Washington, Nov 27: A new study by scientists has shed light on early plant evolution by finding that flowering plants had evolved into five groups in a short period of less than 5 million years.

The study, carried out by Doug and Pam Soltis, a UF (University of Florida) professor of Botany, shows that a stunning diversification of flowering plants took place in the period of less than 5 million years, and resulted in all five major lineages of flowering plants that exist today.

"Flowering plants today comprise around 400,000 species," said Soltis. "So to think that the burst that give rise to almost all of these plants occurred in less than 5 million years is pretty amazing, especially when you consider that flowering plants as a group have been around for at least 130 million years."

Botanists predating Darwin have long recognized that flowering plants, which comprise at least 60 percent of all green plant species, diversified abruptly shortly after they appeared.

Based on the research in previous years, it was known that flowering plants split into three branches shortly after they appeared about 130 million years ago.

But the latest research clears the picture by showing that all plants fall into five major lineages that developed over the relatively short period of 5 million years, or possibly even less.

The details and cause of this diversification has been a hot topic in botany ever since.

"One of the reasons why it's been hard to understand evolutionary relationships among the major groups of flowering plants is because they diversified over such a short time frame," said Robert Jansen, professor of integrative biology at The University of Texas at Austin.

To make things clearer, the 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.

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.

"As for the cause of the diversification, it remains mysterious," said Pam and Doug Soltis. "It's possible it was spurred by some major climatic event. It's also possible that a new evolutionary trait – a water-conducting cell that transfers water up plant stems – proved so effective that it spurred massive plant species diversification," they added. (ANI)