Environmental Protection Using DNA Barcodes or Taxa?

There is increasing interest among conservation biologists in using DNA barcodes to document biological diversity, and in using the barcode data to replace morphologically based taxonomic data. Taxonomic data, traditionally obtained by observing the morphological and anatomical characteristics of organisms, have been the foundation of conservation biology and ecological assessments for decades, using taxa presence, their associated ecological characteristics, and assemblage-level diversity as biological indicators of ecological health (Angermeier and Karr 1994). In the discipline of ecological monitoring and assessment, my colleagues and I have found a fairly consistent error rate associated with applied taxonomy of 10 to 15 percent (most testing has been done with freshwater benthic macroinvertebrates)—and this is at the level of genus. The number would undoubtedly be much higher for species-level identifications. Some scientists are concerned that similar error may exist with data on other assemblages (specifically, fish and periphyton), but this is as yet untested. I have heard three recommendations from within the monitoring community for dealing with this taxonomic error: (1) Base ecological assessments on DNA barcoding, as it will eliminate all taxonomic error; (2) base ecological assessments on family-level taxonomy, as it will reduce the rate of taxonomic error to acceptable levels; and (3) accept the 10 to 15 percent uncertainty, and move forward with the assessments. The first recommendation, which calls for more detailed data, represents a misunderstanding of what DNA barcoding is, of how those data relate to taxonomic diversity, and of the uncertainties inherent in translating genetic data into taxonomic data. The second, a call for more coarse data,risks losing ecological information available at finer taxonomic levels (genus or species), which is critical to interpreting ecological assessments in a way that integrates the diversity of environmental pressures on ecosystems. The third, to which I adhere, is a compromise between the first two, and also recognizes the uncertainty in all technical endeavors.