Palaeogene: Low CO2 concentrations favoured grasslands

A team led by LMU researcher Sebastian Höhna reports in Nature Communications.

Ecosystems on our planet have changed from dense forests to open-habitat ecosystems such as grasslands which provide resources for large grass-feeding mammals (e.g., horses). A team led by Sebastian Höhna, head of an Emmy Noether research group at the GeoBio-Center at LMU, now have analyzed the timing of the radiation of grasslands’ most important plant families (grasses and daisies) using information provided by time-calibrated molecular phylogenies and a novel Bayesian statistical model. The scientists found that the most important diversification of grasses and daisies occurred about 20 million years ago. Interestingly, the onset of the diversification of grasslands appears to have occurred just after a significant global drop of atmospheric CO2. Plants absorb carbon dioxide and release oxygen and water vapour through stomata in their leaves. Low CO₂ concentrations trigger opening of stomatal pores which increases the loss of water. The scientists assume that carbon limitation and water stress due to lower atmospheric CO2 favored grasslands at the expense of forests.