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Raunio J.,Water and Environment Association of the River Kymi | Heino J.,Finnish Environment Institute | Paasivirta L.,Ruuhikoskenkatu 17
Ecological Indicators | Year: 2011

Non-biting midges (Diptera: Chironomidae) are frequently overlooked in freshwater biodiversity surveys and environmental assessment, yet they are commonly the most abundant and the most diverse taxon in freshwater ecosystems. We reviewed the diversity patterns and assemblage-environment relationships of non-dipterans and chironomids mainly in boreal freshwater ecosystems building on previously reported findings. Although generally the same environmental gradients are correlated with assemblage structure, their relative importance varies between chironomids and non-dipterans. Chironomid assemblage response to and recovery from human impacts are also likely to differ from that of other common benthic taxa. Thus, environmental assessments may be biased if chironomids are not included. Different surrogacy approaches have thus far shown little success in accounting for chironomid species richness and assemblage structure, and there appears to be no easy short-cut for the examination of chironomids as part of freshwater surveys. However, we show that genus-level identification of pupal exuviae provides a reliable and rapid way of estimating chironomid species richness at least in boreal freshwater ecosystems. In addition, we demonstrate that the inclusion of chironomids may increase the signal-to-noise ratio in bioassessment data sets, and that this information can be obtained with modest increases in costs. © 2010 Elsevier Ltd.


Heino J.,Finnish Environment Institute | Heino J.,University of Oulu | Ilmonen J.,Metsahallitus | Paasivirta L.,Ruuhikoskenkatu 17
Boreal Environment Research | Year: 2014

Our aim was to examine the nature of macroinvertebrate community variation across a set of streams in three drainage basins in Finland. We found that there were no clearly discrete community types, but rather macroinvertebrate communities varied continuously along environmental gradients. Local environmental factors and geographical location were strongly collinear and both were important in accounting for variation in macroinvertebrate community structure in the multivariate regression tree analysis and based on a combination of k-means clustering and discriminant analysis. We conclude (i) that geographical location and local environmental factors are strongly intertwined and both are associated with variation in macroinvertebrate communities across northern streams at the spatial scale of the three drainage basins studied; and (ii) that environmental assessment and conservation studies should not rely too much on delineating "community types", but rather acknowledge the continuous variation of stream macroinvertebrate communities. © 2014.


Heino J.,Finnish Environment Institute | Heino J.,University of Oulu | Gronroos M.,Finnish Environment Institute | Gronroos M.,University of Oulu | And 4 more authors.
Freshwater Science | Year: 2013

Theory predicts that different components of species diversity should increase with environmental heterogeneity. Our main aim was to examine the relationship between β-diversity and environmental heterogeneity in a system with high habitat heterogeneity and very small spatial distances between sites. This system allowed us to examine the effect of habitat heterogeneity on β-diversity in the absence of dispersal limitation. We surveyed 100 riffle sites (10 riffles in each of 10 streams) for benthic macroinvertebrates in a boreal drainage basin. Streams differed in average community composition (based on canonical analysis of principal coordinates) and heterogeneity in community composition (based on test of homogeneity of dispersion). These results were robust regardless of the distance measures used in distance-based multivariate analyses. β-diversity was not significantly correlated with stream habitat heterogeneity, despite the fact that the latter was quantified by a large set of environmental variables deemed important for species occurrence in our study streams. Thus, we suggest that the relationship between β-diversity and habitat heterogeneity was masked by individual species-environment responses and mass effects. Thus, the β-diversity-habitat heterogeneity relationship may not always be significant, a result that may have important consequences for understanding the structure of community patterns. Despite the absence of a significant β-diversity-habitat heterogeneity relationship, community structure was significantly associated with environmental factors (e.g., moss cover, stream width, velocity) across the streams in distance-based redundancy analysis. This finding suggests that different ways to associate β-diversity, community structure, and environmental conditions may yield different insights into the structure of biotic communities. © 2013 by The Society for Freshwater Science.


Karna O.-M.,University of Oulu | Gronroos M.,Finnish Environment Institute | Antikainen H.,University of Oulu | Hjort J.,University of Oulu | And 3 more authors.
Journal of Animal Ecology | Year: 2015

Metacommunity research relies largely on proxies for inferring the effect of dispersal on local community structure. Overland and watercourse distances have been typically used as such proxies. A good proxy for dispersal should, however, take into account more complex landscape features that can affect an organism's movement and dispersal. The cost distance approach does just that, allowing determining the path of least resistance across a landscape. Here, we examined the distance decay of assemblage similarity within a subarctic stream insect metacommunity. We tested whether overland, watercourse and cumulative cost distances performed differently as correlates of dissimilarity in assemblage composition between sites. We also investigated the effect of body size and dispersal mode on metacommunity organization. We found that dissimilarities in assemblage composition correlated more strongly with environmental than physical distances between sites. Overland and watercourse distances showed similar correlations to assemblage dissimilarity between sites, being sometimes significantly correlated with biological variation of entire insect communities. In metacommunities deconstructed by body size or dispersal mode, contrary to our expectation, passive dispersers showed a slightly stronger correlation than active dispersers to environmental differences between sites, although passive dispersers also showed a stronger correlation than active dispersers to physical distances between sites. The strength of correlation between environmental distance and biological dissimilarity also varied slightly among the body size classes. After controlling for environmental differences between sites, cumulative cost distances were slightly better correlates of biological dissimilarities than overland or watercourse distances between sites. However, quantitative differences in correlation coefficients were small between different physical distances. Although environmental differences typically override physical distances as determinants of the composition of stream insect assemblages, correlations between environmental distances and biological dissimilarities are typically rather weak. This undetermined variation may be attributable to dispersal processes, which may be captured using better proxies for the process. We suggest that further modifying the measurement of cost distances may be a fruitful avenue, especially if complemented by more direct natural history information on insect dispersal behaviour and distances travelled by them. © 2015 British Ecological Society.

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