Fungus–plant interaction in a Thuringian (Late Permian) Dadoxylon sp. in the SE Iberian Ranges, eastern Spain

Abstract

This report describes an anatomical and taphonomical study of a large, exceptionally well-preserved Late Permian Dadoxylon sp. trunk. The specimen, found in siliciclastic red bed sediments of fluvial origin of the Landete Formation, Iberian Ranges, eastern Spain, includes the first described fungus–plant interaction for this time interval in Europe. This finding is all the more significant since a “fungi-enriched layer”, recently reported in sediments of different continents corresponding to the end of the Permian, has been related to a world-wide crisis, whereby fungi were responsible for the breakdown of massive amounts of vegetation–already suffered by a possible catastrophic event or events–leading to a global drop in photosynthesis. The well-known humid, temperate climatic conditions of the Late Permian sediments and the sedimentary environment represented by the Landete Formation would have favoured the proliferation of fungi which was probably unaffected by any other significant biotic activity. Fungal activity is likely to have started soon after the fall of the plants, indicated by the good preservation state of areas of the trunk unaffected by the fungal infection. Later diagenesis suggests different fluid migration stages, clearly conditioned by the original anatomical characteristics of the trunk and the results of fungal activity. Physical signs left by the enzyme action of wood-decay fungi can be recognised in the fossilised wood. Using this information and sedimentological data, we reconstructed the taphonomic processes incurred by the specimen, including both biostratinomic and diagenetic stages. Ullmania sp. and pollen grains such as Lueckisporites and Nuscoisporites dulhuntyi produced by species of Late Permian Walchiaceae or Ullmanniaceae that did not cross the Permian-Triassic boundary were also found in levels stratigraphically below the fossil specimen; none occurred above the trunk site. This flora and fungal activity could relate this level of Iberian Permian sediments to the level or one of the levels associated with the worldwide Late Permian crisis and fungal proliferation.