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地区和伊斯帕尼奥岛的两个特色和多样化的植物区系。最近的研究表明，这两个群体可能起源于大陆新热带生物地理区域。热带安第斯山脉和南美洲东南部是兰科和桃金娘科重要的迁徙源区。加勒比地区的植物群被认为是由一致的原位多样化混合而来，但南美洲大陆也有重要贡献。然而，这些加勒比关键因素的详细宏观演化动态和起源仍然知之甚少。为了解决这些知识空白，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。合理的研究群体是具有广泛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使用高通量测序数据集为兰科和桃金桃科生成可靠且采样良好的系统基因组框架，从而可以在时间和空间上追踪伊斯帕尼奥拉岛这两个群体的起源和多样化。具体来说，我们提出了以下问题：A)这些群体中物种多样性的来源在哪里？B)地质隔离与与其他岛屿或大陆系统的生物交换如何影响岛屿特有性？C)岛屿的大小和年龄如何影响岛屿植物群进化的模式和速度？本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适应移民的原位多样化的结果。H2：相对于岛屿系统中物种特有的水平，岛屿年龄和大小的差异并不显著。H3：山的形成和/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岛兰科和桃金娘科多样性的影响大于这些生态位进化的速度。将在伊斯帕尼奥拉岛进行实地调查，收集兰科和桃金娘科组织样本进行DNA提取。然后将使用现场收集的样本，补充植物标本馆标本的DNA和现有DNA序列数据，制作研究组的过时超级树。比较系统发育分析，如祖先区域和多样化率估计，将在由此产生的树推断上进行。利用生物气候变量估计兰科和桃金娘科祖先的气候生态位。这样的分析与多样化率分析相结合，可以将伊斯帕尼奥拉岛的谱系多样化和灭绝与气候生态位变化的速度进行比较，并可以在岛屿植物群进化的背景下重建和检查具有不同生活史的物种丰富群体的进化。

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.