Symbiotic ecology: mycobiont-photobiont interactions in tropical lichens along environmental gradients

地衣共生是真菌（真菌）和光生菌（绿藻和/或蓝藻）之间的共生关系，其中光生菌提供碳水化合物，真菌为其光生菌提供庇护环境。在其复杂的进化史中，这种非常成功的营养策略已经演变成大量不同的生长形式和栖息地生态，地衣几乎可以在从热带到极地的所有陆地生态系统中找到。分子生物学方法的应用揭示了以前意想不到的遗传多样性水平，特别是在许多热带地衣-共生生物谱系中，虽然北方和温带地区的一些大地衣群体相对已知，但关于热带地区的共生多样性和关联模式的知识很少。然而，了解多样性模式和物种相互作用的生态学的相关性是解决环境变化对地衣的挑战的基础。这个项目的目的是探索共生多样性和相互作用的复杂性如何与环境变量相关，并定义共生生态学。该方案的重点是在热带乞力马扎罗山陡峭的山坡上，地衣共生体的相互作用。该研究环境以前由DFG资助的乞力马扎罗山研究小组建立，包括60个具有已知环境条件的永久性研究地块，代表从热带稀树草原到高山荒原植被的12种不同生态系统。采用分子生物学方法对地衣菌体和基质样品的地衣共生体多样性进行了分析。物种假设是使用DNA条形码方法构建的。采用非参数乘法回归（NPMR）分析了共生群落和关联模式之间的差异及其与环境变量的相关性。利用既定的研究设计，独特的生物材料，最先进的分子方法，和彻底的数据分析，我可以回答一些相关的和及时的研究问题和测试预测。我的具体目标包括以下几点。A)环境胁迫对单个共生体基因型和共生体群落（地衣物种）的影响。B)共生相互作用在决定生境和底物生态中的作用。C)光生物介导的地衣公会的预测促进作用和公会水平的相互作用如何影响地衣群落结构。该项目将极大地提高我们目前对地衣生态学和生物地理学的认识，特别是对地衣共生中真菌-光生物和真菌-真菌相互作用的认识，并代表着热带地衣学的一个新的开端。

Lichen symbioses are mutualistic associations between mycobionts (fungi) and photobionts (green algae and/or cyanobacteria) in which the photobionts provide carbohydrates and the fungi provide a sheltered environment for their photobionts. During their complex evolutionary history, this highly successful nutritional strategy has evolved to a plethora of different growth forms and habitat ecologies, and lichens can be found in almost all terrestrial ecosystems from the tropics to polar regions. The application of molecular biological methods has revealed previously unexpected levels of genetic diversity especially in many tropical lineages of lichen-symbiotic organisms, and while some groups of macrolichens in boreal and temperate regions are relatively well known, the knowledge about symbiont diversity and association patterns in the tropics is meagre. However, understanding the relevance of the diversity patterns and the ecology of species interactions is fundamental in addressing the challenges of environmental change to lichens. It is the aim of this project to explore how the symbiotic diversity and the complexity of interactions relate to environmental variables and define symbiont ecology. The proposal focuses on lichen symbiont interactions along a steep environmental gradient on the slopes of the tropical Mount Kilimanjaro. The study setting, previously established by the DFG funded Kilimanjaro Research group, includes 60 permanent study plots with known environmental conditions, representing 12 different ecosystems from tropical savanna to alpine heath vegetation. Lichen symbiont diversity sampled both from lichen thalli and from substrate samples on the sample plots is analyzed using molecular biological methods. Species hypotheses are constructed using a DNA barcoding approach. Nonparametric multiplicative regression (NPMR) is used to analyze differences between symbiont communities and association patterns and their correlations with environmental variables. Utilizing the established study design with unique biological material, state-of-the-art molecular methods, and thorough data analysis, I can answer several relevant and timely research questions and test predictions. My specific aims include the following. A) What is the impact of environmental stress on individual symbiont genotypes and symbiotic consortia (lichen species). B) What is the role of symbiotic interactions in determining habitat and substrate ecology. C) How does the predicted facilitative role of photobiont-mediated lichen guilds and the guild-level interactions impact lichen community structure. This project will dramatically improve our current understanding of lichen ecology and biogeography, especially mycobiont-photobiont and mycobiont-mycobiont interactions within lichen symbioses, and represent a new opening in tropical lichenology.