DNA TREE OF PLANT LIFE RESOLVES DARWIN'S 'ABOMINABLE MYSTERY'

DNA Tree of Plant Life Resolves Darwin's 'Abominable Mystery'

Global team led by the Kew Royal Botanic Gardens analyzed over 9,500 flowering plants to figure out how so many evolved, so fast

April 24th, 18PM April 24th, 18PM

Flowers are attractive, which is one of life's few true axioms. That is their whole point. They attract bees and other pollinators such as bats, which help the plant bearing the flowers to disseminate. Today flowering plants account for 90 percent of all terrestrial plant life and exist on all continents, but while they delight everyone from bees to bats to courting couples, they sorely troubled Charles Darwin, co-parent of evolution theory.

To Darwin, the plants with the pretty genitals posed an "abominable mystery." The mystery was the explosive diversification of flowering plants so shortly after their emergence.

New light has been shed on the enigma by a giant genomic study encompassing over 9,500 plants, published in Nature by a multinational team of 279 scientists led by the Kew Royal Botanic Gardens. Over 8,000 of the subject plants are flowering ones, the team writes. And what did they find?

Suddenly, life

The origin of life is one of the great mysteries. The earliest form may go back more than 4 billion years. What it was like, we do not know. Some sort of animal? Some sort of phototroph that would evolve into plants?

Almost certainly neither, but a primitive precursor single cell that ate neither other cells nor the energy of sunlight. It was likely a chemitroph that utilized either organic or inorganic molecules as sources of energy.

Some think that precursors to autotrophic plants, which make their own food from sunlight, energy and carbon dioxide, were not far behind. Cyanobacteria, aka blue-green algae, may go back 3 billion years, or two, or less, maybe more – argument rages on about signals of oxygen production in rocks, and claims of very ancient fossil bacterial mats. But the story of plant evolution more usefully centered on fossils tentatively suggested to be phytoplankton or fossil green algae in the Cambrian over half a billion years ago.

The earliest terrestrial plants are assumed to have evolved from green algae that survived in shallows, then on land. Paleontologists point to proof of terrestrial plants appearing in the Ordovician, from about 490 million years ago: spores. These were plants, they were on land, and they had a common ancestor with green algae.

Well and good. Plants had arrived and come the Siluran era, vascular plants began to emerge. They began with simply branching creatures but by the era's end, complex vascular plants were spreading around the world. By the time of the Devonian, a delightful time for bugs and centipedes and the like, flowering plants were all the planetary rage (and had primitive parasites, arthropod enthusiasts point out).

Forests began to cover the land, not that we would recognize them for their trees. The first proper seed plants as know them also began to appear.

And around 140 million years ago, paleontologists have deduced, flowering plants emerged and took over. They rapidly came to dominate over non-flowering vascular plants, going by the fossil record (which is the record of things we found, not the record all things that were).

Darwin's bewilderment was at the apparent sudden emergence of such diversity. As the authors of the new paper explain, he wrote to Joseph Dalton Hooker of Kew: "The rapid development as far as we can judge of all the higher plants within recent geological times is an abominable mystery."

Now in the new paper, based on a vast amount of genetic data from (specifically) 9,506 species, plus information from the fossil record, the authors have redrawn the pace of growth by the tree of plant life.

Suddenly, cold

And what picture did they draw? Firstly, they did confirm that flowering plants emerged about 140 million years ago and when they did, their diversity did explode. They were a huge hit. Flowers are attractive…. More than 80% of the flowering lineages existing today originated in that window of time, the research team led by Kew found.

And then, they discovered, matters steadied for about 100 million years or so, after which climate change drove another spike of diversification in flowering plants 40 million years ago.

What climate change? A chill. This is most decidedly not the scenario we face today.

Would Darwin have felt gratified? The underlying conundrum of rapidly driven evolution upon the plants' emergence remains to a degree, but one could argue flowers were really, really attractive.

"The sheer amount of data unlocked by this research, which would take a single computer 18 years to process, is a huge stride towards building a tree of life for all 330,000 known species of flowering plants – a massive undertaking by Kew's Tree of Life Initiative," Kew said in a statement.

Kew also stressed the value of work by long-gone botanists who lived, collected specimens and died before we knew anything about DNA and genomic analysis.

"The vast treasure troves of dried plant material in the world's herbarium collections, which comprise nearly 400 million scientific specimens of plants, can now be studied genetically. Using such specimens, the team successfully sequenced a sandwort specimen (Arenaria globiflora) collected nearly 200 years ago in Nepal and, despite the poor quality of its DNA, were able to place it in the tree of life," Kew stated. Thusly they could also analyze extinct plants such as the Guadalupe Island olive (Hesperelaea palmeri), which is believed to have died out in 1875.

The team at Kew hope this vast treasure of information they have collected will help us Homo sapiens, who evolved in a startlingly short span of time, somehow cope with the crisis of biodiversity we are creating.

2024-04-24T15:08:29Z dg43tfdfdgfd