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Dryad

Coordinated changes across the O2 transport pathway underlie adaptive increases in thermogenic capacity in high-altitude deer mice

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May 08, 2020 version files 54.50 KB
Feb 15, 2024 version files 117.75 KB

Abstract

Animals native to the hypoxic and cold environment at high altitude provide an excellent opportunity to elucidate the integrative mechanisms underlying the adaptive evolution of complex traits. The capacity for aerobic thermogenesis can be a critical determinant of survival for small mammals at high altitude, but the physiological mechanisms underlying the evolution of thermogenic capacity remain unresolved. We examined this issue by comparing high-altitude deer mice (Peromyscus maniculatus) to low-altitude deer mice and white-footed mice (P. leucopus). Mice were bred in captivity and adults were acclimated to each of four treatments: warm (25°C) normoxia; warm hypoxia (12 kPa O2); cold (5°C) normoxia; or cold hypoxia. Acclimation to hypoxia and/or cold increased thermogenic capacity, but hypoxia acclimation led to much greater increases in thermogenic capacity in highlanders than in lowlanders. The high thermogenic capacity of highlanders was associated with increases in pulmonary O2 extraction, arterial O2 saturation, cardiac output, stroke volume, and arterial-venous O2 difference. These mechanisms underlying the evolution of enhanced thermogenic capacity in highlanders were partially distinct from those underlying the ancestral acclimation responses of lowlanders. Environmental adaptation has thus enhanced phenotypic plasticity and expanded the physiological toolkit for coping with the challenges at high altitude.