DISSERTATION RESEARCH: Phylogeny, reticulate evolution, and historical biogeography in the Hawaiian lobeliad genera Cyanea and Clermontia

适应性辐射是指一组生物体受到辐射以发挥多种生态作用，这为研究使物种在有限的地理区域内迅速多样化的机制提供了机会。产于夏威夷群岛的半边莲属植物在生境、生长形态、叶片大小和形状、花形态和种子传播机制等方面经历了显著的差异，被认为是植物适应性辐射的最好例子之一。之前的研究表明，这140个物种起源于1300万年前的一次殖民活动，远远早于今天的许多夏威夷岛屿从太平洋中出现。夏威夷半边莲现在占夏威夷本土植物区系的12%，是地球上任何一组海洋岛屿上发现的物种最丰富的植物谱系。最大的两个属，蓝藻属和克莱蒙蒂属，由大约100种组成，构成了该类群中最大的亚系。以前对蓝藻-克勒蒙亚的系统发育分析没有定论，这是因为该群内的样本有限，而且DNA序列变异不足以重建得到充分支持的亲缘关系估计。由于其大小、生态和形态多样性以及仅限于单个岛屿的物种比例很高(每个岛屿的年龄都已知)，蓝藻-克莱蒙特群岛为研究适应性辐射、物种形成和历史生物地理学提供了独特的机会。了解这一谱系中的关系可以为夏威夷动植物多样性的上升提供新的见解，并识别与变得稀有或灭绝的趋势有关的特征。该项目将(1)广泛培训植物系统学和历史生物地理学分析方面的研究生；(2)开发分子系统发育分析管道，以帮助研究其他最近的辐射；(3)产生有良好文件记录的DNA样本集合，以便将来对这一重要群体进行研究；(4)创建一个关于夏威夷原生半边莲多样性的网站，向广泛的业余植物学家和半边莲爱好者传播研究结果。下一代DNA测序数据将被用于从全叶绿体基因组和所有范围内采样的所有活物种的400个核基因中推断蓝藻属的系统发育。对这些数据的分析将使物种树和网络的推导、杂交、渐渗和其他形式的网状进化(在克莱蒙特很重要)的分析成为可能，重建其随时间的地理分布，并使用各种基于树和网络的方法推断关键形态和生态特征状态的进化模式和节奏。

Adaptive radiations, where a group of organisms has radiated to perform a number of ecological roles, offer an opportunity to investigate the mechanisms that allow species to diversify rapidly within a limited geographical area. Members of the lobelia plant family (Lobeliaceae) restricted to the Hawaiian Islands have undergone a remarkable divergence in habitat, growth form, leaf size and shape, floral morphology, and mechanism of seed dispersal, and are considered one of the best examples of an adaptive radiation in plants. Previous studies have shown that this group of 140 species was derived from a single colonization 13 million years ago, long before many of the Hawaiian islands of today had emerged from the Pacific. Hawaiian lobeliads now represent 12% of the native Hawaiian flora and are the most species-rich plant lineage found on any single group of oceanic islands on Earth. The two largest genera, Cyanea and Clermontia, comprising approximately 100 species form the largest sublineage within the group. Previous phylogenetic analyses of Cyanea-Clermontia were inconclusive due to a combination of limited sampling within the group and insufficient DNA sequence variation to reconstruct a well-supported estimate of relationships. Cyanea-Clermontia, by its very size, ecological and morphological diversity, and high proportion of species restricted to single islands (each of known age), offers unique opportunities for studying adaptive radiation, speciation, and historical biogeography. Understanding relationships within this lineage could provide new insights into the rise of plant and animal diversity on Hawaii, and identify traits associated with a tendency to become rare or extinct. This project will (1) broadly train a graduate student in plant systematics and historical biogeography analyses; (2) develop molecular phylogenetic analysis pipelines to aid in the study of other recent radiations; (3) produce a well-documented collection of DNA samples to permit future studies of this important group; and (4) create a website on the diversification of native Hawaiian lobeliads, to disseminate findings to a broad range of amateur botanists and lobeliad enthusiasts.Next-generation DNA sequencing data will be used to infer phylogenies of Cyanea-Clermontia from whole-chloroplast genomes and 400 nuclear genes for all living species sampled across their range. Analyses of these data will permit derivation of species trees and networks, analysis of hybridization, introgression, and other forms of reticulate evolution (important in Clermontia), reconstruct its geographic spread through time, and infer the pattern and tempo of evolution of key morphological and ecological character-states using a variety of tree- and network-based approaches.