Researchers from Nanjing Normal University (NNU) have found the evolutionary timescale of green plants.
Their paper entitled “Accounting for uncertainty in the evolutionary timescale of green plants through clock-partitioning and fossil calibration strategies” was published online in the journal Systematic Biology, on May 6, 2019. Systematic Biology, with a five-year comprehensive impact factor of 14.50, is one of the leading journals worldwide in terms of evolutionary biology.
The findings were made by the research group led by Prof. Bojian Zhong of the School of Life Sciences. Prof. Zhong is the corresponding author of this paper and NNU postgraduate Yuan Nie from the School of Life Sciences is the lead author.
Viridiplantae or green plants, are a clade of eukaryotic organisms made up of perhaps 500,000 species. Extensively distributed, they play an important role in global climate system. Establishing an accurate evolutionary timescale for green plants, therefore, is essential to understanding their interaction and coevolution with the Earth’s climate and the many organisms that rely on green plants.
Despite being the focus of numerous studies, the timing of the origin of green plants and the divergence of major clades within this group remain highly controversial.
In this study, however, by using Bayesian molecular dating, the research group presented divergence-time estimates of the major groups of green plants that take into account various sources of uncertainty. The analyses yield date estimated ranging from the Paleoproterozoic to Mesoproterozoic for crown-group green plants (1679.7-1025.6 Ma), and from the Ediacaran to Middle Ordovician for crown-group land plants (559.3-459.9 Ma). In addition, this study showed that (1) from the middle proterozoic to the new proterozoic (~1200-750 Ma), the eruption of early green plants (green algae) increased the emission of dimethyl sulfate, and the oxidation of dimethyl sulfate into cloud condensation nuclei led to the decrease of global temperature, thus promoting the formation of “Snowball Earth”. (2) the Gaskiers ice age at the end of the neoproterozoic bound a large amount of water together, which resulted in the global climate becoming dry, and many fresh water sources drying up, thus forcing freshwater algae to adapt to a land habitat and eventually forming land plants.
The result lays the foundation for further investigations into the origin and evolution of green plants and how they shaped the global climate and ecosystems.
This research was supported by the National Natural Science Foundation of China, the Key Project of Natural Science Foundation of Jiangsu Higher Education Institutions of China, Qing-Lan Project of Jiangsu Province etc.