UF botanists: Flowering plants evolved very quickly int...(t of all green plant species diversified...)

The details, and especially the cause of, this diversification Darwins abominable mystery has been a hot topic in botany ever since.

One of the reasons why its been hard to understand evolutionary relationships among the major groups of flowering plants is because they diversified over such a short time frame, Jansen said.

Seeking to distill the cloudy picture into a clear one, the UF and UT researchers analyzed DNA sequences from the completely sequenced genomes of the chloroplast. That organelle, responsible for plants ability to photosynthesize, is shared by all green plants.

Jansen and his UT Austin colleagues analyzed DNA sequences of 81 genes from the chloroplast genome of 64 plant species, while the UF researchers analyzed 61 genes from 45 species. The two groups also performed a combined analysis, which produced evolutionary trees that included all the major groups of flowering plants.

Assisting the effort at UF was a newly purchased rapid gene sequencing machine.

UF was the first university to purchase this particular type of sequencing machine, Doug Soltis said. Where it would have taken months to sequence the chloroplast genome before, you can do it in a single day now.

By laboriously arranging the sequences, the researchers slowly built a kind of family tree for plants a diagram of relationships among plant lineages showing diversification over the eons. Based on known rates of genetic change double-checked against fossils of known ages, they established a time scale that revealed the dates of major branching events.

Based on the Soltises and their collaborators research in previous years, it was known that flowering plants split into three branches shortly after they appeared about 130 million years ago. That process was relatively gradual, at least compared with the rapid radiation that happened ne
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