Wednesday, June 6, 2007 - 4:30 PM
330

Ecological variation within and among chironomid subfamilies and tribes: implications for ecological studies and bioassessments

Brian R. Creutzburg and Charles P. Hawkins. Western Center for Monitoring and Assessment of Fresh Water Ecosystems, Department of Watershed Sciences, and Ecology Center, Utah State University, 5210 Old Main Hill, Logan, UT 84322

High-level taxa (e.g., subfamilies) may be useful in ecological studies if taxonomic hierarchies describe ecologically nested subsets of taxa in which distinct ecological signals do not decrease too severely with increasing levels of taxonomy.  High-level taxa are frequently used in freshwater ecological analyses and bioassessments, but the amount of ecological information lost when doing so is generally unknown.  This issue is especially problematic for the chironomids, for which individuals are often identified to subfamily or tribe.  We quantified the niche locations of 99 stream-inhabiting genera with respect to 16 environmental factors and then determined how much ecological information was lost when individuals were identified to subfamily and tribe.  We measured (ANOVA) the amount of ecological variance among genera that was associated with 5 subfamilies and 8 tribes.  On average, subfamily and tribe explained only 13 and 18% of the ecological variation among genera.  Only the tribe Chironomini (subfamily Chironominae) inhabited unique niche space.  Genera in this tribe tended to inhabit warmer streams than genera in the other subfamilies and tribes.  These results imply that we can infer little ecological information from coarse-level chironomid taxonomy, and if coarse taxonomy is used, only two groupings can be justified: Chironomini and everything else.