DISSERTATION RESEARCH: A next-generation sequencing framework for understanding trait evolution across multiple scales in the Viburnum lentago clade

许多植物品种变异极大。 即使在一个种群中，同一物种的植物也可以在叶形或花色等特征上彼此不同。然而，几乎所有关于性状进化的大规模研究都忽略了物种内部的这种变化，而是为每个物种分配一个单一的值。部分原因是，我们对物种内部的变异如何与更长时间尺度上的进化分化相关知之甚少。该项目的重点是六个密切相关的灌木物种，原产于美国东部。目标是量化物种内不同类型的变异，并将观察到的模式与这些物种在过去500万至2000万年间的进化方式联系起来。特别强调将放在描述一组叶特征（大小，形状，叶缘）的变化，在个别植物，种群内，跨种群跨越纬度梯度的生长条件，跨物种。这些数据将有助于更好地预测哪些性状最有可能进化，以及植物物种如何应对未来的气候变化。 该项目使用新的下一代分子方法来生成开花植物进化枝荚属内Lentago谱系的系统发育和地理分布数据。RAD（限制性位点相关DNA）标记将对每个物种30多个个体进行测序，以创建跨越分歧水平的高分辨率同源性，将仅在几百年前分歧的种群与中新世的物种形成事件联系起来。这个系统发育框架将解决物种关系，确定分支内杂交的程度，并使研究人员能够重建每个物种的地理（种群水平）历史。由此产生的共同祖先和迁移历史的详细了解将提供新的见解适应和基因流如何产生和维持物种内和物种间的性状变异。该项目将提高对形态特征变异起源的理解，变异类型如何在组织层次之间转换，以及标志着生命之树更深分支的特征的出现。

Many plant species are extremely variable. Even within a population, plants of the same species can differ from one another in characteristics such as leaf shape or flower color. However, almost all broad-scale studies of trait evolution ignore such variation within species and instead assign a single value to each species. Partially for this we know little about how variation within species relates to evolutionary differentiation over longer timescales. This project focuses on six closely related species of shrubs that are native to the Eastern United States. The goal is to quantify different types of variation within species and to relate the observed patterns to how these species evolved over the past 5-20 million years. Special emphasis will be placed on describing variation in a set of leaf characteristics (size, shape, leaf margins) within individual plants, within populations, across populations spanning a latitudinal gradient in growing conditions, and across species. These data will allow a better prediction of which traits are most likely to evolve and how plant species might respond to future climate change. This project uses a new next-generation molecular method to generate phylogenetic and phylogeographic data for the Lentago lineage within the flowering plant clade Viburnum. RAD (Restriction site Associated DNA) markers will be sequenced for over 30 individuals per species to create a high-resolution phylogeny that spans across levels of divergence, linking populations that diverged only several hundred years ago to speciation events in the Miocene. This phylogenetic framework will resolve species relationships, determine the extent of hybridization within the clade, and enable the researchers to reconstruct the phylogeographic (population-level) history of each species. The resulting detailed understanding of common ancestry and migration history will provide new insight into how adaptation and gene flow generate and maintain trait variation within and among species. The project will improve understanding of the genesis of variation in morphological traits, of how types of variation translate across levels of organization, and of the emergence of the traits that mark deeper branches in the tree of life.