Do size and age matter? Exploring the origins and drivers of plant diversity on islands

兰科和桃金娘科是加勒比海地区植物区系的两个独特而多样的成分，与西班牙植物一样。最近的研究表明，这两个类群可能起源于大陆新热带生物地理区。特别是，热带安第斯山脉和南美洲东南部是兰科和桃金娘科植物迁徙的重要来源地。加勒比植物区系被认为是一致的就地多样化的混合体，但有南美洲大陆的重要贡献。然而，这些关键加勒比因素的详细宏观演变动态和起源仍然知之甚少。为了解决这种知识差距，需要更多的系统基因组数据来重建具有不同地质历史和当前压力的岛屿系统的进化模式。符合逻辑的研究--用来区分岛屿上特有的假定驱动因素的影响的群体是具有广泛的生态位和高度物种多样性的谱系，如兰科和桃金娘科。该项目的总体目标是利用高通量测序数据集为兰科和桃金娘科建立强大和采样良好的系统基因组框架，从而能够在时间和空间上追踪伊斯帕尼奥拉这两个类群的起源和多样性。具体地说，我们提出以下问题：a)这些群体物种多样性的来源在哪里？B)地理隔离和与其他岛屿或大陆系统的生物交换如何影响岛屿特有？C)岛屿大小和年龄如何影响岛屿植物区系演化的模式和节奏？这项研究将检验以下假设：H1：在伊斯帕尼奥拉岛上发现的大多数特有物种是预先适应的候鸟就地多样化的结果。H2：岛屿年龄和大小的差异与岛屿系统中物种特有的水平相关不显著。H3：山脉形成和/或气候或地质变量的变化导致的生态位异质性对伊斯帕尼奥拉兰科和桃金娘科物种多样性的影响比这些生态位演变的速度更大。将在伊斯帕尼奥拉进行实地工作，收集兰科和桃金娘科组织样本，以提取DNA。然后，研究小组的超级树将使用现场收集的样本和来自标本馆的DNA和现有的DNA序列数据进行补充。将对由此产生的树木推论进行比较系统发育分析，如祖传面积和多样化比率估计。兰科和桃金娘科祖先的气候生态位将根据生物气候变量进行估计。这种分析与多样化比率分析相结合，将能够比较谱系多样化和灭绝与伊斯帕尼奥拉气候生态位变化率之间的关系，并将能够在岛屿植物区系演变的背景下重建和审查具有不同生活史的物种丰富群体的演变。

Orchidaceae and Myrtaceae are two characteristic and diverse floristic elements of the Caribbean region in general, as well as Hispaniol. Recent studies indicate that both groups might have originated in continental Neotropical biogeographical regions. In particular, the Tropical Andes and southeastern South America were an important source area of migrants for Orchidaceae and Myrtaceae. The Caribbean flora is thought to be derived from a mix of consistent in-situ diversification but with important contributions from mainland South America. However, the detailed macro-evolutionary dynamics and origins of these key Caribbean elements are still poorly understood. To address such knowledge gaps, more phylogenomic data is required to reconstruct evolutionary patterns in island systems with different geological histories and current pressures. Logical study-groups with which to disentangle influences of putative drivers of endemism on islands are lineages with wide ecological niches and high species diversity, such as Orchidaceae and Myrtaceae. The overarching aims of this project are to generate robust and well sampled phylogenomic frameworks for the Orchidaceae and Myrtaceae using highthroughput sequencing datasets that can enable the tracing in time and space the origin and diversification of these two groups in Hispaniola. Specifically, we ask the following questions: A) where is the source of species diversity in these groups? B) How does geological isolation vs biological exchange with other island or continental systems influence island endemism? C) How does island size and age influence the mode and tempo of island flora evolution? The study will test the following hypotheses: H1: Most endemic species found on the island of Hispaniola are the result of in-situ diversification of pre-adapted migrants. H2: Island age and size differences are not significant relative to levels of species endemism in island systems. H3: Niche heterogeneity resulting from mountain formation and/or variations in climate or geological variables had a greater influence in rates of diversification of Orchidaceae and Myrtaceae in Hispaniola than the pace at which these niches evolved. Fieldwork in Hispaniola will be undertaken to collect Orchidaceae and Myrtaceae tissue samples for DNA extraction. Dated super-trees of the study groups will be then produced using field-collected samples supplemented with DNA from herbarium specimens and existing DNA sequence data. Comparative phylogenetic analyses such as ancestral area and diversification rate estimation will be conducted on resulting tree inferences. Ancestral climatic niches of Orchidaceae and Myrtaceae will be estimated from bioclimatic variables. Such analyses coupled with diversification rates analysis will allow comparison of lineages diversification and extinction vs rate of climatic niches change in Hispaniola and will allow the evolution of species-rich groups with differing life histories to be reconstructed and examined in the context of the evolution of an island flora.