Adaptive radiations of New World lupins revealed by transcriptome sequencing

自达尔文和华莱士的开创性工作以来，对适应性辐射的研究——适应非常不同条件的密切相关物种群体——对我们对进化的理解产生了重要的见解。物种最近的快速辐射可以用作模型，使我们能够研究在我们星球历史上主要适应性辐射期间起作用的一般进化过程。适应性辐射发生的条件还没有得到很好的理解，一般来说，人们也不清楚为什么有些生物群体物种非常丰富，而另一些生物群体尽管年龄相似，但物种却很少。适应性辐射可以在很短的时间内形成，例如，物种丰富的非洲慈鲷群只有几千年的历史，这种群体的物种形成率非常高，然而，这种快速（“爆炸性”）物种形成的一般原因需要进一步调查。该项目致力于分析一个植物属（豆科）在多重快速辐射中的进化遗传过程，该属在植物中表现出一些已知的最高净多样化率。安第斯羽扇豆的物种多样化速度惊人，在过去的180万年里进化了85个物种。一种独立的羽扇豆猴谱系正在北美活跃地传播。这种可复制的辐射提供了强有力的比较系统，以解决有关驱动多样化事件的进化力量的问题。以前没有对重复快速辐射进行详细的进化遗传分析。尽管最近分化的西半球羽扇豆属物种的序列分化程度相对较低，但其生命形式（从矮小的一年生植物和匍匐草本植物到小树）的范围和所占据的栖息地是惊人的。这种加速的形态和生态多样化表明，许多基因可能经历了强烈的适应选择。该项目的目的是解决目前尚未解决的问题，即在适应性辐射中参与适应的基因类型，以及氨基酸水平与调节区域的选择的相对作用。这将涉及比较DNA序列分化和基因表达模式之间的密切相关和最近分化的物种，不同的生命形式和适应一系列的环境。通过Solexa/Illumina测序获得全基因组DNA多态性/差异和表达数据。这将对安第斯山脉和北美的积极辐射分支以及一组在积极辐射分支之外的物种进行比较。

Studies of adaptive radiations - groups of closely related species adapted to very different conditions - have yielded important insights into our understanding of evolution ever since the pioneering works of Darwin and Wallace. Rapid recent radiations of species can be used as models allowing us to study general evolutionary processes that were at work during the major adaptive radiations in the history of our planet. The conditions under which adaptive radiations occur are not well understood and generally it is not clear why some groups of organisms are very species-rich, while others consist of only few species despite similar age. Adaptive radiations can form in a very short period of time, e.g. species-rich groups of African cichlids are only few thousand years old and speciation rates in such groups is very high, yet general reasons for such rapid ('explosive') speciation require further investigation. This project is devoted to the analysis of evolutionary genetic processes during multiple rapid radiations in a plant genus Lupinus (Leguminosae), which exhibits some of the highest known rates of net diversification in plants. Exceptional rates of species diversification have been documented for Andean lupins, where 85 species have evolved in the last 1.8 million years. An independent lineage of lupins is actively radiating in North America. Such replicate radiations provide powerful comparative systems to address questions about the evolutionary forces driving episodes of diversification. Detailed evolutionary genetic analysis of replicate rapid radiations has not been undertaken previously.Despite relatively low sequence divergence among recently diverged species of Western New World lupins, the range of life forms (from dwarf annuals and prostrate herbs to small trees), and habitats occupied is striking. This accelerated morphological and ecological diversification suggests that many genes may have been under strong adaptive selection. The aim of the project is to address currently unanswered questions about the types of genes involved in adaptation during adaptive radiations as well as the relative roles of selection at the amino acid level versus regulatory regions. This will involve the comparisons of the patterns of DNA sequence divergence and gene expression between closely related and recently diverged species with divergent life forms and adapted to a range of environments. Genome-wide DNA polymorphism/divergence as well as expression data will be obtained by Solexa/Illumina sequencing of cDNA. This will be done for actively radiating clades of species in the Andes and North America as well as for a set of species outside actively radiating clades for comparison.