During the end-Permian ecological crisis, terrestrial ecosystems experienced a dieback of woody vegetation. Across the world (fig. 1), surviving herbaceous lycopsids played a pioneering role in repopulating deforested terrain. The microspores of these lycopsids were regularly released in unseparated tetrads (fig. 2). Although involvement of mutation has long been hinted at or proposed in theory, this finding provides the first concrete evidence for chronic environmental mutagenesis at the time of global ecological crisis. Prolonged exposure to enhanced ultraviolet radiation could account satisfactorily for a worldwide increase in land plant mutation. At the end of the Permian, a period of raised ultraviolet stress may have been the consequence of severe disruption of the stratospheric ozone balance by excessive emission of hydrothermal organohalogens in the vast area of Siberian Traps volcanism.
Visscher H., Looy C.V., Collinson M.E, Brinkhuis H., Van Konijnenburg-Van Cittert J.H.A.. Kürschner, W.M., and Sephton, M.A., 2004. Environmental mutagenesis during the end-Permian ecological crisis. Proceedings National Academy of Science 101: 12952-12956.PDF
Pfefferkorn, H.M., 2004. The complexety of mass extinction. Proceedings National Academy of Science 101: 12779-12780.PDF
|End-Permian Isoetalean spore tetrads|