From rainforest to herbland: New insights into land plant responses to the end-Permian mass extinction

The end-Permian mass extinction is the greatest biotic crisis in Earth history causing the extinction of a large number of marine and terrestrial animals globally. However, how land plants responded to the catastrophe remains controversial. The successive plant-bearing beds in China provide a unique window into the great vegetation change through the critical Permian-Triassic time interval. A notable monospecific vegetation comprising a new isoetalean, Tomiostrobus sinensis Feng, is documented from the lowermost part of the coastal Kayitou Formation in Southwest China. The new plant is a diminutive, heterosporous lycophyte, which formed ground-covering communities infringing the oligotrophic lakes along coastal regions. The apparent occurrence of T. sinensis immediately above the uppermost coal bed demonstrates that the enigmatic gigantopterid-dominated rainforest ecosystem suddenly collapsed and was replaced by the isoetalean-dominated herbaceous vegetation in the tropics of the eastern Tethys. Our study indicates that the magnitude of vegetation response to the end-Permian mass extinction in different palaeophytogeographic regions is probably largely affected by the latitudinal gradients of biodiversity and ecological stress. Because of the complexity of local palaeoenvironmental, palaeoclimatic and palaeotopographic conditions, it is unlikely that a unified global pattern and timing of land plant response to the end-Permian mass extinction can be obtained.