Reconstructing the Historic Distributions of Mussel Species in Wadeable Streams of Illinois

Freshwater mussels are the most imperiled aquatic species in United States. One of the challenges in effectively protecting and restoring mussel biodiversity is lack of understanding of their historic distributions at a relevant spatial scale. Without this information, it is difficult to assess the current state of individual species and overall biodiversity, and to evaluate restoration success. In the present study, we compiled records for 45 mussel species in Illinois wadeable streams and a range of natural environmental variables describing climate, geology, soil, land-covers, and watershed topography. We used reaches (segments between two neighboring tributaries) as the basic spatial unit of stram network for Maxent modeling. We applied the models to all identified wadeable reaches. Stalking the predictions of individual mldels yielded an estimate of species richness for  each reach. The estimates were validated based on 18 sites that were thoughly sampled in the early time. We further assessed the loss of mussel species at the reach scale and the proportional loss of the predicted range of individual species using a subset of sites sampled intensively in recent years. We discussed the spatial patterns of historical diversity and implications of our modeling for mussel-based assessment of stream health.