The quantitative genetics of maximal and basal rates of oxygen consumptionin alice

A positive genetic correlation between basal metabolic rate (BMR) and maxim al ((V) over dotO(2)max) rate of oxygen consumption is a key assumption of the aerobic capacity model for the evolution of endothermy. We estimated th e genetic (V-A, additive, and V-D, dominance), prenatal (V-N), and postnata l common environmental (V-E) contributions to individual differences in met abolic rates and body mass for a genetically heterogeneous laboratory strai n of house mice (Mus domesticus). Our breeding design did not allow the sim ultaneous estimation of V-D and V-N. Regardless of whether V-D or V-N was a ssumed, estimates of V-A were negative under the full models. Hence, we fit ted reduced models (e.g., V-A + V-N + V-E or V-A + V-E) and obtained new va riance estimates. For reduced models, narrow-sense heritability (h(N)(2)) f or BMR was <0.1, but estimates of h(2)(N) for (V) over dotO(2)max were high er. When estimated with the V-A + V-E model, the additive genetic covarianc e between (V) over dotO(2)max and BMR was positive and statistically differ ent from zero. This result offers tentative support for the aerobic capacit y model for the evolution of vertebrate energetics. However, constraints im posed on the genetic model may cause our estimates of additive variance and covariance to be biased, so our results should be interpreted with caution and tested via selection experiments.