World's Oldest Flowering Plant Came From the Water

08-17_Montsechia_ancient_plant
A fossil of Montsechia, which came onto the scene about 130 million years ago, making it the oldest known flowering plant. Gomez et al/PNAS

Scientists have long thought that the first flowering plant in history would be a land plant. Though a few angiosperms (the scientific name for flowering plants) around today occur in the water, most live on land, and it has been generally assumed that these types of plants evolved on terra firma before radiating back out into the water, says Indiana University paleobotanist David Dilcher.

But that may not be the case. A paper published August 17 in the journal Proceedings of the National Academy of Sciences has identified the oldest flowering plant found to date, an aquatic species fossilized in deposits in modern-day Spain.

Dilcher and colleagues from France, Germany and Spain have shown that fossils of a plant known as Montsechia vidalii came on the scene between 130 million and 124 million years ago. It's hypothesized that terrestrial angiosperm had already appeared at the time, although the current find predates any known terrestrial specimens. Montsechia also predates the oldest known angiosperm, Archaefructus, which came in 124.5 million years ago.

Montsechia reconstruction
A rendering of what Montsechia, the ancient aquatic flowering plant, actually looked like. O. Sanisidro, B.G., and V.D.G. / PNAS

"Flowers are all about sex," Dilcher says. The great advance of angiosperms was to co-opt the behavior of animals, getting them to carry their pollen to other individuals of their species (wind, of course, can also do the job). This creates more diverse offspring than does self-fertilization, regeneration or the production of asexual spores, which is, for example, how ferns reproduce. But another way to spread your seed, so to speak, is by using water currents, as Montsechia did. And "right at the start [of angiosperm evolution], this was another method that flowering plants were using for their genetic exchange," Dilcher says.

Modern-day descendants of Montsechia, known as Ceratophyllum, appear quite similar to their ancient descendants and are found in lakes on every continent. The six existing species release a pollen-containing sac called an anther, which floats to the surface and then ruptures to release pollen grains. These are then carried by currents and, if all goes well, fertilize primitive flowers in other Ceratophyllum plants. These plants lack roots and petals, and have simple, tiny flowers that contain a single seed, according to the study.

"We don't know, and it's difficult to say, that this is the first flower in the world," Dilcher says. (Though it is the oldest found to date.) These underwater plants almost certainly had a large, and underappreciated, role in the early and subsequent evolution of angiosperms, he adds.

This study helps "to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence," writes Donald Les, a University of Connecticut expert in plant evolution who was not involved in the study, in a commentary in the same journal.