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Atmospheric oxygen as a driver of plant evolution over the past 400 million years (OXYEVOL)
Date du début: 1 févr. 2012, Date de fin: 31 janv. 2017 PROJET  TERMINÉ 

"The evolution of complex organisms over one billion years ago is intimately linked with a rise in atmospheric oxygen levels (O2) over a critical threshold that would support essential metabolic processes. Over the past 500 million years O2 has varied between lows of 10% to highs of 35%, compared with current ambient levels of ~21%.Critical events in animal evolutionary history have been linked with shifts in atmospheric O2 such as the origination and radiation of mammals and selective extinction of many land vertebrate groups, at three of the five great mass extinction boundaries. The potential role of O2 as a driver of plant evolution has been almost completely overlooked, despite evidence from space science which shows that sub-ambient O2 can negatively impact all aspects of plant reproduction, phloem loading and photosynthesis. This proposal will address this severe gap in our knowledge of the importance of O2 in shaping patterns in plant evolution, by investigating the role of long-term trends in atmospheric O2 on the timing of major reproductive and vegetative innovations in the plant fossil record. This palaeobotanical approach utilizing the plant fossil record will be coupled with a series of highly novel ‘atmospheric miniworld’ experiments where representative plant taxa from all three major reproductive grades will be subjected to the atmospheric O2:CO2 conditions into which they likely originated and diversified. We will address whether tipping points in the ecological dominance of different evolutionary groups of land plants (angiosperms/ gymnosperms/ pteridophytes) were driven by shifts in prevailing atmospheric O2 content. We will achieve these objectives by conducting controlled competition experiments incorporating all three reproductive grades in miniworlds with differing atmospheric O2:CO2 ratios."