Format: ORAL

Christine Strullu-Derrien1,2, Alan RT Spencer1,3, Frederic Fercoq4, Raymond Wightman5, Paul Kenrick1, Sebastian Schornack6, David Hawksworth7,8,9, Andrew H Knoll10

1. Science Group, The Natural History Museum, London, UK 2. Institut Systématique Évolution Biodiversité, Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, Paris, France 3. Department of Earth Science & Engineering, Imperial College London, London, UK 4. Unité Molécules de Communication et Adaptation des Micro-organismes, Muséum national d’Histoire naturelle, CNRS, Paris, France 5. Sainsbury Laboratory, University of Cambridge, Imaging facility, Cambridge, UK 6. Sainsbury Laboratory, University of Cambridge, Cambridge, UK 7. Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, UK 8. Jilin Agricultural University, Changchun 130118, Jilin Province, China 9. Geography and Environmental Science, University of Southampton, Southampton, UK 10. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA

Sites of exceptional preservation such as the Devonian Rhynie cherts (Scotland, UK) and the Carboniferous Esnost chert and GrandCroix cherts (Massif Central, France) preserve remarkable records of early terrestrial ecosystems. The cherts at Rhynie formed as deposits from a hot spring system. Fossilization occurred through episodic inundation of the biota with fluids from a nearby hot-spring system, and the resulting silicification preserved organisms in exquisite detail. Alongside plants, a community of animals, primarily arthropods, and diverse microscopic organisms, including cyanobacteria, algae, amoebozoa, oomycetes and various fungal groups have been described from these sites. At Esnost cherts formed in acidic volcanoclastic sediments associated with peat deposits (now anthracites). At GrandCroix silicification of the plants was related to silica-charged waters produced during chemical weathering of earlier volcanics. Fossilization preserves both in situ plants and transported plant fragments. Preservation is excellent, but the plant remains are fragmentary. In addition to plants, fungi and oomycetes have been documented. The development of Confocal Laser Scanning Microscopy (CSLM) has provided us with a new tool to investigate the biodiversity of these unique sites. Unlike traditional bright-field microscopy, CSLM enhances the images clarity and detail. Recently we used Fluorescence Lifetime Imaging (FLIM) that delivers information about the spatial and chemical distribution of fluorescent material together with information about its nano-environment. These approaches allow us to document minute three-dimensional structures with unprecedented precision. We will present our latest findings on cyanobacteria, testate amoebae, fungi and oomycetes from the Rhynie chert, showing that the components of the bacterial mats among which plants grew were already highly diversified. With the addition of new results on symbiotic and pathogenic fungi and of the newly described oomycetes from the French cherts, we will show an increasing knowledge of the diverse interactions that took place in early terrestrial ecosystems.