Dr. Bojian Zhong's group has made an important breakthrough on the origin and evolution of land plants. The article, entitled "Large-scale phylogenomic analyses reveal the monophyly of bryophytes and Neoproterozoic origin of land plants", was published in Molecular Biology and Evolution. This research strongly recovered the monophyly of bryophytes using a large nuclear dataset and supported that crown embryophytes originated in the Neoproterozoic (980–682 Ma), much older than widely recognized (450–500 Ma).

 

 

This study focuses on the evolutionary relationships of early land plants and the timing of the origin of land plants. Based on the large-scale phylogenomic data sets (1,440 genes, 123 taxa), this study explored the impact of systematic errors on the reconstruction of early land plant evolutionary relationships. The results have shown that phylogenomic analyses based on amino acid data and Dayhoff-recoded data strongly supported monophyletic bryophytes; while the inference of paraphyly of bryophytes based on the nucleotide data is caused by fast-evolving synonymous substitutions. In evolutionary time estimation, fossil calibrations and molecular data are the crucial sources of actual biological information. Changing the calibrations will obviously influence time estimation, considering the importance of fossil calibrations in time priors. Based on the reliable phylogenetic relationships of land plants, this study used 22 fossil calibrations and three different fossil calibration strategies to estimate the origin time of land plants. By comparing user priors, effective priors, and posteriors, this study gained insight into why past studies have differed widely in their estimated time of the origin of land plants. The results found that narrow fossil calibration interval is informed more by fossil constraints. In contrast, a more relaxed fossil calibration strategy allows the molecular data contributed the information relevant to the age of embryophytes and the age estimates were not entirely driven by prior. By considering the reliability of fossil calibrations and the influences of molecular data, this study estimate that land plants originated in the Precambrian (980−682 Ma).

 

The origin and evolution of land plants

                       

This study highlights the important contribution of molecular data when faced with contentious fossil evidence, while providing a novel perspective for assessing optimal fossil calibration strategies. The results of this study provide the foundation for accurate interpretation of the development of plant traits during the water-to-land transition.

This research has been published in Molecular biology and Evolution (https://doi: 10.1093/molbev/msab106) with graduate student Danyan Su and doctoral student Lingxiao Yang as the first authors and Professor Bojian Zhong as the corresponding author.