Niche partitioning of food resources by freshwater mussels in a multispecies mussel bed in the Sabine River, Texas

Freshwater mussels are filter feeders that play an integral role in keeping our water systems healthy. Filter feeding influences the entire ecosystem through the transfer of energy, cycling of nutrients, and purification of water. Freshwater mussels form multispecies assemblages which may lead to food resource competition among species. This study focuses on determining which suspended food resources freshwater mussels consume and evaluates if, and to what extent, mussels in a multispecies bed are partitioning available food resources. We examined the available food resources consumed by four species of freshwater mussels, Bleufer (Potamilus purpuratus), Pistolgrip (Tritogonia verrucose), Texas Pigtoe (Fusconaia askewi), and Yellow Sandshell (Lampsilis teres), from a single mussel bed in the upper Sabine River of East Texas. Using eDNA as a measure of food availability, we found that bacteria were consumed at a higher richness and diversity than phytoplankton or zooplankton. Furthermore, we found low niche overlap of bacteria between mussel species suggesting niche partitioning may be common for freshwater mussels despite being found in a flowing river environment with potentially unlimited resources. We also found that the richness and diversity of bacteria consumed by the Yellow Sandshell is statistically higher than Pistolgrip and that these species have moderate niche overlap (0.556). These data and previous habitat data indicate that the Pistolgrip can be classified as an ecological specialist species and the Yellow Sandshell as an ecological generalist species. Overall, these results support ecological theory that mussels co-exist in the same environment because they utilize different resources.