Natural Selection on Thermogenic Capacity of High-Altitude Deer Mice

Abstract

Adaptive explanations that rely on physiological arguments are common, but tests of hypotheses about the significance of whole-animal physiological performance (e.g., aerobic capacities) are rare. We studied phenotypic selection on the thermogenic capacity (i.e., maximal rate of oxygen consumption [V0 2 max] elicited via cold exposure) of high-altitude (-3800 m) deer mice (Peromyscus maniculatus). A high V0 2 max equates to a high capacity for heat production and should favor survival in the cold environments prevalent at high altitude. Strong directional selection favored high V0 2 max, at least in one year. The selection for increased V0 2 max is consistent with predictions derived from incorporating our physiological data into a biophysical model. During another year, we found weak evidence of selection for decreased body mass. Nonlinear selection was not significant for any of the selection episodes we studied. The strong directional selection for V0 2 max that we observed suggests that-given ample genetic variation-aerobic metabolism and perhaps endothermy may have evolved rapidly on the geological time scale.

Evolutionary and functional insights into the mechanism underlying high-altitude adaptation of deer mouse hemoglobin

“…These tradeoffs in O 2 -transport efficiency at different O 2 partial pressures (PO 2 's) suggest that the highaffinity ␣-globin genotype may confer highest fitness in highaltitude environments, whereas the low-affinity genotype may confer highest fitness in low-altitude environments (10)(11)(12)(13)(14). Consistent with this hypothesis, survivorship studies of freeranging deer mice demonstrated that aerobic performance is subject to strong directional selection at high-altitude (15) and electrophoretic surveys of ␣-globin polymorphism in deer mice from western North America revealed striking altitudinal patterns of allele frequency variation that are consistent with the predicted rank-order of genotypic fitnesses across environments: The high-affinity ␣-globin electromorph is present at high frequency in high-altitude populations (Ͼ2,750 m), whereas the low-affinity electromorph is either fixed or nearly fixed in low-altitude populations [Ͻ1,750 m; (16)]. Moreover, patterns of nucleotide diversity and linkage disequilibrium (LD) at the two HBA paralogs are indicative of spatially varying selection between high-and low-altitude populations (17,18).…”

A strong response to selection on mass-independent maximal metabolic rate without a correlated response in basal metabolic rate

“…Its central importance is reflected in the thousands of studies published on energy metabolism (Houston et al, 1993;Hayes and O'Connor, 1999;Speakman, 2008; Burton et al, 2011, Konarzewski andKsiążek, 2013;White and Kearney, 2013). Despite these studies, many questions about metabolic rates and energy metabolism remain unanswered.…”

Variation and homogeneity in affective responses to physical activity of varying intensities: An alternative perspective on dose – response based on evolutionary considerations

“…In a preliminary observational study of a population of contemporary hunter-gatherers (the Ache of eastern Paraguay), Kaplan and Hill (1985) found that, among males, hunting ability (presumed to be a composite of skill and the ability to pursue prey) was associated with increased reproductive success, defined as survivorship of offspring. Additional support comes from animal research (Hayes & O'Connor, 1999;Jayne & Bennett, 1990). Studies show that the amount of time a constant speed can be sustained (i.e.…”