, a statistically significant relationship was evident between the structure of the species trait and habitat utilization arrays. For these groups, the characteristics of the habitat act as a templet for species traits. Moreover, species trait modalities (i.e. categories defining traits) were significantly arranged along the axis of spatial and temporal variability for most groups, which indicates that such variability acts as a templet for species traits.
• 5 Species traits did not conform to predictions of the river habitat templet because the observed modality sequences did not follow the trends predicted in a framework of spatial and temporal variability. Moreover, there was no clear pattern in the distribution of species traits along an axis of temporal variability for groups of organisms having different sizes, which is a correlate of longevity, nor did modalities of species traits that occur under conditions of low temporal variability also tend to occur under conditions of high spatial variability (or vice versa). Clearly, species traits occur as alternative suites of characteristics in various groups of organisms.
• 6 The patch dynamics concept, which predicts that highest species richness occurs at intermediate levels of temporal variability and highest levels of spatial variability, was supported by observations in only two of the thirteen groups exaniined, and only partially (for spatial variability) when all 548 taxa were examined together.
• 7 The predictions of the river habitat templet and patch dynamics concepts were not supported, perhaps because templet theories do not yet accommodate alternative suites of characteristics and trade-offs between combinations of traits, or perhaps because the single scale of variability considered in the analyses, the inhomogeneity of the available biological information, and the aggregation of spedes traits that were used created methodological problems.
• 8 Ecologically sound river management polides eventually may be based on two key points that emerged from this synthesis: that the habitat acts as a templet for spedes traits, and that composite taxonomic groupings represent relatively homogeneous assemblages of spedes trait modalities.
• 9 The use of statistical approaches developed in this project to analyse other long-term data sets may clarify questions about the applicability of habitat templet theories to river ecology, and hasten development of ecologically sound river management policies.

     

Classification of Reynolds phytoplankton functional groups using individual traits and machine learning techniques

相似文献   

Redundancy and niche differentiation among the European invasive <Emphasis Type="Italic">Elodea</Emphasis> species

Community ecologists implicitly assume redundancy when they aggregate species into functional groups. But there have been remarkably few empirical efforts to investigate the accuracy of this concept in situ. The concept of redundancy could be roughly split into two components: the ecological redundancy (similar response to environmental variations involving similar ecological processes) and the functional redundancy (similar biological trait combinations shaping similar functional processes). Both types of redundancy are tested among the 3 invasive European Elodeas. In 11 sites and during two successive years 2004–2005, the cover growth rate of each Elodea species was monthly recorded. To test ecological redundancy, cover growth rates were related to a large suite of environmental variables. To test functional redundancy, 13 biological traits involved in competitive relationships were measured each month. Firstly, the redundancy hypothesis looks problematic for Elodea ernstiae. Indeed, the later possess numerous biological traits involved in light competition and niche overlap with the other Elodeas is very low. Secondly, ecological and functional redundancy can be successfully applied to Elodea canadensis and Elodea nuttallii. They share a large suite of biological traits leading to wide niche overlaps through the growing season. And the measured environmental variables do not differentially influence their growth rates, which are, in turn, controlled by a similar group of biological traits. In this way, the different invasiveness patterns of E. canadensis and E. nuttallii could be solely due to the ecological drift and their ecological dynamic could follow neutral rules.     

A macroecological perspective of trait patterns in stream communities

相似文献