Collaborative Research: ORCC: The role of bioenergetic budgets in defining elevation limits and modeling geographic ranges of species

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Freshwaters cover only 0.8% of Earth’s surface, yet these ecosystems harbor 31% of global fish biodiversity. Ongoing climate change is altering the physiology and behavior of fishes, and subsequently allowing some species to expand their geographic ranges while driving range retraction of other species. The goal of this project is to forecast how changing climate is shifting the lower and upper elevation limits of fishes in mountain streams and rivers. The research will take place along an elevational stream continuum in the southern Appalachian Mountains—a hotspot of biodiversity harboring unique fishes that are essential for maintaining healthy freshwater ecosystems on which humanity depends. The research team will perform laboratory experiments to measure the effect of temperature on fish physiology, behavior, and growth. New computational techniques will be used to integrate data from these laboratory experiments with a 2-year field study of wild fish populations to create detailed maps of elevational shifts during the remainder of the 21st century. Throughout the project, the research team will host workshops with conservation practitioners to transform research findings into real-world tools that can immediately inform conservation decisions. A professional development workshop will be hosted for K-12 teachers in Knoxville, TN, and laboratory experiments will take place at a Hispanic Serving Institution in San Antonio, TX, thus advancing societal goals of diversity, equity, and inclusion in STEM education.This project will develop the next generation of species distribution models (SDMs) by integrating organism-level bioenergetic budgets with community-level predator-prey interactions. The goal is to improve understanding of how physiological and behavioral traits as well as multiple, simultaneous environmental factors associated with climate and land use change drive geographic range limits. The following hypotheses will be tested: (1) Elevational limits of species are concordant with transitions from energy surplus to deficit along the elevation gradient. (2) Physiological and behavioral traits of species determine the relative effects of temperature, stream flow, and prey abundance on elevational differences in organismal energy budgets. This next-gen SDM framework will be validated using a species comparative approach, focusing on low- and high-elevation pairs of pelagic (water column) minnows and benthic (stream bottom) darters. Once validated, SDMs will be projected under future scenarios of temperature, stream flow, and prey abundance to forecast shifts in species elevational and latitudinal limits. Because the inputs for these next-gen SDMs are thermal reaction norms, eco-evolutionary hypotheses based in established theory of thermal adaptation (e.g., countergradient variation) will be used to explore how thermal niche evolution might attenuate future shifts in species range limits. More generally, project findings will advance understanding of species range limits by explicitly integrating Grinnellian and Eltonian niche concepts to elucidate underlying mechanisms.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.