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，部分原因是它们含有大量的稀有物种。热带树木罕见的一个原因似乎是同一物种个体之间传播的疾病死亡率很高。当一种稀有物种的幼苗被同一物种的邻居包围时，它死于病原体的风险要比一种普通物种的幼苗被该物种的邻居包围的风险高得多。这个项目将测试一个新的假设，即稀有与低抗病能力有关，因为一个物种只有少数个体，导致负责抗病能力的基因多样性也很低。史密森学会（Smithsonian Institution）和宾夕法尼亚州立大学（Pennsylvania State University）的科学家将合作对这一假设进行检验。植物组织将在巴拿马的史密森尼热带研究所从稀有和常见的热带树种中收集。这些组织将被运往宾夕法尼亚州，在那里，一种被称为下一代转录组测序的分子遗传学新技术将被用于量化每个物种的总体和抗性基因多样性。回到巴拿马，在森林中进行的实验将测试增强树木之间的异花授粉是否可以增加其后代的遗传多样性，并使它们具有更强的抗病能力和生存机会。这项研究将提供有用的见解，了解物种的丰度如何影响其抵抗疾病的能力。了解这一点将有助于我们理解为什么有些物种很罕见，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。该项目将是第一个从树木中获得大量抗性基因序列的项目，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.