Sex-specific genetic (co)variances of standard metabolic rate, body mass and locomotor activity in Drosophila melanogaster

A longstanding focus in evolutionary physiology concerns the causes and
consequences of variation in maintenance metabolism. Insight into this can
be gained by estimating the sex-specific genetic architecture of
maintenance metabolism alongside other, potentially correlated traits on
which selection may also act, such as body mass and locomotor activity.
This may reveal potential genetic constraints affecting the evolution of
maintenance metabolism. Here, we used a half-sibling breeding design to
quantify the sex-specific patterns of genetic (co)variance in standard
metabolic rate (SMR), body mass, and daily locomotor activity in
Drosophila melanogaster. There was detectable additive genetic variance
for all traits in both sexes. As expected, SMR and body mass were strongly
and positively correlated, with genetic allometry exponents (bA±se) of
0.66±0.16 in females and 0.58±0.32 in males. There was a significant and
positive genetic correlation between SMR and locomotor activity in males,
suggesting that alleles that increase locomotion have pleiotropic effects
on SMR. Sexual differences in the genetic architecture were driven in
large part by a difference in genetic variance in locomotor activity
between the sexes. Overall, genetic variation was mostly shared between
males and females, setting the stage for a potential intralocus sexual
conflict in the face of sexually antagonistic selection.