Mycorrhizal symbiosis in the Paleozoic seed fern Glossopteris from Antarctica

Abstract

Mycorrhizal associations occur in almost all modern plant groups and are probably one of the most important forms of symbioses in the context of terrestrial ecology and evolution. Surprisingly, there is a paucity of information regarding the occurrence of mycorrhizal symbioses in extinct plant groups. We report the first evidence of endomycorrhizal associations in the seed fern order Glossopteridales based on structurally preserved (permineralized) fossils from the Permian of Antarctica. The fungus, Glomites vertebrariae sp. nov., is characterized by septate hyphae that colonize the cortical cells of Vertebraria in a serpentine or helical pattern that closely resembles modern Paris-type mycorrhizae. Also present are intercellular vesicles. The fungus is only found in young rootlets, suggesting that the mycorrhizae played an essential role during the early establishment of the roots. The discovery of this plant–fungal association provides unequivocal evidence for the antiquity of mycorrhizal associations in seed plants. In addition, it also provides further insight into the structure of Gondwanan Permian paleoecosystems. Fungal associations, together with data on the anatomy and physiology of Glossopteridales, offer insights that may help to explain the dominance of these seed ferns in the Permian of Gondwana.