QUANTITATIVE GENETICS OF SPRINT RUNNING SPEED AND SWIMMING ENDURANCE IN LABORATORY HOUSE MICE (MUS DOMESTICUS)

Abstract

We tested the hypothesis that locomotor speed and endurance show a negative genetic correlation using a genetically variable laboratory strain of house mice (Hsd:ICR: Mus domesticus). A negative genetic correlation would qualify as an evolutionary "constraint," because both aspects of locomotor performance are generally expected to be under positive directional selection in wild populations. We also tested whether speed or endurance showed any genetic correlation with body mass. For all traits, residuals from multiple regression equations were computed to remove effects of possible confounding variables such as age at testing, measurement block, observer, and sex. Estimates of quantitative genetic parameters were then obtained using Shaw's (1987) restricted maximum-likelihood programs, modified to account for our breeding design, which incorporated cross-fostering. Both speed and endurance were measured on two consecutive trial days, and both were repeatable. We initially analyzed performances on each trial day and the maximal value. For endurance, the three estimates of narrow-sense heritabilities ranged from 0.17 to 0.33 (full ADCE model), and some were statistically significantly different from zero using likelihood ratio tests. The heritability estimate for sprint speed measured on trial day 1 was 0.17, but negative for all other measures. Moreover, the additive genetic covariance between speeds measured on the two days was near zero, indicating that the two measures are to some extent different traits. The additive genetic covariance between speed on trial day 1 and any of the four measures of endurance was negative, large, and always statistically significant. None of the measures of speed or endurance was significantly genetically correlated with body mass. Thus, we predict that artificial selection for increased locomotor speed in these mice would result in a decrease in endurance, but no change in body mass. Such experiments could lead to a better understanding of the physiological mechanisms leading to trade-offs in aspects of locomotor abilities.

A Quantitative Genetic Test of Adaptive Decoupling Across Metamorphosis for Locomotor and Life-History Traits in the Pacific Tree Frog, Hyla Regilla

“…1993; Sorci et al 1995). Dohm et al (1996), who account for most nonadditive genetic variance in a sample of mice, report a heritability for burst speed of 0.17, a value similar to the narrow-sense estimates in Table 4.…”

“…Interindividual variation in locomotor performance is temporally repeatable (see table 1 of Austin and Shaffer 1992), is subject to selection in some populations (Jayne and Bennett 1990;Swain 1992;Watkins 1996), and often has some heritable genetic component (Garland 1988;Tsuji et al 1989;Sorci et al 1995;Dohm et al 1996). On the basis of these findings, Carrier (1996) proposed that adult locomotor performance often evolves primarily in response to selection on juveniles, a hypothesis that requires a genetic correlation between juvenile and adult performance.…”

Selected Contribution: Variation and heritability for the adaptational response to exercise in genetically heterogeneous rats

“…The single best trial of three was used because it was deemed the best indicator of capacity determined by intrinsic genetic composition (9). This idea of estimating the genetic component from the one best day of performance, rather than the average for all trials, for example, has two origins.…”

Locomotor trade-offs in mice selectively bred for high voluntary wheel running

“…After the wheel test, mice were chased along a photocell-lined racetrack to determine apparent maximal sprint speed, following standard procedures for small rodents (Djawdan and Garland, 1988;Garland et al, 1988;Friedman et al, 1992;Dohm et al, 1994;Garland et al, 1995;Dohm et al, 1996). Wheel measurements and sprint speed were, on average, 11.3 days apart.…”