Collaborative Research: RAPID: The effect of extreme flooding on population genetic structure of freshwater fishes in the southern Appalachians

This project will assess the effect of floods and landslides caused by Hurricane Helene on spatial genetic and phenotypic variation of freshwater fish populations in the southern Appalachian Mountains. Extreme events provide a rare opportunity to investigate the role of disturbance on evolutionary processes. The record-breaking river flows and the transport and deposition of sediment associated with Hurricane Helene is likely to have profound impacts on freshwater fish. Flooding may influence population diversity by causing mortality, physically moving individual organisms across the landscape, or restructuring suitable habitat and dispersal pathways. The project will resample approximately 20 sites across the upper Tennessee River, the Savannah River, and the Santee River in western North Carolina and Tennessee that were previously sampled from 2021-2024, prior to Hurricane Helene. This research will contribute to the essential effort to understand how biodiversity will be affected by a changing planet. The research is of particular importance in the southern Appalachian Mountains, which is located within a temperate freshwater biodiversity hotspot and hosts an exceptional number of freshwater fish species. Results from the proposed work will be communicated to conservation practitioners at the annual Southeastern Fishes Council meeting. Evolution may be contingent on stochastic and impactful events like mutations or extreme abiotic disturbance, and it has been proposed that historical contingency can reduce the degree to which evolution is predictable. Alternatively, natural selection may determine the outcomes of stochastic events, yielding predictable evolutionary trajectories. We will rely on our pre-storm collections of genomic datasets or tissues, targeting seven species that vary in body size, reproductive strategies, and microhabitat preference: Nothonotus chlorobranchius (Greenfin Darter), Etheostoma blenniodes (Greenside Darter), Hypentelium nigricans (Northern Hogsucker), Luxilus coccogenis (Warpaint Shiner), Nocomis leptocephalus (Bluehead Chub), Notropis rubricoceus (Saffron Shiner), and Notropis spectrunculus (Mirror Shiner). The project will use doubledigest restriction site associated DNA sequencing to assess changes in spatial genetic variation before and after the storm, and compare morphological and meristic traits in pre- and post-storm specimens. The project will assess whether the effect on evolutionary processes can be predicted by the degree of abiotic disturbance by using geomorphic observations to estimate discharge and shear stress at maximum flood stage and will assess the influence of landslides and debris flows through analysis of remotely sensed topographic and satellite datasets. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.