Data from: Genetic and environmental effects on the scaling of metabolic rate with body size

Metabolic rate (MR) often scales with body mass (BM) following a power
function of the form MR = aBMb, where b is the allometric exponent (i.e.
slope on a log-log scale). The variational properties of b have been
debated, but very few studies have tested for genetic variance in b, and
none have tested for a genotype-by-environment (GxE) interaction in b.
Consequently, the short-term evolutionary potentials of both b and its
phenotypic plasticity remain unknown. Using 10 clones of a population of
Daphnia magna, we estimated the genetic variance in b and assessed whether
a GxE interaction affected b. We measured metabolic rate on juveniles of
different sizes reared and measured at three temperatures (17, 22 and
28&[deg]C). Overall, b decreased with increasing temperature. We
found no evidence of genetic variance in b at any temperature, and thus no
GxE interaction in b. However, we found a significant GxE interaction in
size-specific metabolic rate. Using simulations, we show how this GxE
interaction can generate genetic variation in the ontogenetic allometric
slopes of animals experiencing directional changes in temperature during
growth. This suggests that b can evolve despite having limited genetic
variation at constant temperatures.