Postdoctoral Fellowship: OCE-PRF: Understanding population-level genomic and evolutionary impacts of climate change in an anadromous fish species relying on natal homing

Cornell University, Ithaca NY

Investigators

Abstract

Range shifts at the species level associated with climate change have been observed and proposed in many taxa, where a species will typically move its range towards favorable temperatures in the direction of the nearest pole. However, genetic subdivision along a species’ range is also commonly observed, which may imply that subpopulations are on different evolutionary trajectories due to things like natural selection and local adaptation. Despite observing species range shifts in many taxa, we have yet to document climate-induced poleward range shifting at this subpopulation level due to the difficulty in doing so. This project aims to use time series genetic data within an anadromous fish system to observe poleward range shifting at the subpopulation level for a species. Anadromous fish are born in freshwater environments, live most of their lives in a marine environment, and return to the same freshwater systems where they were born to breed. The return to specific freshwater environments can be leveraged as a self-sorting mechanism where we are able to sample the fish in their natal rivers across two different points in time and assess if their genes have migrated poleward in that time. The PI will broaden participation in science by mentoring undergraduate and early-career graduate students and by participating in outreach events at local nature centers associated with the communities impacted by the collapse of American shad populations. Genetic drift and selection are the two main factors governing allele frequencies in populations and identifying temporal and spatial trends in each provides insights into the evolutionary drivers of populations or species. Spatial differentiation may suggest e.g., isolation by distance or local adaptations along clines, however temporal differentiation may be driven by e.g., cohort effects, drift, or changing selection pressures. I will use the American shad study system to characterize discrete population-level latitudinal range shifts identified by assessing spatiotemporal variation in neutral and adaptive differentiation across river systems they return to for spawning. To accomplish this, I will examine samples spanning 20 years using linked-read whole genome sequencing to address the following question: Have individual American shad populations shifted their distributions poleward? This question can be decomposed into three specific inquiries: (Q1) Is straying to breed in non-natal rivers stochastic or directional? (Q2) Have there been population-level shifts in neutral differentiation spanning multiple generations? (Q3) Have there been population-level shifts in adaptive differentiation spanning multiple generations? 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.