Ancient molecules on fossil leaves reveal relationships among Jurassic-era plants

July 6 (UPI) -- Thanks to a new molecular analysis technique, researchers have established relationships among 200-million-year-old plants for the first time.

The findings -- detailed in the journal Nature Ecology and Evolution -- offer new insights into the habitats in which dinosaurs lived.

Without genetic data, relationships among ancient plants have been difficult to establish. The earliest plant DNA fragments found to date are only 1 million years old.

"We have solved many questions regarding these extinct plants' relationships," Vivi Vajda, a professor at Sweden's Lund University, said in a news release. "These are questions that science has long been seeking answers to."

DNA has proven incapable of surviving intact for millions of years, so scientists turned their attention to organic molecules. Infrared spectroscopy allowed scientists to identify communities of biomolecules in the waxy membrane of Jurassic-era fossil leaves.

To start, scientists studied the collections of organic molecules found in the membranes of modern plant leaves. They found consistent biomolecular patterns among groups of related plants. The biomolecular signatures allowed scientists to identify plants in a manner similar to DNA analysis.

"The results from the fossil leaves far exceeded our expectations, not only were they full of organic molecules, they also grouped according to well-established botanical relationships, based on DNA analysis of living plants i.e. Ginkgoes in one group, conifers in another," said Vajda.

The research allowed scientists to begin grouping ancient plants according to common biomolecular signatures. So far, researchers have shown two groups of Triassic- and Jurassic-era plants, Bennettites and Nilssonia, are closely related.

"The great thing about the biomolecules in the leaves' waxy membranes is that they are so much more stable than DNA," said Per Uvdal, professor of chemical physics at Lund. "As they reflect, in an indirect way, a plants DNA they can preserve information about the DNA. Therefore, the biomolecules can tell us how one plant is related in evolutionary terms to other plants."