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description:
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This data was created as part of the Missouri Aquatic Gap Project. Ecological Drainage Units (EDUs) are largely zoogeographic substrata of Subregions. EDUs were empirically derived and represent fairly large watersheds or subdrainages (approx 2,500-10,000 mi²) containing aquatic assemblages that are relatively distinct within the context of the surrounding Subregion. Our EDUs are quite similar to the faunal divisions of Pflieger's Aquatic Community Classification for Missouri (Pflieger 1989). We decided not to simply adopt these faunal divisions for two important reasons. First, Pflieger utilized 1,608 community fish samples to generate the constancy/fidelity indices he used to delineate his faunal divisions. We had at our disposal those same 1,608 samples plus nearly 1,000 additional samples. Second, we had assembled 1,000's of collection records for 3 other taxa (crayfish, mussels, and snails) that we believed should be included in any effort to delineate zoogeographic subunits of our three Aquatic Subregions. |