Ph.D. in Zoology 1994
Dissertation title: Quantitative genetics of locomotor performance and physiology in house mice (Mus domesticus)
xv + 264 pages.
The goal of this research was to test two long-standing
evolutionary hypotheses derived from the comparative and ecological physiology
literature: (1) Locomotor speed and stamina show a necessary
trade-off; (2) Maximal and basal rates of aerobic metabolism are functionally
coupled. We studied randombred house mice (Mus domesticus)
of the Hsd:ICR strain as a model mammalian system. We used a combined
parent-offspring, half-sib, full-sib breeding design, with crossfostering,
to estimate addictive genetic variances and covariance for maximal sprint
running speed and swimming endurance. Effects of various continuous
and categorical covariates were controlled statistically by computing residuals
from multiple regression equations. Neither speed nor endurance was
significantly correlated with body mass, either phenotypically or genetically.
Residual sprint speed and swimming endurance were not phenotypically correlated.
However, additive genetic correlations between sprint speed on trial day
one and measures of endurance were negative and statistically different
from zero. These results provide partial support for the hypothesis
of a necessary trade-off between these two aspects of locomotor abilities.
Maximal (VO2max) and basal (BMR) rates of oxygen consumption may be functionally coupled in vertebrates because they share some common physiological pathways. Both exercise-induced VO2max and BMR (both mass-corrected) had low heritability. Neither phenotypic nor genetic correlations were statistically different from zero. Therefore, we found no evidence for positive coupling between VO2max and BMR in these mice.
We also compared aspects of locomotor performance and metabolism in wild and random-bred laboratory house mice and their reciprocal crosses using a ýcommon gardenţ experiment. Analysis of covariance indicated that wild and hybrid mice exhibited higher forced maximal sprint running speeds, higher mass-corrected maximal rates of oxygen consumption during forced exercise, ran significantly more on voluntary activity wheels, and had greater relative ventricle masses than did lab mice. No significant differences were found for relative gastrocnemius muscle mass, liver mass, hematocrit, or blood hemoglobin content.