Biogeography and evolution of the largest adaptive radiation of woody plants (Melicope, Rutaceae) on the Hawaiian Islands

拟议的项目旨在解开夏威夷蜜蜂属（芸香科）的进化历史。夏威夷群岛相对年轻（约500万年），是地球上最孤立的陆地之一。因此，这些岛屿是测试地理学和进化问题的完美天然实验室。蜜瓣花属植物在岛上经历了一次大规模的适应性辐射，产生了52种。蜜蜂花属植物是夏威夷群岛上物种最丰富的植物谱系之一，也是木本植物中辐射最大的。尽管有大量的物种具有相当大的形态变异，夏威夷蜜蜂谱系显示物种之间的遗传变异非常低。六个核和质体标记的桑格测序没有提供足够的可变位点来解决物种水平上的系统发育关系。下一代测序（NGS）方法的引入导致了进化生物学的巨大进步，因为序列数据的质量和数量都有了很大的提高。在拟议的项目中，我们将使用NGS方法限制性位点相关DNA测序（RADseq）。RADseq特别适用于非模式生物，并且已证明其适用于解决物种水平及以下的系统发育关系。拟议的研究的第一个目标-一个解决的物种水平的进化-是进一步研究问题的基础：生物地理分析将提供洞察血统的年龄，夏威夷群岛的殖民化时间，殖民模式的个别岛屿，以及夏威夷蜜蛛的一些物种组是否显示出比其他物种组更高的净多样化率的问题。进一步，我们将测试杂交和多倍化是否在目前物种丰富度的形成中发挥了作用。在提交本提案时，还没有基于夏威夷植物的RADseq研究发表，因此拟议的研究将作为夏威夷植物地理学的案例研究。

The proposed project aims at unravelling the evolutionary history of the Hawaiian Melicope lineage (Rutaceae). The Hawaiian Islands are relatively young (approximately 5 million years) and they rank among the most isolated landmasses on the planet. Therefore the islands are a perfect natural laboratory to test biogeographic and evolutionary questions. The genus Melicope underwent a massive adaptive radiation on the islands, which resulted in 52 species. Melicope is one of the most species-rich plant lineages on the Hawaiian Islands, and it accounts for the largest radiation of woody plants. Despite the high number of species with considerable morphological variation, the Hawaiian Melicope lineage shows very low genetic variation between species. Sanger sequencing of six nuclear and plastid markers did not deliver enough variable sites to resolve phylogenetic relationships at species level. The introduction of next generation sequencing (NGS) methods led to enormous advances in evolutionary biology because of the largely improved quality and quantity of sequence data. Within the proposed project, we will use the NGS method restriction site associated DNA sequencing (RADseq). RADseq is especially suited for non-model organisms and it has proven its suitability to resolve phylogenetic relationships at and below species-level. The first goal of the proposed study - a resolved species-level phylogeny - is the basis for the further research questions: Biogeographic analyses will deliver insight into the age of the lineage, the time of colonization of the Hawaiian Islands, the colonization-pattern of the individual islands, and the question as to whether some species-groups of Hawaiian Melicope show higher net diversification rates than other species-groups. Further on, we will test if hybridization and polyploidization have played a role in the formation of the current species-richness. At the time of submitting this proposal, no RADseq study based on Hawaiian plants has been published, so that the proposed study will serve as a case study in Hawaiian biogeography.