Morphological Variation in Campostoma Anomalum Across Hydrologic Regmies

Environmental heterogeneity in streams is largely determined by hydrologic regimes. Because hydrology controls many attributes of the physical environment, organisms adapt and evolve in response to maintained hydrologic regimes. Adaptations may be the result of phenotypic plasticity or genetic divergence, both of which play roles in speciation and evolution. This research utilizes a comparative field study and mesocosm experiment to determine (1) morphological differences between Campostoma anomalum inhabiting two distinct flow regimes and (2) whether phenotypic plasticity or genetic divergence is predominantly driving morphological variation in Campostoma anomalum across hydrologic gradients. We hypothesize Campostoma anomalum from hydrologically variable streams will exhibit smaller anterior body regions, larger caudal regions and less streamlined forms, while Campostoma anomalum from hydrologically stable streams will exhibit larger anterior body regions, smaller caudal regions and streamlined bodies, and variation in body morphology is predominately due to genetic divergence between populations. This study contributes to the understanding of how environmental factors drive natural selection, and may provide insight into the evolutionary consequences of disrupting natural hydrologic patterns, which are increasingly threatened by climate change and anthropogenic alterations.