1. Fish and invertebrate assemblage data collected from 670 stream sites in Minnesota (U.S.A.)
were used to calculate concordance across three nested spatial scales (statewide, ecoregion and
catchment). Predictive taxa richness models, calibrated using the same data, were used to
evaluate whether concordant communities exhibited similar trends in human-induced taxa
loss across all three scales. Finally, we evaluated the strength of the relationship between
selected environmental variables and the composition of both assemblages at all three spatial
2. Significant concordance between fish and invertebrate communities occurred at the
statewide scale as well as in six of seven ecoregions and 17 of the 21 major catchments.
However, concordance was not consistently indicative of significant relationships between rates
of fish and invertebrate taxa loss at those same scales.
3. Fish and invertebrate communities were largely associated with different environmental
variables, although the composition of both communities was strongly correlated with stream
size across all three scales.
4. Predictive taxa-loss models for fish assemblages were less sensitive and precise than models
for invertebrate assemblages, likely because of the relatively low number of common fish taxa in
our data set. Both models, however, distinguished reference from non-reference sites.
5. The importance of concordance, geographic context and scale are discussed in relation to the
design and interpretation of stream integrity indicators. In particular, our findings suggest that
community concordance should not be viewed as a substitute for an evaluation of how
assemblages respond to environmental stressors.
Dolph, Christine, L.; Huff, David, D.; Chizinski, Christopher, J.; Vondracek, Bruce.
Implications of community concordance for assessing stream integrity at three nested spatial scales in Minnesota, USA.
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