Collaborative Research: Evolution of Genetic Covariances in Stalk Eyed Flies

9411770锥形 种群生物学的一个基本问题是选择如何改变多个性状的组合。 人们早就知道，对一个性状的选择会引起未被选择的性状的相关变化。 这些相关的变化可以预测在短期内从性状的遗传方差和协方差统计估计从育种选择研究。 然而，要想预测几代之后的情况，就必须确定遗传协方差本身是如何变化的。 在这项研究中，研究人员建议调查选择的影响，一套11个形态和生活史性状的8个物种和8个选定的线的柄眼苍蝇之间的遗传协方差。 这些苍蝇提供了一个模型系统，研究这个问题，因为眼跨度二型性独立出现在至少四个属。 在单形物种中，相同体型的雄性和雌性的眼距相似，而在二形物种中，雄性的眼距超过体长。 通过从育种研究中估计遗传协方差，并将其与从DNA测序信息获得的系统发育关系进行比较，将能够确定当性状处于强定向选择下时遗传协方差变化的方向。 这些相关性研究将通过比较在实验室中经历了20多代定向选择的品系之间的遗传协方差来证实。 这项工作将产生三个主要结果：1）更好地了解非洲和东南亚有趣的蝇类群体之间的系统发育关系，其中一些是农业害虫; 2）新的统计方法用于比较协方差矩阵，比现有方法更稳健，假设更少，计算要求更低; 3）迄今为止最全面的分析，涉及遗传相关性是否作为自然选择的约束或结果。

9411770 Taper A fundamental question of population biology is how does selection alter suites of multiple traits. It has long been know that selection on one trait can cause correlated changes in traits not under selection. These correlated changes can be predicted over the short term from the among trait genetic variances and covariances statistics estimated from a breeding selection study. However, to make predictions beyond a few generations ones has to determine how the genetic covariances themselves change. In this study the investigators propose to investigate the influences of selection on the genetic covariances among a suite of 11 morphological and life history traits in eight species and eight selected lines of stalk-eyed flies. These flies provide a model system for studying this problem because eye span dimorphism has arisen independently in at least four genera. In monomorphic species males and females of equivalent body size have similar eye spans while in dimorphic species male eye span exceeds body length. By estimating genetic covariances from breeding studies and comparing they with respect to phylogenetic relationships obtained from DNA sequencing information that will be able to determine the rate of direction of genetic covariance change when a trait is under strong directional selection. These correlational studies will be corroborated by comparing genetic covariances among lines that have experienced directional selection for over 20 generations in a lab. This work will produce three major results: 1) an improved understanding of the phylogenetic relationships among intriguing group of flies from Africa and south-east Asia, some of which are agricultural pests; 2) new statistical methods for comparing covariance matrices which are more robust, make fewer assumptions and are less computationally demanding than the current methods; 3) the most comprehensive analysis yet performed relating to whether or not genetic correlations act as a constraint on or a consequ ence of natural selection.