DISSERTATION RESEARCH: The influence of landscape heterogeneity and mycorrhizal fungi on the distribution of an epiphytic orchid and its genetic variation

森林砍伐不仅会减少森林的数量，还会将剩下的森林分成几小块孤立的小块，物种可能无法到达，或者物种一旦到达那里就无法生存，从而威胁到热带地区的生物多样性。附生植物是生活在其他植物之上而不是地面上的植物，是许多物种丰富的热带森林生物多样性的主要组成部分，其中许多附生植物是兰花。兰花有微小的种子，风可以远距离移动，因此它们可能能够从一片森林传播到另一片森林。然而，如果没有专门的真菌，这些微小的种子就不能生长，这种真菌被称为菌根真菌，为兰花提供营养。如果真菌从森林斑块中消失，兰花一旦到达那里就不会存活。这项研究将测试是种子的扩散还是没有真菌的存在，阻止了兰花在热带森林砍伐的地块中生长。工作的重点将是淫羊藿兰花，这是一种在哥斯达黎加大量使用的中等海拔森林中发现的兰花，并结合使用美国的分子遗传学和哥斯达黎加的田间实验。由于热带附生植物是全球受威胁最严重的物种之一，因此这项研究对保护自然资源具有实用价值。这项工作应该为人们提供有价值的见解，了解将热带森林分成更小的斑块如何以特殊方式影响生长在热带树木上的许多兰花，无论是通过导致种子不足还是通过扰乱兰花赖以生存的特殊生态关系。研究结果应有助于指导保护和恢复热带森林物种多样性的努力。此外，该项目还将培养热带野外研究和分子生物学方面的研究生和本科生，并加强国际科学合作。

Deforestation threatens biodiversity in the tropics, not only by reducing the amount of forest, but also by dividing the forest that remains into small, isolated patches that species may not be able to reach or where species may not be able to survive once they get there. Epiphytes, plants that live atop other plants instead of on the ground, are a major part of the biodiversity in many species-rich tropical forests, and many of these epiphytes are orchids. Orchids have tiny seeds that wind can move over long distances, so they might be able to travel from one patch of forest to another. However, the tiny seeds cannot grow without the aid of specialized fungi,known as mycorrhizal fungi,that provide the orchids with nutrients. If the fungi are missing from a forest patch, the orchids will not survive once they get there. This research will test whether it is the dispersal of the seeds or the absence of the fungi that keeps orchids from growing in patches cut from tropical forest. Work will focus on Epidendrum firmum, an orchid found in the heavily used, mid-elevation forests of Costa Rica, and use a combination of molecular genetics in the U.S. and field experiments in Costa Rica. Because tropical epiphytes are among the most globally threatened groups of species, this research has practical value for conservation of natural resources. The work should provide valuable insights into the special ways in which dividing tropical forests into smaller patches can affect the many orchids that grow on tropical trees, whether by causing seeds to fall short or by disrupting the special ecological relationships upon which the orchids depend. The results should help guide efforts to conserve and restore the diversity of species in tropical forests. Furthermore, the project will train graduate and undergraduate students in tropical field research and molecular biology, and strengthen international scientific collaboration.