Sexual selection moderates heat stress response in males and females

1. A widespread effect of climate change is the displacement of organisms
from their thermal optima. The associated thermal stress imposed by
climate change has been argued to have a particularly strong impact on
male reproduction but evidence for this postulated sex-specific stress
response is equivocal. 2. One important factor that may explain intra- and
interspecific variation in stress responses is sexual selection, which is
predicted to magnify negative effects of stress. Nevertheless, empirical
studies exploring the interplay of sexual selection and heat stress are
still scarce. 3. We tested experimentally for an interaction between
sexual selection and thermal stress in the red flour beetle Tribolium
castaneum by contrasting heat responses in male and female reproductive
success between setups of enforced monogamy versus polygamy. 4. We found
that polygamy magnifies detrimental effects of heat stress in males but
relaxes the observed negative effects in females. Our results suggest that
sexual selection can reverse sex differences in thermal sensitivity, and
may therefore alter sex-specific selection on alleles associated with heat
tolerance. 5. Assuming that sexual selection and natural selection are
aligned to favour the same genetic variants under environmental stress,
our findings support the idea that sexual selection on males may promote
the adaptation to current global warming.