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THE EFFECTS OF MACROINVERTEBRATE TAXONOMIC RESOLUTION IN LARGE LANDSCAPE BIOASSESSMENTS: AN EXAMPLE FROM THE MID-ATLANTIC HIGHLANDS, USA
Citation:
Waite, I. R., A. T. Herlihy, D P. Larsen, N. S. Urquhart, AND D J. Klemm. THE EFFECTS OF MACROINVERTEBRATE TAXONOMIC RESOLUTION IN LARGE LANDSCAPE BIOASSESSMENTS: AN EXAMPLE FROM THE MID-ATLANTIC HIGHLANDS, USA. FRESHWATER BIOLOGY 49:474-489, (2004).
Description:
The macroinvertebrate taxonomic resolution needed for detecting human impacts on stream ecosystems draws continued attention from stream ecologists. During late spring 1993-1995, the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) sampled 490 wadeable streams in the mid-Atlantic Highlands (MAH) of the U.S. for a variety of physical, chemical, and biological indicators of environmental condition. We used the resulting data set to evaluate the taxonomic resolution question by comparing the ability of family vs. genus to detect differences among sites classified by type and magnitude of human impact and by stream size. We divided the MAH into two regions: the Plateau, affected by mine drainage (MD) and atmospheric deposition, and the Ridge and Valley, affected by nutrient enrichment. We used stream order (1st ? 3rd Strahler order) in each region as a measure of stream size. Ordination, 2x2 Chi-square, discriminant function analyses (DFA), and richness metrics were used to compare the ability of family and genus to detect differences among predefined classes. Family and genus data were similar in their ability to distinguish among the coarse impacts (e.g., most severe vs. least severe impact classes) for all cases. Though genus data in general distinguished the subtler differences (e.g., mixed/moderate impacts vs. high or low impacts) better than family, the improvement between the taxa levels was relatively minor. However, genus data detected differences among stream orders in both the DFA and ordination analyses that were not revealed at the family level. Both family and genus responded to approximately the same suite of environmental variables (ordination results). In general, we found 3-4 genera or fewer per family, with one notable exception: 123 genera within the family Chironomidae. As a result, significant information loss occurred when this group was only classified to family. The family Chironomidae did not discriminate among the predefined classes but many chironomid genera did: 10 and 28 chironomid genera were significant in the Chi-square analyses for the MD and nutrient impacts, respectively and between 37 - 50% of the significant taxa selected in the various DFA models were chironomid genera. Our results suggest that identification to the family level may be sufficient for many circumstances if a family is composed of few genera, but if a family consists of many genera, the finer taxonomy would provide significantly improved resolution.