Collaborative Research: Diversity, Distribution, and Demographic Effects of Seed-Associated Fungi in Neotropical Cecropia

真菌病原体越来越多地被认为是热带森林中成株和幼苗死亡的重要来源，影响树木的人口，分布和多样性。然而，很少有人知道种子感染真菌，影响种子存活的隐藏效果。种子感染真菌可能是特别重要的树种取决于种子存活在土壤中（种子库）的成功招聘。我们将在三个热带森林（哥斯达黎加，巴拿马，厄瓜多尔）进行种子感染真菌（内生菌，腐殖菌，病原体）与焦点种子库依赖的热带树木（Cecropia，荨麻科）的详细生态和分子特征。利用田间试验，我们将评估种子死亡率归因于真菌的12个物种，和本地与外来真菌在种子存活的三个古老的森林物种的作用。我们将使用分子序列数据来鉴定真菌，并重新接种试验来评估种子感染物种的致病性。在这样做时，我们将测试三个主要假设：（i）种子在土壤中的持久性不同树种，反映不同的敏感性真菌感染;（ii）热带种子感染真菌是多样的，并适应当地的主机;（iii）非病原性真菌保护种子免受疾病。该项目有望使人们更深入地了解一组多样和丰富的热带树种的补充的基本因素，这反过来又对森林生态系统的管理和恢复以及热带生物多样性的维持产生重要影响。更广泛的影响包括培训一名博士生在田间生态学和分子技术，改善合作联系在国际一级，和论文支持和培训美国，厄瓜多尔、巴拿马和哥斯达黎加的本科生。我们预计，这项研究将提供在任何自然系统中的种子真菌相互作用的复杂性的第一个见解，并将提供急需的培训，为年轻的研究人员在热带分子生态学。

Fungal pathogens are increasingly recognized as an important source of adult-plant and seedling mortality in tropical forests, influencing tree demography, distributions, and diversity. However, very little is known regarding hidden effects of seed-infecting fungi, which influence seed survival. Seed-infecting fungi are likely to be especially important for tree species depending upon seed survival in soil (seed banks) for successful recruitment. We will undertake a detailed ecological and molecular characterization of seed-infecting fungi (endophytes, saprophytes, pathogens) associated with focal seed-bank-dependent tropical trees (Cecropia, Urticaceae) in three tropical forests (Costa Rica, Panama, Ecuador). Using field experiments, we will assess seed mortality attributable to fungi for 12 species, and the roles of local vs. foreign fungi in seed survival for three old-growth forest species. We will use molecular sequence data to identify fungi, and re-inoculation trials to assess pathogenicity of seed-infecting species. In so doing, we will test three primary hypotheses: (i) seed persistence in soil differs among tree species, reflecting differential susceptibility to fungal infection; (ii) tropical seed-infecting fungi are diverse and adapted to local hosts; (iii) nonpathogenic fungi protect seeds against disease. This project promises a deeper understanding of factors underlying recruitment by a diverse and abundant group of tropical tree species, which in turn has important implications for management and restoration of forest ecosystems and maintenance of tropical biodiversity. Broader impacts include training for a doctoral student in field ecology and molecular techniques, improved collaborative links at an international level, and dissertation support and training for U.S., Ecuadorian, Panamanian and Costa Rican undergraduate students. We anticipate that this study will provide the first insights to the complexity of seed-fungal interactions in any natural system, and will provide much-needed training for young researchers in tropical molecular ecology.