A Long, Long Time Ago on Planet Not So Far Away
What were the first plants to colonize the land on Earth? And when did this occur in the history of the biosphere?
Why did a burgeoning of flowering plant species come to dominate their gymnosperm and fern predecessors so quickly?
The Mossy (Algal and Fungal) Earth
Most biology textbooks state that plant life emerged on land about 450 million years ago (e.g, see p.4, The Biology of Plants by Raven, Evert & Eichhorn).
A new study suggests that plants colonized land much earlier than this.
As summarized here, the authors L. Paul Knauth and Martin J. Kennedy think that their geochemical data suggests that photosynthetic life forms (largely mats composed of mosses and algae, accompanied by fungi) carpeted the land over 800 million years ago.
Their evidence, albeit indirect, may help to explain the increase in atmospheric oxygen levels that allowed for the evolution of relatively large respirating animals about 600 MYA.
This green “welcome mat” may have set the stage for animal colonization of the land.
The “Abominable Mystery” of the Conquering Flowers
It’s been over 100 years since Charles Darwin described it as an “abominable mystery”.
What was perplexing Darwin was the fossil evidence that flowering plants (angiosperms) rapidly diversified and spread across the planet. (This was at odds with his belief that evolution was a gradual process.)
A new theory has been proposed in an attempt to solve this “mystery”.
As brilliantly summarized here, flowering plants may have taken advantage of changes in soil fertility, which were due largely to the higher growth and turnover rates of angiosperms compared to gymnosperms. Thus, a sort of positive feedback loop was created that allowed for the rapid proliferation of flowering plant species.
The originators of this theory, Frank Berendse and Marten Scheffer, published this ecological explanation of Darwin’s “abominable mystery” in Ecology Letters.
Bottom Line: Looks like studying the soil can provide answers to botanical questions.
