How is reproductive timing regulated in freshwater mussels?
Freshwater mussels (Unionidae) are some of the most highly threatened animals in the United States and around the world. Understanding why these organisms are so sensitive is critical to preventing further species declines. Therefore, I am interested in the factors that regulate the timing of freshwater mussel reproduction, the most sensitive period of most animals' lives. Specifically, I am examining how temperature, photoperiod and food availability interact to influence mussel physiology (energy reserves) and reproductive output. (Photo: collecting gonad samples using a non-lethal syringe biopsy technique)
How does reproductive timing influence fertilization success in freshwater mussels?
Many streams in Oklahoma are highly variable in both temperature and flow. During hot summer months, streams become intermittent (dry in areas), turning long stretches of river into a series of isolated pools. River regulation further exacerbates these harsh conditions. Part of my research focuses on how mussel fertilization success is influenced by these harsh conditions, particularly low flow and high temperatures. I am interested in sperm viability in relation to water temperature and how this might interact with reproductive timing to influence fertilization success. I am also interested in how streamflow corresponds to timing of reproduction and how this might influence gene flow (i.e. downstream movement of sperm) among mussel beds. (Photo: filter feeding Actinonaias ligamentina in the Glover River)
What are the mechanisms of reproductive isolation in closely related mussel species?
Because mussels are broadcast spawners and have high rates of dispersal and gene flow, speciation in these organisms has been assumed to be rare. However, freshwater mussel beds often contain numerous closely related species, indicating that speciation might not be as rare as once thought. Understanding the process of speciation in freshwater mussels requires a more thorough knowledge of the mechanisms of reproductive isolation. Therefore, I am interested in the barriers to interspecific fertilization in three closely related species of mussels (Quadrula cylindriva, Q. pustulosa, Q. quadrula). My research focuses on habitat use, timing of reproduction, sperm chemotaxis, and gamete incompatability as mechanisms for "ensuring" conspecific fertilization. (Photo: collecting mussels with Tulah in the Little River)