NSF PRFB FY 2023: Thermoregulatory evolution of hummingbirds: Using urban heat islands as a globally replicated natural experiment

Alaasam, Valentina, Reno NV

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2023, Integrative Research Investigating the Rules of Life Governing Interactions Between Genomes, Environment, and Phenotypes. The fellowship supports research and training of the fellow that will contribute to the area of Rules of Life in innovative ways. Species are facing rapid changes in ambient temperature due to changing climate. To survive, organisms will need to adjust their physiology through a combination of phenotypic change and genetic change. Whether the rate and magnitude of these responses can match changes across environments with varying temperatures will determine whether populations persist or go locally extinct. This fellowship uses cities to study evolutionary responses to changing ambient temperatures on contemporary timescales. Replacement of vegetation with paved surfaces creates an Urban Heat Island (UHI) effect where mean and extreme temperatures are higher compared to undisturbed surroundings. The UHI effect is a nearly universal characteristic of cities worldwide, resulting in well-distributed, globally-replicated thermal gradients. By linking environmental, phenotypic, and genetic variation, results will shed light on the fundamental processes underlying the persistence, evolutionary potential, and genetic divergence of endothermic species facing warmer climates. By testing hypotheses in four cities across a latitudinal gradient, this project will determine how environmental context will shape evolutionary outcomes. The fellow will investigate how urban heat is affecting the evolution of complex thermoregulatory traits and genetic divergence in hummingbirds, a model taxon for detecting population-level responses to changing climate. Hummingbirds have some of the highest mass-specific metabolisms of all endotherms and store very little fat, making them particularly sensitive to changes in temperature and instrumental for detecting population-level responses to changing climate. The fellow will measure morphology, behavior (torpor use), thermal tolerance (using respirometry), and daily energy expenditure (using doubly-labeled water) of paired urban and non-urban hummingbird populations. Using next-generation sequencing, the fellow will then conduct a genome-wide association study to identify regions of the genome that may be under selection by urban heat. Studies will be conducted in four cities across a latitudinal gradient to describe how the flexibility of thermoregulatory traits and resulting evolutionary potential may vary across latitudes. And by engaging with local communities, the outcomes of this research will contribute to designing greener cities that both promote biodiversity and reduce the negative impacts of urban heat on underserved human communities. 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.