The New York Times' Trilobites column has a story about work to understand how plants fit into the tree of life. New research detailed in the journal Nature suggests that more than 80% of major plant lineages evolved in a sudden burst during the Jurassic Period some 150 million years ago. This new study used DNA from the cell nucleus instead of the chloroplast that confirm previous results, but led to some surprising changes.
Previous evolutionary trees of plants built by scientists often used the genome of the chloroplast, the organelle that allows plants to perform photosynthesis. These genomes could be sequenced with older methods. But scientists could not be confident that the patterns they showed were the same as what might be revealed by the plant’s primary genome, stored in the cell’s nucleus and more difficult to study.
Then, five years ago, another scientific collaboration published detailed information about more than 1,100 plant species’ nuclear genomes. That allowed the team behind the Nature paper to design new tools for sequencing nuclear genes from a huge variety of flowering plants, said William Baker, who leads the Kew Gardens Tree of Life Initiative and is an author of the new paper.
They used the tools on living plants, but the team also reached out to institutions in 48 countries with collections of dried plants to get samples of rare specimens. Four of the plants included in the analysis are already extinct, including the Guadalupe Island olive, which was sequenced using a dried sprig from 1875. In the end, the team used data from about 60 percent of all modern genera of plants.As they put the new evolutionary tree together, they found that it confirmed many of the relationships suggested by trees built from chloroplasts. However, there were surprises: The new data reshuffled the relationships of a number of plant groups, and some individual species were reclassified.
