Lumping and Splitting of Distribution Models Across a Biogeographic Divide Informs the Conservation of an Imperiled Fluvial Fish.

Freshwater fishes are among the most threatened taxa in the world. A major challenge for the conservation and management of threatened fishes is scarce information regarding life history, habitat requirements, and the drivers of declines. Species distribution models (SDMs) that leverage existing occurrence records and geospatial data have aided in addressing these challenges. We used SDMs to better understand large-scale distributional patterns of Bluntface Shiner (; BFS), a minnow facing declines across its range. We modeled the potential distribution of BFS based on natural, abiotic factors and existing occurrence records to identify landscape-scale factors underlying their distribution. We also compared environmental conditions between their disjunct ranges east and west of the Mississippi River and examined model transferability when projecting models into opposing ranges. Our analyses revealed a naturally fragmented distribution both east and west of the Mississippi River, but populations to the east of the Mississippi River occupy streams with broadscale environmental conditions that differ from those to the west. Models projected across the Mississippi River did not reflect the contemporary range of BFS, underscoring differences in occupied niches on either side of the biogeographic divide and emphasizing the need for caution when projecting SDMs to novel ranges. Our results provide a baseline to gauge range loss of BFS, highlight areas of high suitability for conservation, and identify locations where further sampling or research may be warranted.