Early Registration Deadline
12 February 2010

Travel Award & Grant Recipients Notified
March 2010

Authors Notified
April 2010

Schedule Posted
January 2010

Snyder, C. D., U.S. Geological Survey, Kearneysville, USA, csnyder@usgs.gov
Hitt, N. P., U.S. Geological Survey, Kearneysville, USA, nhitt@usgs.gov
Smith, D. R., U.S. Geological Survey, Kearneysville, USA, drsmith@usgs.gov
Daily, J. P., U.S. Geological Survey, Kearneysville, USA, jdaily@usgs.gov

USING SIMULATIONS TO EVALUATE THE EFFECT OF TAXONOMIC RESOLUTION ON THE SENSITIVITY OF MACROINVERTEBRATE BASED STREAM CONDITION MEASURES

Benthic macroinvertebrates are widely used to assess stream condition but the appropriate taxonomic resolution for analysis remains controversial. On one hand, analysis of genera and species (i.e., lowest practical resolution) would be expected to quantify highly-tolerant and highly-intolerant taxa thereby increasing sensitivity to stressors. On the other hand, analysis of family-level data may reduce the variability of reference communities thereby increasing the probability of detecting non-reference conditions. In this study, we simulated degradation of macroinvertebrate reference communities in the Shenandoah National Park and evaluated the sensitivity of two bioassessment indices (Macroinvertebrate Biological Integrity Index and Bray-Curtis Similarity Index) calculated at the family level and lowest practical level. We based the simulations on data from two sites that naturally varied in terms of taxon diversity. Simulation results indicated little or no gain in sensitivity by identifying specimens to the lowest practical taxonomic level. Results were robust to the effects of taxon richness suggesting their general applicability. Based on these findings, we recommend identifying specimens to the family level and using the cost savings to increase sampling effort.

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