DISSERTATION RESEARCH: Investigating the main contributors to plant speciation in a rapidly diverging lineage in western North America

对物种形成过程的研究，或一个物种分裂为两个物种的过程，大多采取了对单个物种或物种对进行深入研究的方法，因此侧重于这一事件分歧的主要驱动因素。相反，如果我们对物种形成采取更长期的进化观，通过进化关系和对识别和定义物种很重要的特征的镜头进行检查，我们就有机会在最近物种形成事件的水平上以及通过该群体的进化史来研究物种属性的相对贡献。这意味着我们可以自信地识别和描述物种。分子、形态、生态和/或地理变异通常是一个物种和另一个物种之间界限的证据，然而，当单独使用时，这些特征并不总是能够区分物种。这项研究将对物种划分理论和方法的实证检验做出重大贡献，并将弥合理论、经验和应用科学之间的差距。通过努力定义反映物种进化史的物种，该项目将有助于发现、保护和管理北美西部的生物多样性。最后，本研究将通过学习新的实验室、现场和分析技术，以及对本科生的指导和培训，直接影响联合PI的培训和学术发展。该项目旨在通过确定物种标准、严格界定物种以及评估单个物种标准在整个系统发展史中的作用，确定物种形成的宏观进化特征，以开始构建北美西部山区物种形成的总体图景。为了实现这一目标，该项目需要1)收集广泛的物种标准数据(即分子、形态、生态、地理和细胞学数据)，2)应用严格的物种划分方法(使用多个个体标准和综合数据方法)，重点放在全属系统发育中分辨不佳的节点上，以及3)通过对特征随时间进化的速度的比较系统发育分析来检查个别物种标准的相对贡献。北美西部的几个物种复合体来自不同的多年生画笔支系(卡斯蒂利亚属、奥罗班科)，是解决这些问题的模式系统，并因其在形态、生态和细胞学特征上的对比差异而被选中。

Studies of the process of speciation, or the splitting of one species into two, have most often taken the approach of intensive study of a single species or species pair, and have therefore focused on the primary driver of divergence of that one event. If instead, we take a longer-time, evolutionary view of speciation, examined through the lens of evolutionary relationships and the traits that are important for recognizing and defining species, we have the opportunity to investigate the relative contributions of the properties of a species at both the level of recent speciation events and back through the evolutionary history of the group. This implies that we can confidently identify and describe species. Molecular, morphological, ecological, and/or geographic variation often serve as evidence of boundaries between one species and another, however, when used alone, these characteristics are not always capable of differentiating species. This study will contribute significantly to empirical tests of the theory and methodologies of species delimitation, and will bridge the gap between theoretical, empirical, and applied sciences. By working towards definitions of species that reflect their evolutionary histories, this project will contribute to the discovery, conservation, and management of biodiversity in western North America. Finally, this research will directly impact the training and academic development of the co-PI through the learning of new laboratory, field, and analytical techniques, as well as the mentoring and training of undergraduates. This project aims to identify the macroevolutionary signatures of speciation via the identification of species criteria, the robust delimitation of species, and the evaluation of the contribution of individual species criteria across a phylogeny, to begin to construct a broad picture of speciation in the mountains of western North America. To accomplish this objective, this project entails 1) the collection of extensive species criterion data (i.e., molecular, morphological, ecological, geographic, and cytological data, 2) the application of rigorous species delimitation methods (using multiple individual criteria and an integrated data approach) focused on poorly resolved nodes in a genus-wide phylogeny, and 3) the examination of the relative contributions of individual species criteria through comparative phylogenetic analyses of the rate of trait evolution through time. Several western North American species complexes from the diverse perennial clade of the paintbrushes (Castilleja, Orobanchaceae) are the model system for approaching these questions, and were selected for their contrasting variation in morphological, ecological, and cytological characteristics.