The First Flower?
How did flowering plants (angiosperms) evolve from non-flowering seed plants (gymnosperms)? Or did they?
When did the first flower appear on this planet?
And where on Earth did it occur?
These are some of the most hotly debated questions among botanists today. Partly because some of the fossil data is at odds with some of the DNA data.
An article by Elizabeth Pennisi in a recent issue of Science magazine prompted this blog post, in which I’ll try to summarize the current evidence and opinions. (Click here to listen to an interview with Pennisi regarding her essay on the origin of flowering plants.)
(Even though it’s somewhat outside the realm of “how plants work”, it’s still very a interesting topic, no?)
Goodbye Naked Seeds
Non-flowering gymnosperms, such as conifers, bear naked seeds on scales. Angiosperms have seeds encased in remnants of the flower.
Gymnosperms arose about 370 million years ago and dominated the Earth for 250 million years. Then within a few tens of millions of years, angiosperms appeared and their species greatly proliferated. (Currently almost 9 out of 10 land plant species are angiosperms.) This is the “abominable mystery” that confounded Charles Darwin. That is, how flowering plants diversified and spread so rapidly across the planet. (Still, today, 130 years after Darwin’s lament, this remains a perplexing topic among botanists…. a topic for another time.)
The Missing Link?
Where are the intermediates between the gymnosperm to angiosperm transition?
In 2002, there was much excitement over the fossil discovery of Archaefructus (illustration on left). This aquatic seed plant fossil was initially dated to the late Jurassic, about 145 million years ago, making it the earliest example of an angiosperm.
But since 2002 this fossil has been found to be not as old as originally thought, only about 125 MYA, and some scientists think it may be a member of the water-lily family.
This would render Archaefructus less primitive than Amborella, which currently sits at the bottom of the angiosperm family tree.
Amborella (see photo at top of the post) is a small shrub with tiny greenish-yellow flowers and red fruit that grows only in the understory in the rain forests of New Caledonia.
The simple answer to the question “Where is the missing link?” is: currently, there isn’t any.
The fossil data are incomplete and difficult to interpret. The molecular (DNA analysis) data from living plants group the gymnosperms all together and the angiosperms all together, with no plant species in between.
The missing link may have gone extinct. And, short of a very fortuitous fossil discovery, it may never be found.
Pertinent Links:
Nova (PBS) program on the first flower
The Deep Time Project (featuring Archaefructus)
Bottom line: Where and how flowering plants arose on Earth about 130 MYA is still very much an unsolved mystery.
