Abstract: Regional faunal assessments of aquatic insect biodiversity in the Midwestern, USA (herein defined as Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, and Wisconsin) indicate severe losses in agricultural regions resulting from stream channelization, pesticide and fertilizer application, and sedimentation. The greatest losses have been recorded in multivoltine guilds found in large rivers. Using an expansive occurrence dataset of stonefly (Order Plecoptera) records compiled from 25 regional institutions, we present distribution models for 114 of the 153 Midwestern species across two temporal periods: pre-European colonization and the contemporary period. Predictions of Midwestern species richness trends were identified for each temporal period by stacking distribution models. The goals of this study were to identify regions of range contraction, expansion, or persistence for modeled taxa. We present models predicting distribution prior to large-scale land conversion for agricultural purposes, and identify regions with the greatest losses of fauna related to current land use. We identified range contractions across taxa in regions of intensive agricultural practices. Historically unglaciated and higher latitude regions of the study area maintained the greatest proportion of species richness between temporal periods modeled. Correlations between species' life history traits and trends of predicted habitat suitability range expansion and contraction across temporal periods are used to identify species at risk for future extirpation.
