物种形成的关键步骤是产生生殖隔离，而杂交不亲和是实现生殖隔离的一种重要形式。转座元件和piRNA之间的军备竞争是基因组冲突的一种重要方式，也是产生杂交不亲和的一种重要方式。本研究在微进化水平上研究转座元件和piRNA相互作用的一些基本生物学问题：1）宿主如何产生piRNA抑制转座元件的入侵？2）适应性进化是否驱动转座元件和piRNA共进化? 3）转座元件和piRNA的相互作用导致的杂交不亲和在自然界中是否具有普遍性？4）杂交不亲和能否导致物种形成？这是本课题所要研究的问题。通过对来自五大洲的黑腹果蝇品系全基因组序列分析，我们将结合piRNA深度测序和群体遗传学理论对上述问题进行探讨。在群体基因组学和高通量测序分析的基础上，我们将进行大规模的果蝇杂交和实验来验证理论预测。本研究旨在从转座元件和piRNA相互作用这个角度在微观进化水平上探究杂交不育的原因和规律，有助于深入理解物种形成新规律。

Reproductive isolation is a key component of speciation. Hybrid incompatibility is an important mechanism that leads to reproductive isolation. The arms-race between transposable elements (TEs) and piRNAs is a basic format of genomic conflict, which usually causes hybrid incompatibility. We aim to study the fundamental biological questions that are related to the interplays between TEs and piRNAs at the micro-evolutionary level. The questions we are addressing include: 1) how do the host develops piRNAs to defend TE invasion？ 2 Will adaptive evolution drive co-evolution between TEs and piRNA at intra- and inter-species level? 3) How common is the hybrid dysgenesis caused by the interaction between TEs and piRNA? 4) Will hybrid incompatibility leads to new species formation? By integrating extensive population genomic analysis and piRNA deep sequencing, we will address the aforementioned questions in this study. To verify the predictions derived from the results of population genomics and piRNA sequencing, we will carry out large scale crossing of fly strains that differ in the composition of TEs and piRNAs. We aim to reveal the general rules for hybrid incompatibility caused by the interaction of TEs and piRNAs at micro-evolutionary level. Our results will improve our understanding on the mechanisms of reproductive isolation and speciation.