NATURAL SELECTION ON THERMOGENIC CAPACITY OF HIGH-ALTITUDE DEER MICE

Area of Science:

• Evolutionary Biology
• Physiological Ecology
• Animal Physiology

Background:

• Adaptive explanations often cite physiological traits, but empirical tests linking whole-animal performance to selection are infrequent.
• High-altitude environments pose challenges requiring physiological adaptations for survival, such as thermoregulation.

Purpose of the Study:

• To investigate phenotypic selection on thermogenic capacity, measured as maximal oxygen consumption (VO2 max), in high-altitude deer mice.
• To test the hypothesis that a high VO2 max confers a survival advantage in cold, high-altitude conditions.

Main Methods:

• Studied phenotypic selection on VO2 max in deer mice (Peromyscus maniculatus) at approximately 3800 m elevation.
• Measured VO2 max via cold-induced oxygen consumption to assess thermogenic capacity.
• Analyzed selection gradients for VO2 max and body mass over multiple years.

Main Results:

• Observed strong directional selection favoring higher VO2 max in at least one study year.
• Found weak evidence for selection against decreased body mass in another year.
• No significant nonlinear selection was detected for any studied selection episode.

Conclusions:

• The strong directional selection for VO2 max supports its importance for survival in high-altitude, cold environments.
• Results are consistent with biophysical model predictions incorporating physiological data.
• Suggests that aerobic metabolism and endothermy may evolve rapidly given sufficient genetic variation.