QUANTITATIVE TRAIT LOCI RELATED TO DROSOPHILA SPECIATION

人们对物种形成的遗传学重新产生了兴趣，产生了许多理论和经验结果。 然而，大多数负责物种之间的形态/行为差异的多基因的定位研究有非常粗糙的分辨率，只有非常大的染色体片段的水平。 负责这些进化变化的实际基因是未知的。 果蝇交配选择的一个特征，雄性性梳，是一个理想的模型系统，为进一步的进展。 性选择已经在兄弟物种之间产生了差异，这些差异只表现出部分的合子后隔离，从而使遗传分析成为可能。 此外，负责性梳形成的生物化学和发育途径是最好理解的，具有大量的候选基因选择。 我们的长期目标是以性梳进化为模型，剖析种间差异的分子遗传基础。 我们将利用区域73 A-84 BD，已知贡献D之间齿数差异的一半。simulans和D.毛里求斯。 该区域也影响肛板、抱器和第5胸骨上的刚毛数量。 首先，我们将提高定位精度10倍，以确定这些影响是否是由于一个主基因的多效性效应，几个基因的性状特异性效应，或几个基因较小，加性或上位性，效果。 其次，我们将使用基于位点特异性P元件诱导的雄性重组的P元件跳跃和定位来鉴定这些数量性状基因（QTG）。 第三，我们将比较导致种内变异的等位基因和引起种间差异的等位基因。 我们将采集100份天然D。simulans的QTG等位基因，并将它们替换到100- 200 kbp染色体间隔内的其他相同的遗传背景中。 这将决定天然QTG等位基因效应的分布。 我们将鉴定在修饰性梳的QTG等位基因之间分离的分子多态性，并发现它们在D。simulans和D.毛里求斯。最后，我们将测试这些QTG等位基因是否有助于前和交配后物种之间的生殖隔离。 这种对几种性状遗传学的全面评估将进一步加深我们对物种形成遗传学的理解。

There has been renewed interest in the genetics of speciation, yielding many theoretical and empirical results. However, most mapping studies of polygenes responsible for morphological/behavioral differences between species have had very crude resolution, only down to the level of very large chromosome segments. The actual genes responsible for these evolutionary changes are unknown. A trait involved in Drosophila mating choice, male sex comb, is an ideal model system for further progress. Sexual selection has generated differences between sibling species that exhibit only partial postzygotic isolation, enabling genetic analysis. Moreover, the biochemical and developmental pathways responsible for sex comb formation are among the best understood, with a large choice of candidate genes. Our long-term goal is to dissect the molecular genetic basis of interspecific differences using sex comb evolution as a model. We will capitalize on the region 73A-84BD, known to contribute half of the tooth number difference between D. simulans and D. mauritiana. This region also affects bristle number on the anal plate, clasper, and the 5th sternite. First, we will increase the mapping precision ten fold to determine whether these effects are due to on e major gene with pleiotropic effects, several genes with trait-specific effects, or several genes with smaller, additive or epistatic, effects. Second, we will identify these quantitative trait genes (QTG) using P element hopping and mapping based on site-specific P element- induced male recombination. Third, we will compare the alleles contributing to intraspecific variation with those causing interspecific differences. We will sample 100 natural D. simulans QTG alleles and substitute them into the otherwise identical genetic background within 100-200kbp chromosome intervals. This will determine the distribution of effects of natural QTG alleles. We will identify molecular polymorphisms segregating between QTG alleles that modify sex comb, and find their frequencies in both D. simulans and D. mauritiana. Finally, we will test whether these QTG alleles contribute to pre- and postmating reproductive isolation between species. This comprehensive assessment of the genetics of several traits will further our understanding of the genetics of speciation.