Year Established: 2019 Start Date: 2019-06-01 End Date: 2020-05-31
Total Federal Funds: $14,953 Total Non-Federal Funds: $36,637
Principal Investigators: H. Arthur Woods
Abstract: Aquatic insects depend on three physical characteristics of streams: flow rates, temperature, and oxygen levels. For mountain-dwelling species in Montana, this typically means fast flows, cold temperatures, and high levels of O2. Climate change is anticipated to drive changes in the abiotic characteristics of mountain streams 1,2. Most importantly, warmer water will depress levels of dissolved O2 and raise the demand for O2 by aquatic species 1,3. Understanding how these physical changes will affect aquatic insects in Montana will require broad, integrative approaches 4,5. Our studies will be carried out using two locally abundant and critically important species, the giant salmonfly (Pteronarcys californica) and the least salmonfly (Pteronarcella badia). Basic research questions: Populations challenged by climate change may show one or more of three broad responses (besides going extinct) 6,7. (1) They can evolve new physiologies or behaviors. (2) They can shift their ranges, often requiring upstream movement to cooler temperatures. (3) They can exhibit physiological or behavioral plasticity that allows them to mitigate challenges and exploit new opportunities. We propose to examine plasticity in respiratory phenotypes of stonefly nymphs in response to different combinations of O2, temperature, and flow. If stoneflies show adaptive plasticity, then we predict dampened range shifts during near-term climate change; if stoneflies do not show adaptive plasticity, then we predict larger shifts and, potentially, local extinction. Our studies will examine plasticity in three respiratory phenotypes: The number and morphology of tracheal gills. The gills, which occur in many species, are thin-walled extensions of the body wall that contain many small tracheal tubes 9. Tracheal gills are key sites of gas exchange. The upper critical temperature of individuals. As temperatures rise, individuals become increasingly stressed directly by high heat and indirectly by inadequate O2 8. Plasticity in gills may affect sensitivity of individuals to high temperatures. The oxygen sensitivity of metabolic rate. As O2 levels fluctuate, individuals with better-developed gills will have metabolic rates that are more robust to hypoxia. Plasticity in all of these traits likely reflects the variability in O2, temperature, and flow that populations experience locally 5,10. Economic significance: Salmonflies are keystone species in aquatic ecosystems. Their activitiesâ€” shredding leaves, recycling nutrients, and altering the physical aspects of stream sedimentsâ€”are critical to overall stream health. Moreover, their importance to trout fisheries is difficult to overstate. They make up a significant proportion of trout diets in many locations. The annual giant salmonfly hatch attracts anglers to the state from all over the globe, and fishing collectively provides more than $900 million in economic activity in Montana every year. Collaboration and training: The proposed measurements leverage the complementary expertise of PIs Malison and Woods. Malison has devised a system to carry out high-throughput metabolic phenotyping of stonefly nymphs, and she is an expert in the ecology and taxonomy of MT stoneflies. Woods has extensive experience working on insect respiratory physiology and morphology and on physiological plasticity, all in the context of climate change. These studies will provide training to one graduate student and several undergraduates.