Explaining the biological diversity in tropical America: a phylogenetic and biogeographic approach

热带美洲拥有世界约37%的物种，是地球上物种最丰富的地区。了解这种多样性的历史对物种保护具有重要意义。我的长期研究计划旨在解释与热带美洲地理相关的历史事件如何影响这种高度物种多样性的进化和分布。我将使用陆地植物来解决三个短期目标。 首先，我将使用大约10个基因的DNA来创建棕榈族Eurpeae的系统发育树。这棵树将允许重建潜在的地理区域和栖息地类型，这一群体的祖先最初生长在那里。这次重建将检验许多科学假说。例如，白沙作为热带美洲植物祖先栖息地的作用将被阐明。两名硕士研究生将在实验室本科生的帮助下开发这一目标。棕榈树等重要经济植物及其野生近缘植物的系统发育树不仅对植物分类很重要，而且对作物和园艺科学家来说也很重要，因为它们提供了一个进化框架来发现重要的农艺性状。 对于我的第二个短期目标，我将推断加勒比海岛屿和美洲大陆之间不同血统的起源和迁徙的时间。我将使用在网络上至少有75%的系统发育信息的植物群来扩展我以前研究的样本。通过综合这些信息，将检验几个假设，例如，大陆桥是否促进了大约3400万年前从大陆到大安的列斯群岛的植物迁徙。一名博士生将领导这项工作，本科生将帮助收集有关植物分布、DNA序列和校准系统发育树所需的化石的信息。这一目标不仅将推动生物地理学领域的发展，而且将促进热带生态系统的保护。通过考虑导致当前物种分布格局的当地和迁徙事件，全面了解过去的生物交换将有助于保护和恢复地区的设计。 我的第三个短期目标是寻找姐妹种群在物种形成过程中最常见的地理分布模式的证据。种群可以变成不同的物种，即使在同一地区并排生长并在最初阶段交换基因(同域物种形成)。同域物种形成的另一种情况是，种群之间没有接触，因为它们通常被地理屏障隔开，因此它们之间没有基因流动(异地物种形成)。我们将通过分析姐妹物种的地理重叠及其与系统发育距离的关系来揭示这些物种形成机制在热带美洲出现的相对频率。由本科生资助的第二名博士生将在公共数据库中进行这一客观搜索，以寻找具有几乎完整的系统发育树(90%的信息)的植物类群。这一目标的结果将引起进化生物学家的兴趣，因为当前物种的空间和遗传背景可以提供对导致物种形成的过程的性质和强度的洞察。 了解影响热带物种起源和分布的地理和遗传因素对于解释加拿大物种分布也很重要，因为它们都有全球气候和生物地球化学循环。

Harboring approximately 37% of the world’s species, tropical America is the most species rich region on earth. Understanding the history of such diversity has important implications for species conservation. My long-term research program aims to explain how historical events related to the geography of tropical America have influenced the evolution and distribution of this high species diversity. I will use land plants to address three short-term objectives. First, I will use DNA from approximately 10 genes to create a phylogenetic tree of the palm group Euterpeae. This tree will permit a reconstruction of the potential geographic regions and habitat types where the ancestors of this group first grew. This reconstruction will test numerous scientific hypotheses. For example, the role of white sands as the ancestral habitat of tropical American plants will be elucidated. Two Msc students will develop this objective aided by undergraduate students in the laboratory. Phylogenetic trees of economically important plants such as palms, and their wild relatives, are important not only for plant classification, but also for crop and horticultural scientists by providing an evolutionary framework to discover important agronomic characteristics. For my second short-term objective, I will infer the timing of origin and migration of different lineages among the Caribbean islands and the American continent. I will use plant groups for which there is at least 75% phylogenetic information publicly available on the web to extend the sampling from my previous studies. By synthesizing this information, several hypotheses will be tested, for example whether a land bridge facilitated the immigration of plants from the continent to the Greater Antilles, approximately 34 million of years ago. A PhD student will lead this work, and undergraduate students will help to collect information on plant distributions, DNA sequences, and fossils necessary to calibrate the phylogenetic trees. This objective will not only advance the field of biogeography but also the conservation of tropical ecosystems. A comprehensive understanding of past biotic interchange will aid the design of protected and restored areas by considering the local and migration events that led to the current species distribution patterns. My third short-term objective is to look for evidence of the most common geographic distribution pattern of sister populations undergoing the process of speciation. Populations can become different species even if growing side by side on the same region and exchanging genes during the initial stages (sympatric speciation). An alternative scenario to sympatric speciation is the one in which populations do not have contact because they are separated usually by a geographic barrier, and thus no gene flow occurs between them (allopatric speciation). We will reveal the relative frequency in which these speciation mechanisms occur in tropical America by analyzing the geographic overlap of sister species and its relationship with phylogenetic distance. A second PhD student aided by undergraduates will conduct this objective searching in public databases for plant groups for which there is an almost complete phylogenetic tree (90% information). The outcomes of this objective will be of interest to evolutionary biologists because the spatial and genetic context of current species can provide insight into the nature and strength of the processes leading to speciation. An understanding of the geographical and genetic factors affecting species origins and distribution in the tropics is also important to explain Canadian species distribution because they all share global climatic and biogeochemical cycles.