THE GENETIC BASIS OF LOCAL ADAPTATION ACROSS AN ISLAND ADAPTIVE RADIATION

许多物种起源于被称为适应性辐射的剧烈爆发。适应性辐射如何在短时间内产生数量惊人的物种是进化生物学的一个基本问题。偏远岛屿上的适应性辐射尤其令人着迷，因为这种辐射来自具有有限遗传变异的创始种群，而遗传变异是进化的原材料。了解偏远岛屿适应性辐射的遗传基础，不仅可以深入了解物种的起源（以及生物多样性），还可以了解物种如何应对快速的气候变化。该项目将揭示Metrosideros对极端水可用性（干旱和洪水）的适应遗传基础，这是夏威夷森林中主要的木本物种的适应性辐射。结果将揭示对非常潮湿和非常干燥环境的反复适应依赖于创始种群中存在的古老基因的再循环，而不是通过突变产生的新基因。通过古老基因的循环循环进行的反复适应将有助于解释适应性辐射是如何发生的，并表明物种能够适应快速的气候变化。特别是，该项目将揭示树木如何应对气候变化带来的日益严重的干旱和洪水。该项目还将在尖端技术和分析方面培训一名技术员、两名博士生和几名本科生，为两所少数民族服务机构的联邦和州机构工作人员、学生、教师和工作人员提供生物信息学培训，并开发与植物适应和应对气候变化相关的G6-12课程。拟议的研究将采用进化系统生物学方法对夏威夷的景观优势木本属Metrosideros进行研究，以表征整个岛屿适应水可用性的遗传基础。该项目将利用相对较小的基因组大小和高质量的染色体水平参考基因组；亲本系、F1系和F2系；和人口水平的重测序数据，为Metrosideros实现3个目标：目标1)比较重复的干适应和湿适应类群对干旱和涝渍的幼苗生理和基因表达模式；目标2)鉴定抗旱或涝渍的表型性状和数量性状位点（QTL），并鉴定与差异表达基因（DEGs）共定位的QTL；目标3)研究共定位的DEG-QTL区域(和非相交的，夏威夷Metrosideros适应性辐射中的显著QTL)，以验证对平行环境的反复适应涉及对主要祖先起源的共享基因组区域的反复选择的预测。通过研究岛屿适应性辐射的局部适应的遗传基础，该项目将有助于解决长期存在的进化问题，即如何从遗传变异有限的创始种群中产生惊人的表型和生态多样性。具体来说，研究结果将揭示对平行环境的反复适应在多大程度上利用了不同分类群中相同的基因组区域，以及共同祖先变异、基因渗入和新生突变对孤立辐射内平行进化的相对重要性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Many species originate in dramatic bursts called adaptive radiations. How adaptive radiations generate spectacular numbers of species over short time periods is a fundamental question in evolutionary biology. Adaptive radiations in remote islands are especially fascinating, given that such radiations originate from founder populations with limited genetic variation, which is the raw material for evolution. Understanding the genetic basis of adaptive radiations on remote islands allows insight into not only the origin of species (and, hence, biodiversity), but also how species will respond to rapid climate change. This project will uncover the genetic basis of adaptation to extreme water availability (drought and flooding) in Metrosideros, an adaptive radiation of woody species that dominate Hawaii’s forests. The results will reveal how often recurring adaptation to very wet and very dry environments relies on the recycling of ancient genes present in the founder population versus new genes arising through mutation. Repeated adaptation through the recycling of ancient genes would help to explain how adaptive radiations occur and would suggest that species are able to adapt to rapid climate change. In particular, this project will reveal insights into how trees will cope with the increased drought and flooding expected with climate change. The project will also train one technician, 2 Ph.D. students, and several undergraduates in cutting-edge technologies and analyses, provide bioinformatics training to federal and state agency staff and students, faculty, and staff at two Minority-Serving Institutions, and develop G6-12 curriculum related to plant adaptation and response to climate change.The proposed research will apply an evolutionary systems biology approach to Hawaii’s landscape-dominant woody genus, Metrosideros, to characterize the genetic basis of local adaptation to water availability across an island adaptive radiation. The project will take advantage of the relatively small genome size and high-quality chromosome-level reference genome; parental, F1, and F2 lines; and population-level resequencing data available for Metrosideros to accomplish 3 aims: Aim 1) contrast seedling physiology and patterns of gene expression between replicate dry- and wet-adapted taxa in response to drought and water-logging, Aim 2) identify phenotypic traits and quantitative trait loci (QTL) for resistance to drought or water-logging and identify QTL that colocalize with differentially expressed genes (DEGs), and Aim 3) examine the evolution of the colocalized DEG-QTL regions (and non-intersecting, but significant QTL) across the Hawaiian Metrosideros adaptive radiation to test the prediction that recurring adaptation to parallel environments involves recurring selection on shared genomic regions of predominantly ancestral origin. By investigating the genetic basis of local adaptation across an island adaptive radiation, this project will help to solve the long-standing evolutionary problem of how spectacular phenotypic and ecological diversity can arise from founder populations with limited genetic variation. Specifically, results will reveal the degree to which recurring adaptation to parallel environments draws on the same genomic regions in different taxa and the relative importance of shared ancestral variation, introgression, and de novo mutations for parallel evolution within an isolated radiation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.