Does insufficient oxygen constrain elevational range shifts? An integrative test in dragonflies

About This Grant

Animals all over the world are being pressured to move to new habitats at higher latitudes and higher elevations. While many species are successfully moving towards the poles, relatively few are migrating upslope as fast as they need to. One intuitive but untested explanation for this mismatch could be that high-elevation habitats do not provide enough oxygen to support lowland species’ essential activities (e.g. foraging, mating, evading predators). As a model organism for testing this hypothesis, the project will use dragonflies, whose extreme aerobic requirements during flight should make them especially sensitive to the low oxygen at high elevations. By combining an integrative set of lab experiments with a large-scale field inventory of dragonfly species in the Rocky Mountains, the research will advance our understanding of the barriers that animals face when dispersing into a new environment. This project will further help scientists and land managers make better forecasts for the kinds of traits that animal species will need in order to establish populations at higher elevations. This work will also provide training opportunities for the next generation of scientists and produce a report about the statuses of dragonfly species on public lands in Colorado. The goal of this project is to test if low oxygen prevents species from dispersing to higher elevations. Using dragonflies as a model, the proposed approach will explore this putative physiological barrier across three aims: (1) Test if low oxygen inhibits locomotor performance of dispersing adults during any elevational range shift or only during shifts into the most extreme elevations. A replicated transplant experiment in the Rocky Mountains and Appalachian Mountains will assess how flight performance is affected when the putative constraint of low oxygen is relaxed at high elevations and imposed at low elevations. (2) Test if the species that are most tolerant of low oxygen have shifted upslope the farthest in the last 20 years. A field survey of the Rocky Mountains will determine how species’ elevational limits have changed in Colorado since the early 2000s, and lab assays will assess if these shifts are related to the species’ physiological characteristics. (3) Test if a species’ ability to engage in aerobically demanding activities is impeded more by lower oxygen or warmer temperature. A respirometry experiment will evaluate how aerobic scope will be affected by the future conditions in species’ current elevations versus the atmospheric conditions at the elevations where they are expected to migrate. Overall, by integrating respirometry, whole-organism performance trials, and biogeography, this research will test a potentially overlooked physiological constraint on species’ elevational range shifts. 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.