Do genomic regions under selection have hybrid origins in cichlids?

杂交越来越被认为是一种创造性的进化力量，因为从一个物种可以很容易地从另一个物种获得生态上有用的基因组属性，而无需等待突变和固定。然而，我们目前缺乏证据表明这种遗传贡献可以通过自然选择优先保留——杂交可能是物种形成的结果而不是原因。特别是，在适应性辐射中，杂交在数百种物种的产生中所起的作用尚不清楚。基因组技术的最新进展使详细研究这一过程成为一种令人兴奋的可能性——DNA技术可以识别“物种形成的基因组岛”——选择下的位点（或与选择下的区域相连），这些位点显示了物种之间相对于基因组其余部分的差异。至关重要的是，这些来自不同创始谱系的重要遗传区域的遗传贡献可以在适应性辐射中确定。在这个提案中，我计划证明“教科书”马拉维湖慈鲷鱼辐射由来自不同来源的适应性重要基因组区域的集合组成。该项目将利用最近的白顿星罗非鱼（Astatotilapia burtoni cichlid）基因组序列，通过一次对20多个物种进行全基因组筛选，从而利用rad标签测序来识别数以万计的单核苷酸多态性（snp），从而提高我们的认识。基因组扫描将确定基因组中对适应性重要的区域，然后我将测试这些区域在地方性辐射谱系中是否显示出与假定的播种谱系杂交的信号，与“中性”区域相比。这种方法将首次证明在适应性辐射中选择的位点具有不同的起源，证实了杂交作为适应性变化驱动力的重要性。

Hybridization is increasingly recognised as a creative evolutionary force because ecologically useful genomic attributes from one species can be easily obtained from another without waiting for mutation and fixation. However, we currently lack evidence that such genetic contributions could be preferentially retained through natural selection- hybridization maybe a consequence rather than a cause of speciation. In particular, the role that hybridization plays in the generation of hundreds of species in adaptive radiations is unclear. Recent advances in genome technologies make studying this process in detail an exciting possibility - DNA technology can identify "genomic islands of speciation"- loci under selection (or linked to regions under selection) which show divergence between species relative to the rest of the genome. Crucially, the genetic contributions of these adaptively important genetic regions from divergent founding lineages can then be identified in adaptive radiations. In this proposal, I plan to demonstrate that the "text book" Lake Malawi cichlid fish radiation consists of collections of adaptively important genomic regions from different sources. The project will capitalise on the recent Astatotilapia burtoni cichlid genome sequence, advancing our understanding by genome-wide screening of more than 20 species at once in order to identify tens of thousands of single nucleotide polymorphisms (SNPs) using RAD-tag sequencing. Genome scans will identify regions of the genome important in adaptation, and I will then test whether these regions in the endemic radiation lineages show a signal of hybridization with putative seeding lineages, compared to "neutral" regions. This approach will be the first evidence to demonstrate that loci under selection in an adaptive radiation have distinct origins, confirming the importance of hybridization as a driving force for adaptive change.