Maintenance costs of male dominance and sexually antagonistic selection in the wild
Résumé
1. Variation in dominance status determines male mating and reproductive success, but
natural selection for male dominance can be detrimental or antagonistic for female per-
formance, and ultimately their fitness. Attaining and maintaining a high dominance status
in a population of competing individuals is physiologically costly for males. But how male
dominance status is mediated by maintenance energetics is currently not well under-
stood, nor are the corresponding effects of male energetics on his sisters recognized.
2. We conducted laboratory and field experiments on rodent populations to test
whether selective breeding for male dominance status (dominant vs. subordinate
breeding lines) antagonistically affected basal metabolic rate (BMR) and fitness of
females under wild conditions.
3. Our results showed elevated BMR in females, but not in males, from the dominant
breeding line. However, phenotypically dominant males from the subordinate
breeding line had the highest BMR.
4. Males from the dominant line with low BMR sired the most litters and offspring in
the field. Similarly, females from the dominant selection line tended to have more
offspring if they had lower BMR, while the opposite trend was found in females
from the subordinate selection line. Females with high and low BMR reproduced
most often, as indicated by a significant quadratic selection gradient.
5. The increased female BMR resulting from selection for male dominance suggests
genetic incompatibility between sexes in metabolism inheritance. Elevated BMR
in behaviourally dominant males, but not in males from the dominant breeding
line, suggests physiological costs in males not genetically suited for dominance.
6. Fitness costs of elevated maintenance costs (measured as BMR) shown here sup-
port the energetic compensation hypothesis where high BMR is selected against
as it would trade off energy required for other important life-history attributes.