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Data from: Local adaptation expands genetic variation in the thermal performance of a coastal fish: Implications for ocean warming

Lundquist, Alexis1; Cole, Thea1; Johnson, Darren1

Published Sep 17, 2026 on Dryad. https://doi.org/10.5061/dryad.0k6djhbhp

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Abstract

Species’ responses to climate change can include a component of contemporary evolution, and such responses can be important in offsetting the detrimental effects of warming. However, the capacity of populations to evolve will depend on the level of genetic variation underlying traits affected by climate change. It is not always clear how such variation is maintained, but one plausible mechanism involves adaptation of subpopulations to local climate conditions. In this study, we experimentally tested whether populations of a coastal fish, the California Grunion, exhibited inherited differences in thermal reaction norms (measured as the family-average values of growth and mortality across a range of temperatures). We also quantified the degree to which differentiation among locations increased the amount of genetic variation underlying thermal reaction norms within the population at large. We collected gametes from three local populations that were separated by an average of 150km and located along a north-south cline. Eggs from each population were fertilized in a breeding experiment that allowed us to quantify genetic variation and heritability. Larvae from all three populations were reared in a common laboratory environment and across temperatures reflecting their natural range. Patterns of growth exhibited inherited differences in that offspring from higher latitude populations grew faster on average when reared in identical conditions. Offspring from different source populations varied significantly in how sensitive their mortality rates were to temperature, and offspring from parents in the lowest latitude population had lower mortality rates at high temperatures. When growth and mortality rates were combined to express biomass, we saw evidence of both counter gradient variation (greater production from high latitude populations) and local adaptation in thermal specialization (peak production occurred at higher temperatures for the lowest latitude population). Genetic variation among locations increased the total amount of genetic variation within the broader metapopulation. Even when considering only three subpopulations, broad sense heritability values were increased for both growth and mortality rate by factors of 1.07 and 1.1 respectively. Our results emphasize that metapopulation-level processes can play important roles in both the promotion of genetic variation, and the response to selection generated by climate change.