The evolutionary emergence of land plant body plans transformed the planet. However, our understanding of this formative episode is mired in the uncertainty associated with the phylogenetic relationships among bryophytes (hornworts, liverworts, and mosses) and tracheophytes (vascular plants).
Researchers from UK and China shows that the first plants to conquer land were a complex species, challenging long-held assumptions about plant evolution.
They report a new family tree 'Setaphyta', which stays that the liverworts and mosses are now united in a new group, in Current Biology. Prof. Harald Schneider of Xishaungbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences is one of the three correspondence authors of the study.
By modelling the molecular sequences of modern plants, the researchers analyzed a large transcriptomic amino acid alignment from 103 species of algae (Chlorophyta and Streptophyta) and Embryophyta (mosses, hornworts, liverworts, and tracheophytes).
They used an extensive molecular dataset and sophisticated models for evolution to understand which plant group was the first to conquer the land from their algal ancestry.
The results showed that liverworts are more closely related to mosses than hornworts. The liverworts and mosses are now united in a new group, 'Setaphyta'.
The new family tree of plants with the Setaphyta group shows that liverworts were not the first group to conquer land, and liverwort simplicity reflects the loss of features, not ancestral simplicity.
"As our new tree of plant relationships indicates that the first land plants were more complex than liverworts, we will have to re-evaluate our assumptions on the evolution of land plants," said Prof. Harald Schneider.
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