Changes in Assemblage Structure and Species Interactions Accompanying Rapid Warming in the Upper Mississippi River

In rivers, the rate of warming and the topography of the landscape are primarily responsible for governing climate velocity, or the rate at which climates shift across landscapes. In the Upper Mississippi River System, rapid warming and low gradients combined to produce high climate velocities in the past quarter century. Species turnover accompanying the high climate velocities was relatively low, which is probably a result of high initial overlap in species distributions. Instead, shifts in the assemblage structure, co-occurrence patterns, and size structure indicate substantial changes have emerged. The results from the Upper Mississippi River System suggest its fish assemblage is responding differently from that of rivers with smaller sizes and higher gradients, and these patterns may be characteristic of climate change responses in other large rivers.