University of Florida and University of Texas at Austin scientists have determined the two largest groups of flowering plants are more closely related to each other than any of the other major lineages. Those are the monocots, which include grasses and their relatives, and the eudicots, which include sunflowers and tomatoes.

The researchers also showed a major diversification of flowering plants occurred during a comparatively short period of less than 5 million years, resulting in all five major lineages of flowering plants that exist today.

"Flowering plants today comprise around 400,000 species," said Pam Soltis, one of the UF researchers. "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."

The research is to appear in next week's issue of the Proceedings of the National Academy of Sciences.