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Incomplete genetic compensation and countergradient variation of blood-oxygen transport in deer mice

Velotta, Jonathan1

Published Nov 17, 2025 on Dryad. https://doi.org/10.5061/dryad.3r2280gw2

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Abstract

We combined lab and field data to quantify maladaptive (fitness-reducing) hematological responses to hypoxia and cold in deer mice (Peromyscus maniculatus) across their ~4000 m elevational range. In laboratory-raised mice native to low elevations, individuals increased their hemoglobin concentration and hematocrit in response to simulated high-elevation, a response that is maladaptive if unmitigated. In contrast, deer mice from high elevation increased hematocrit and hemoglobin to a lesser degree, consistent with genetic compensation. Unlike the predictions under complete genetic compensation, we observed a positive slope between hematological traits and elevation in the field, although this slope was lower than that observed in lowlanders in the lab. Our results suggest that deer mice have attenuated maladaptive hematological responses to high-elevation via genetic compensation that is incomplete, which has led to weak countergradient variation. We suggest this phenomenon is the result of a balance between positive selection for increased oxygen carrying capacity and antagonistic selection against elevated blood viscosity.