Taxonomy and stream ecology—The benefits of genus- and species-level identifications

Why do people name things? Would we get the same information content if we refer to a particular structure as a black oak tree, an oak tree, a tree, a plant, a living object, or just as a thing? Regular observers at sporting events know the truth behind the aphorism ‘‘you can’t tell the players without a scorecard’’. The value of naming an organism is that after we name it, we can assign characteristics to it and know those characteristics the next time or place we see it. It also allows us to refine its categorization by comparing and contrasting it to similar organisms. The value of a name is also readily apparent when we look at aquatic organisms. We may encounter thousands of different organisms, from microscopic bacteria to fish, if we study just a single stream. Some groups of stream organisms are well-known and generally easy to name (e.g., fish), others require some training (e.g., invertebrates and algae), and some groups can be named only by a few specialists (e.g., bacteria). Naming even all the well-known groups in a single stream segment, such as identifying all the aquatic insects, can be a daunting task. Merritt et al. (1984) estimated that 100 to 250 insect species typically occupy headwater streams (orders 1–3) and 200 to 500 insect species occupy midreach rivers (orders 4–6). High numbers of macroinvertebrate taxa at single stream sites also have been found in North Carolina, where repeated summer collections (n 5