Blouin Michael S
Department of Biological Science, Florida State University, Tallahassee, FL, 32306-2043, USA.
Evolution. 1992 Jun;46(3):735-744. doi: 10.1111/j.1558-5646.1992.tb02079.x.
It is often proposed that the morphometric shape of animals often evolves as a correlated response to selection on life-history traits such as whole-body growth and differentiation rates. However, there exists little empirical information on whether selection on rates of growth or differentiation in animals could generate correlated response in morphometric shape beyond that owing to the correlation between these rates and body size. In this study genetic correlations were estimated among growth rate, differentiation rate, and body-size-adjusted head width in the green tree frog, Hyla cinerea. Head width was adjusted for size by using the residuals from log-log regressions of head width on snout-vent length. Size-adjusted head width at metamorphosis was positively genetically correlated with larval period length. Thus, size-independent shape might evolve as a correlated response to selection on a larval life-history trait. Larval growth rate was not significantly genetically correlated with size-adjusted head width. An additional morphometric trait, size-adjusted tibiofibula length, had a nonnormal distribution of breeding values, and so was not included in the analysis of genetic correlations (offspring from one sire had unusually short legs). This result is interesting because, although using genetic covariance matrices to predict long-term multivariate response to selection depends on the assumption that all loci follow a multivariate Gaussian distribution of allelic effects, few data are available on the distribution of breeding values for traits in wild populations. Size at metamorphosis was positively genetically correlated with larval period and larval growth rate. Quickly growing larvae that delay metamorphosis therefore emerge at a large size. The genetic correlation between larval growth rate and juvenile (postmetamorphic) growth rate was near zero. Growth rate may therefore be an example of a fitness-related trait that is free to evolve in one stage of a complex life cycle without pleiotropic constraints on the same trait expressed in the other stage.
人们常提出，动物的形态测量形状通常作为对诸如全身生长和分化速率等生活史特征选择的相关反应而进化。然而，关于动物生长或分化速率的选择是否能在形态测量形状上产生超出这些速率与体型之间相关性的相关反应，几乎没有实证信息。在本研究中，估计了绿树蛙（Hyla cinerea）的生长速率、分化速率和体型调整后的头部宽度之间的遗传相关性。通过使用头部宽度对吻肛长度的对数-对数回归残差来对头部宽度进行体型调整。变态时体型调整后的头部宽度与幼体期长度呈正遗传相关。因此，与体型无关的形状可能作为对幼体生活史特征选择的相关反应而进化。幼体生长速率与体型调整后的头部宽度没有显著的遗传相关性。另一个形态测量特征，体型调整后的胫腓骨长度，其育种值分布不正常，因此未纳入遗传相关性分析（来自一个父本的后代腿部异常短）。这个结果很有趣，因为尽管使用遗传协方差矩阵来预测对选择的长期多变量反应依赖于所有基因座遵循等位基因效应的多变量高斯分布这一假设，但关于野生种群中性状育种值分布的数据很少。变态时的体型与幼体期和幼体生长速率呈正遗传相关。因此，延迟变态的快速生长幼体以较大体型出现。幼体生长速率与幼体（变态后）生长速率之间的遗传相关性接近零。因此，生长速率可能是一个与适合度相关的性状的例子，它可以在复杂生命周期的一个阶段自由进化，而对另一阶段表达的相同性状没有多效性限制。
