Collaborative Research: Evolution of Genetic Covariances in Stalk Eyed Flies

[9411770 .锥度]种群生物学的一个基本问题是选择如何改变多种性状的组合。人们早就知道，对一个性状的选择会导致未被选择性状的相关变化。这些相关变化可以通过性状间遗传方差和从育种选择研究中估计的协方差统计来预测。然而，要预测几代以后的情况，就必须确定遗传协方差本身是如何变化的。在本研究中，研究了选择对8个种8个系的11个形态和生活史性状遗传协方差的影响。这些果蝇为研究这一问题提供了一个模型系统，因为至少在四个属中独立出现了眼距二态性。在单形种中，体型相等的雄性和雌性具有相似的眼展，而在二形种中，雄性的眼展超过了体长。通过从育种研究中估计遗传协方差，并将其与从DNA测序信息中获得的系统发育关系进行比较，将能够确定当性状处于强方向选择下时遗传协方差变化的方向速率。这些相关研究将通过在实验室中比较经历了20多代方向选择的系之间的遗传协方差得到证实。这项工作将产生三个主要结果：1)提高对来自非洲和东南亚的有趣的苍蝇群（其中一些是农业害虫）之间的系统发育关系的理解；2)比较协方差矩阵的新统计方法比现有方法更稳健、假设更少、计算量更少；3)关于遗传相关性是否作为自然选择的约束或结果的最全面的分析。

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.