Streamflow regimes and geologic conditions are more important than water temperature when projecting future crayfish distributions

Ongoing changes in climate are expected to alter current species' habitat and potentially result in shifts in species distributions. While climatic conditions are important to a species' ability to persist in an area, for many taxa, other environmental factors, such as geology, land cover, and topography, are also important for providing suitable habitat. Furthermore, aquatic species experience changes in climatic conditions through the effect precipitation and air temperature have on streamflow regimes and water temperature. In this study, species distribution models (SDMs) for ten stream-dwelling crayfish species were generated using a maximum entropy approach across the Mobile River Basin in the southeastern United States. SDMs were developed using model-generated contemporary estimates of streamflow and water temperature as well as geologic, topographic, and land cover data. Future distributions were then projected using global climate model (GCM) projections of streamflow and water temperature. Geology, topography, and streamflow appear to be more important predictors of suitable habitat than water temperature for crayfish species within the Mobile River Basin. Species distributions regulated by limited influences from stream flow and water temperature displayed relatively small changes in projected future habitat distributions based on various GCM scenarios. When shifts in species distributions were projected into the future, these shifts did not appear to follow a northward retreat or expansion, likely due to the limited impact of water temperature on the modeled distributions of suitable habitat for these species. Furthermore, species' habitat distribution responses among future climate scenarios were variable within and among species and did not vary unidirectionally with increased severity of climate change as realized through increased warming patterns.