A team of mountaineering mice has provided valuable insights into how evolutionary adaptation to localized conditions can enable a single species to thrive across diverse environments. Led by Naim Bautista, a postdoctoral researcher at the University of Nebraska-Lincoln, the study focused on highland deer mice and their lowland counterparts. The mice were taken on a simulated ascent to 6,000 meters, with Bautista tracking how they responded to cold stress at progressively lower oxygen levels. The goal was to determine whether the mice could thrive across a broad range of elevations by evolving adaptations to local conditions or by possessing a generalized ability to acclimatize.
The study, conducted at McMaster University in Canada, divided the mice into control groups that remained at sea level and acclimation groups that undertook the seven-week ascent. As the mice ascended, oxygen levels were reduced to mimic what climbers would experience, and their ability to cope with cold exposure was monitored by measuring metabolic heat production. The results showed that highland and lowland deer mice do not share a general ability to acclimate to hypoxia. Highland mice had better regulation of body temperature than lowland mice as oxygen levels dropped, due to more efficient breathing and circulatory oxygen transport.
One of the key findings of the study was that highland mice have a genetic advantage that helps suppress thickening of the right ventricle of the heart, a symptom of pulmonary hypertension common among lowland mammals forced to acclimatize to low oxygen conditions. This genetic advantage allows the highland mice to thrive in their high-altitude environments. Bautista emphasized that the study demonstrates how adaptation to local conditions can enable a widely distributed species like the deer mouse to thrive in diverse environments.
The researchers plan to repeat the study with the yellow-rumped leaf-eared mouse, the world’s highest-dwelling mammal, found in the Andes mountains at elevations up to 22,110 feet. This species was discovered by the lead researcher, Jay Storz, and the study aims to measure the responses of these mice to changing environmental conditions. The team also includes researchers from McMaster University, the University of Montana, and the University of British Columbia. The findings of the deer mice study were published in the Proceedings of the National Academy of Sciences (PNAS), showcasing how evolved changes specific to populations can influence their flexibility and ability to survive in different habitats.