Collaborative Research: Genetic diversity, resistance genes, and negative density dependence in tropical tree seedling dynamics

热带森林以其高度的生物多样性而闻名，这在一定程度上是因为它们含有大量稀有物种。热带树木稀有的一个原因似乎是在同一物种的个体之间传播的疾病的高死亡率。当一个稀有物种的幼苗被同一物种的邻居包围时，其死于病原体的风险比被该物种的邻居包围的普通物种的幼苗高得多。这个项目将测试新的假设，即稀有与低抵抗力是相伴的，因为一个物种只有少量的个体会导致负责抗病的基因的多样性也很低。这一假说将通过史密森学会和宾夕法尼亚州立大学的科学家合作进行验证。巴拿马史密森热带研究所将从相关的稀有和常见热带树种中收集植物组织。这些组织将被运往宾夕法尼亚州，在那里，一种名为下一代转录组测序的分子遗传学新技术将被用来量化每个物种的总体和抗性基因多样性。回到巴拿马，森林中的实验将测试加强树木之间的异花授粉是否可以增加它们后代的基因多样性，使它们对疾病有更大的抵抗力和生存机会。这项研究将为物种丰富如何塑造其抵御疾病的能力提供有用的见解。了解这一点将有助于我们理解为什么一些物种稀有，而另一些物种很常见，并帮助森林管理者做出更明智的决定。该项目将首次从树木中获得大量的抗性基因序列，这些信息可用于未来农业和园艺植物遗传多样性的研究。该项目还将为美国和巴拿马的学生和早期职业生物学家提供培训。

Tropical forests are known for their high biological diversity, and this is partly due to the large numbers of rare species they contain. One reason for rarity in tropical trees seems to be high rates of death from diseases that spread between individuals of the same species. When a seedling of a rare species is surrounded by neighbors of the same species, its risk of dying from pathogens is much higher than that of a seedling of a common species surrounded by neighbors of that species. This project will test the new hypothesis that rarity goes along with low resistance to disease because having just a small number of individuals of a species leads to also having a low diversity of the genes that are responsible for disease resistance. The hypothesis will be tested through collaboration between scientists at the Smithsonian Institution and Pennsylvania State University. Plant tissue will be collected from related pairs of rare and common species of tropical trees at the Smithsonian's Tropical Research Institute in Panama. The tissue will be shipped to Pennsylvania, where a new technique in molecular genetics known as next generation transcriptome sequencing will be used to quantify the overall and resistance gene diversity of each species. Back in Panama, experiments in the forest will test whether enhancing cross-pollination between trees can increase the genetic diversity of their offspring and give them greater resistance to disease and chances of survival.This study will provide useful insights into how the abundance of a species can shape its ability to resist disease. Knowing this will help us understand why some species are rare while others are common, and help forest managers make more informed decisions. This project will be the first to obtain a large collection of resistance gene sequences from trees, information that can used in future studies of genetic diversity in agricultural and horticultural plants. The project will also provide training for students and early career biologists in both the United States and Panama.