Microsclerotia of dark septate endophytic fungi from Paleogene and Neogene of Poland: fossil record and palaeoenvironmental significance of root fungal endophytes

Remains of microsclerotia morphologically corresponding to those of modern dark septate endophytic (DSE) fungi were found during palynological studies of some Oligocene and Miocene sites from Poland. Fossil microsclerotia, mostly represented by leaf-like morphotypes were morphologically diversified, but there was no possibility to match the fossil morphotypes with modern fungal DSE taxa forming microsclerotia in roots. Reliable fossils of microsclerotia of dark septate endophytic fungi date back to the Eocene and show continuous presence till recent times. They confirm the coexistence of dark septate endophytic fungi with plants at least from the beginning of the early Cenozoic. Pre-Cenozoic fossils of presumed DSE microsclerotia were considered doubtful. The presence of microsclerotia in continental deposits points to dense vegetation in the past, and in marine deposits, they indicate terrigenous flux that originated from coastal vegetation.