Dohm Michael R, Hayes Jack P, Garland Theodore
Department of Zoology, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin, 53706.
Department of Biology, University of Nevada, Reno, Nevada, 89557.
Evolution. 1996 Aug;50(4):1688-1701. doi: 10.1111/j.1558-5646.1996.tb03940.x.
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.
我们使用具有遗传变异性的实验小鼠品系（Hsd:ICR: 小家鼠）来检验运动速度和耐力呈现负遗传相关性这一假设。负遗传相关性可被视为一种进化“限制”，因为在野生种群中，运动表现的这两个方面通常都预期受到正向定向选择。我们还检验了速度或耐力是否与体重存在任何遗传相关性。对于所有性状，通过计算多元回归方程的残差来消除可能的混杂变量的影响，如测试时的年龄、测量批次、观察者和性别。然后使用肖（1987年）的限制最大似然程序获得数量遗传参数的估计值，并针对我们纳入交叉寄养的育种设计进行了修改。速度和耐力均在连续两天的试验日进行测量，且两者都具有重复性。我们最初分析了每个试验日的表现以及最大值。对于耐力，狭义遗传力的三个估计值范围为0.17至0.33（完整的ADCE模型），并且使用似然比检验时，其中一些与零存在统计学显著差异。在试验日1测量的短跑速度的遗传力估计值为0.17，但其他所有测量值均为负。此外，两天测量的速度之间的加性遗传协方差接近零，表明这两个测量值在某种程度上是不同的性状。试验日1的速度与任何四个耐力测量值之间的加性遗传协方差均为负、较大且始终具有统计学显著性。速度或耐力的任何测量值与体重均无显著的遗传相关性。因此，我们预测，对这些小鼠进行增加运动速度的人工选择将导致耐力下降，但体重不变。此类实验可能有助于更好地理解导致运动能力各方面权衡的生理机制。
