The Role of Fungi in a Lower Devonian Ecosystem

9815669泰勒尽管真菌在世界范围内的多样性和它们在生态相互作用中的重要性，但通过化石记录对它们的多样性知之甚少，几乎没有关于它们在进化过程中的相互作用。然而，苏格兰著名的Rhynie Chert提供了一个了解真菌进化和相互作用的独特窗口，其对植物和动物遗骸的特殊保护，包括相关微生物和真菌生物的细胞细节。这些砂岩沉积物的年代可以追溯到泥盆纪。4亿年前，并记录了一些已知的最早的陆地植物和动物。堪萨斯大学的托马斯·泰勒博士和他的同事们一直在扩大我们对这些沉积物中保存的淡水环境的了解，他们对与许多这些植物和动物有关的各种真菌进行了细致的分析和描述。由于真菌是异养生物，它们需要与其他生物体进行营养相互作用以获得碳源。存在于Rhynie燧石生态系统中的真菌与几组生物（蓝细菌、真细菌、藻类、大型植物）以及其他真菌参与了各种寄生、寄生和互惠关系。例如，一些协会涉及植物根内真菌的形式;和这些植物中的一些拥有自由生活的配子体，也似乎窝藏互惠相关的真菌。在这个下泥盆世的生态系统中，至少还有一种地衣，由蓝细菌和真菌组成。迄今为止，Rhynie燧石中存在的主要真菌群似乎是壶菌和放线菌。记录各种真菌分类群的发生及其相互作用提供了一个独特的机会，可以将这些关联置于进化背景中，测试有关此类相互作用首次出现的假设，并将这些关联与当今已知存在的关联进行比较。

9815669Taylor Despite the worldwide diversity of fungi and their importance in ecological interactions, little is known about their diversity through the fossil record and almost nothing about their interactions through evolutionary time. A unique window into fungal evolution and interaction is provided, however, by the famous Rhynie Chert in Scotland, with its exceptional preservation of plant and animal remains including cellular details of associated microbial and fungal organisms. The sandstone deposits are dated to Devonian times, ca. 400 million years ago, and record some of the earliest known land plants and animals. Dr. Thomas Taylor at the University of Kansas and his colleagues have been expanding our knowledge of the freshwater environment preserved in these deposits, with a program of meticulous analysis and description of the broad range of fungi found in association with many of these plants and animals. Because fungi are heterotrophs, they require a nutritional interaction with other organisms to obtain a source of carbon. The fungi that existed in the Rhynie Chert ecosystem were involved in a variety of saprophytic, parasitic, and mutualistic associations with several groups of organisms (cyanobacteria, eubacteria, algae, macroplants) as well as other fungi. For example, some of the associations involve plant roots in the form of endomycorrhizae; and some of these plants possessed free-living gametophytes that also appear to harbor mutualistically associated fungi. Also present in this Lower Devonian ecosystem was at least one lichen that consisted of colonies of cyanobacteria with the fungus. To date, the major fungal groups present in the Rhynie Chert appear to be chytrids and zygomycetes. Documenting the occurrence of various fungal taxa and their interactions provides a unique opportunity to place these associations in an evolutionary context and to test hypotheses about the first appearance of such interactions, and to compare these associations with those known to exist today.