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Aim: Habitat templet theory predicts that the functional niches of species evolved in response to selection pressures imposed by each species' spatial–temporal environment. Consequently, similar environmental conditions should lead to convergence in the biological trait composition of biogeographically independent assemblages. Given their high diversity and ubiquitous occurrence, stream insects represent an ideal group to test convergence. Such an analysis should provide insight into both how spatially variable stream insect traits are and how transferable trait–environment relationships are across large spatial scales. We tested two hypotheses: (1) functional niches of stream insects are similar across Australia, Europe, North America, New Zealand and Southern Africa, and (2) the variability in trait profiles of stream insects is positively related to climatic variability within regions. Location: Australia, Europe, North America, New Zealand and Southern Africa. Methods: We used trait datasets from each region to compare functional niches and to delineate groups of insects with similar trait profiles (hereafter, trait profile groups or TPGs) in each region. We identified the traits most important in separating TPGs. Finally, we assessed if trait profile variability between TPGs was associated with climatic variability within each region. Results: We found that functional niches of families largely overlapped across the regions examined, except for partial deviations of some Australian families, but that only two trait combinations characterized TPGs across all regions. Feeding mode and respiration traits consistently drove the separation of families into TPGs. The variability of trait profiles slightly increased with increasing climatic variability. Main Conclusions: Although our study did not allow to demonstrate mechanisms, it is the first to show large similarities between stream insect functional niches across different biogeographic regions, which might be an indication of their convergence. An important factor shaping stream insect assemblages over these large scales might be climate, indicated by the higher trait profile variation in regions with more diverse climates. [ABSTRACT FROM AUTHOR]

Freshwaters are impacted by many pollutants. Scientists and resource managers need to reliably detect and monitor these pollutants by employing appropriate sampling techniques to quantify and mitigate their impacts. Emerging freshwater contaminants such as microplastics are difficult to monitor as effective sampling techniques have not been fully developed and lack standardization. Here, we propose a novel method, adapted from stream invertebrate kick‐net sampling, which can be employed for long‐term, standardized microplastic monitoring. We hypothesized that invertebrate kick‐net sampling would be effective at collecting microplastics, capturing higher microplastic concentrations than standard microplastic sampling, due to collecting suspended and benthic microplastics simultaneously. We sampled 28 streams for microplastics using standard drift and sediment microplastic collection methods and invertebrate kick‐netting. As predicted, kick‐netting captured microplastics at higher concentrations than conventional sampling, regardless of whether values were expressed per volume of water (as in drift samples), per kg of sediment or per area sampled (as in benthic samples). Consequently, kick‐net sampling has the potential to be a time‐ and cost‐efficient tool for monitoring microplastic pollution. We recommend the employment of invertebrate kick‐netting as a new, standardized means to investigate and routinely monitor microplastic concentrations worldwide. This would generate a more robust dataset of global freshwater microplastic pollution, making it possible to answer unresolved questions pertaining to changes in microplastic pollution profiles. Standardized, long‐term records of microplastic concentrations in freshwaters would also allow a more accurate assessment of the ecological risks of microplastic pollution. Finally, long‐term microplastic data could be used to inform much‐needed regulatory decisions pertaining to microplastic pollution. [ABSTRACT FROM AUTHOR]

Excessive fine sediment (particles <2 mm) deposition in freshwater systems is a pervasive stressor worldwide. However, understanding of ecological response to excess fine sediment in river systems at the global scale is limited. Here, we aim to address whether there is a consistent response to increasing levels of deposited fine sediment by freshwater invertebrates across multiple geographic regions (Australia, Brazil, New Zealand and the UK). Results indicate ecological responses are not globally consistent and are instead dependent on both the region and the facet of invertebrate diversity considered, that is, taxonomic or functional trait structure. Invertebrate communities of Australia were most sensitive to deposited fine sediment, with the greatest rate of change in communities occurring when fine sediment cover was low (below 25% of the reach). Communities in the UK displayed a greater tolerance with most compositional change occurring between 30% and 60% cover. In both New Zealand and Brazil, which included the most heavily sedimented sampled streams, the communities were more tolerant or demonstrated ambiguous responses, likely due to historic environmental filtering of invertebrate communities. We conclude that ecological responses to fine sediment are not generalisable globally and are dependent on landscape filters with regional context and historic land management playing important roles. [ABSTRACT FROM AUTHOR]