Derivation of Hydrogeomorphic Variables for Fundamental Niche Modeling of Unionid Mussel Concentrations in Missouri Ozark Rivers

The Meramec River basin, located in the northeastern Ozark region of Missouri, has one the most diverse mussel faunas in the Midwest. Basin-wide mussel surveys documented declines in species richness and diversity in this system over the past thirty years. However, the mechanisms leading to this decline are poorly understood. A better understanding of the habitat requirements of mussels will provide insight into the causes of mussel decline, which will improve conservation management actions. In this project, we use remotely sensed datasets to identify the basic physical habitat requirements related to channel hydraulics, hydrology, and geomorphology that are needed to support diverse aggregations of mussels. The maximum entropy modeling method (Maxent) was applied to generate a fundamental niche model based on the hydrogeomorphic input variables and known locations of diverse mussel assemblages. This method uses incomplete information (i.e., presence only data) to find the probability of distribution of maximum entropy (i.e., closest to uniform) given the constraints of known locations and environmental variables. The model identifies locations throughout the Meramec Basin that provide the fundamental characteristics allowing establishment of diverse mussel aggregations. Model predictions and identification of additional limiting factors for mussels through field surveys will begin summer of 2016