Habitat filtering determines spatial variation of macroinvertebrate community traits in northern headwater streams

Abstract

Although our knowledge of the spatial distribution of stream organisms has been increasing rapidly in the last decades, there is still little consensus about traitbased variability of macroinvertebrate communities within and between catchments in near-pristine systems. Our aim was to examine the taxonomic and trait based stability vs. variability of stream macroinvertebrates in three high-latitude catchments in Finland. The collected taxa were assigned to unique trait combinations (UTCs) using biological traits. We found that only a single or a highly limited number of taxa formed a single UTC, suggesting a low degree of redundancy. Our analyses revealed significant differences in the environmental conditions of the streams among the three catchments. Linear models, rarefaction curves and beta-diversity measures showed that the catchments differed in both alpha and beta diversity. Taxon-and trait-based multivariate analyses also indicated that the three catchments were significantly different in terms of macroinvertebrate communities. All these findings suggest that habitat filtering, i.e., environmental differences among catchments, determines the variability of macroinvertebrate communities, thereby contributing to the significant biological differences among the catchments. The main implications of our study is that the sensitivity of trait-based analyses to natural environmental variation should be carefully incorporated in the assessment of environmental degradation, and that further studies are needed for a deeper understanding of trait-based community patterns across near-pristine streams.

Functional diversity: a review of methodology and current knowledge in freshwater macroinvertebrate research

“…Consequently, the unit of this diversity measure is the pattern (combination) of trait states. This concept was used under the name ''unique trait combinations'' in Schmera et al (2012) and Schmera et al (2013). In agreement with the original proposal (Poff et al, 2006) and following the recommendation of Schmera et al (2015), this measure should be called ''number of unique combinations of trait states''.…”

Deconstructing occupancy frequency distributions in stream insects: effects of body size and niche characteristics in different geographical regions

“…The stream surveys in the three basins were conducted in 2008, 2009, and 2010, respectively. The present dataset is largely the same used previously for testing metacommunity patterns (Grönroos et al, 2013), trait structure (Schmera et al, 2013) and occupancy-abundance relationships in stream invertebrates (Heino & Grönroos, 2014). The details of the study areas are reiterated here to facilitate understanding the ecological and geographical settings of the three drainage basins.…”

“…The Tenojoki study area belongs to a subarctic climatic zone, and it is characterised by arctic-alpine vegetation, comprising mountain birch woodlands at a low altitude and barren tundra at a higher altitude. Stream waters are circumneutral (pH ranges from 6.3 to 6.7), and nutrient levels indicate highly oligotrophic systems with total phosphorus values typically below detection limits (Heino, 2013;Schmera et al, 2013). A total of 20 streams were sampled in the Tenojoki drainage basin.…”

“…Each wadeable stream site (i.e. stream width <25 m; stream depth <50 cm; average current velocity <1 m s −1 ) was sampled once in each drainage basin (Heino, 2013;Schmera et al, 2013). Larger river sites were not sampled because high current velocity and deep waters precluded taking representative samples.…”

Spatio-temporal variability of benthic macrofauna in a coastal lagoon assessed by ecological interaction networks

“…Environmental differences in space and time are usually responsible for differences in the diversity and composition of macroinvertebrate communities. Consequently, natural environmental differences generate variation in the functional diversity and community patterns of macroinvertebrates (Schmera et al 2013). …”