FLOWERS MADE YOU (SORT OF)
Why flowering plants were an evolutionary innovation arguably more significant to us than the death of the dinosaurs.
A modest flower ended up affecting life on Earth more than the huge bolide that wiped out the dinosaurs. Scientists have recreated the small plant, to which we owe our existence.
A4-m-long reptile with rows of huge spikes down its back is eating its way through the juicy, green leaves of a ginkgophyte. The animal is a Regnosaurus living in a region, which will be north-western Europe 140 million years later. In between its legs, much smaller dinosaurs move quickly about, benefitting from the twigs falling from the large herbivore’s jaws.
At the top of the high, conical tree, an Istiodactylus lands, folding up its learther-like wings. Its toothed beak is smothered in blood from the carcass that it had for breakfast.
None of the creatures notice that trapped between ferns and ginkgophyte roots, a small plant slowly unfolds its top leaves to greet the morning sun. The small plant will soon turn evolution upside down. It is Earth’s first flower, and in only 40 million years, its ancestors will take over the eco-systems of the world in a unique biological revolution.
Scientists have for the first time revealed what the ancestor of almost 90 % of modern plants looked like. And they are well on their way to finding out how the small flower defeated its competitors to finally pave the way for our own species: humans.
Flowers dominate the world
The descendants of the world’s first flower – known as flowering plants – now exist almost anywhere on Earth. So far, scientists have discovered some 300,000 different species, but another 100,000 are probably hiding in the tropical forests of the world.
The flowering plants do not only include the ones that we usually think of as flowers, such as sunflowers, tulips, roses, and dandelions. Leaf-bearing trees, fruit bushes, cactuses, and carnivorous plants also form part of the group. To humans, the most important ones might be grasses, including rice, sugar canes, wheat, corn, etc.
The central position in almost all ecosystems has made both palaeontologists and botanists explore the biology and origins of flowers, trying to find out what the first flower looked like, which type of plant it descends from, and why it took over Earth’s fauna, when the species that existed before it were apparently well-adjusted.
A major international research project has just answered one of the questions: what did the first flower look like? Scientists studied the appearances and genes of almost 800 modern plant species, and based on the results, they could figure out the characteristics of their common ancestor. The conclusion was that it was very much like modern flowers. All its characteristics still exist in flowers today – but not one flower is exactly like it.
In spite of its resemblance to the majority of modern plants, the first flower was quite unique in its time. Its new characteristics provided it with an evolutionary advantage: they allowed it to cooperate with animals on an unprecedented scale.
Insects assisted flowers
Flowers’ colourful petals function as signal lamps, attracting hungry insects. In order to get to a flower’s high-energy nectar, insects must push their way past stamens and stigmas. The stamens contain pollen, the flowers’ male gametes, which stick to the insect body. When the insect flies on to another flower, it deposits the pollen on the flower’s stigma – the exterior part of the plant’s female sex organ.
This reproduction method was very different from and much more clever than in earlier vegetation. Prehistoric plants only ejected their pollen or spores into the air or water, counting on them to land in the right place – just like their modern descendants such as ferns and pines do today. The pines improve their chances of hitting another tree’s female cones by making their male cones produce millions of pollen grains, but the extensive production wastes huge quantities of energy.
The flowers’ cooperation with insects ensures a surplus of energy, and the success was also beneficial to insects. According to studies, a few million years later, many new species of wasps, bees, ants, butterflies, moths, and flies emerged, whose life cycles were only based on flowering plants. They developed mouth parts that were particularly fit for extracting nectar, eating flower petals, or entering fruit. They also developed fur-like structures on their bodies, which efficiently collected pollen.
The success of the flowering plants did not only affect insects. Studies indicate that the explosive growth of flowering species takes place at the same time as a marked growth in the numbers of reptiles and birds. The dinosaurs were undoubtedly also affected by the major change of the ecosystems, but scientists have not yet found out how the large animals reacted to the radical change. Their bones apparently show no signs of adaptation to the new world.
According to some studies, we can thank the flowers for our existence. The group of mammals which humans and almost all other modern mammals belong to was only one of a series of mammal groups back then. And it was not by far the most successful one. However, the situation changed, when flowering plants conquered the world. Scientists propose that the drastic ecosystem
Unlike flowering plants, conifers and other gymnosperms do not "wrap" their seeds in high-energy fruit. SHUTTERSTOCK
change put most mammals under pressure, but our own omnivorous ancestors were sufficiently versatile to perform well during the challenging period.
Gene flaw caused success
The flowering plants went from nothing to making up to 80 % of the world’s vegetation in less than 40 million years – a split second in a major geological perspective.
Before flowers entered the scene, gymnosperms, ferns, etc., dominated Earth. Gymnosperms now i nclude pines, cycadophytes, and ginkgophytes, but in the era of the dinosaurs, there were also other types. Their heyday probably lasted some 150 million years – today only about 1,000 species remain on Earth. The majority of them are conifers, which exist in cool or mountainous regions. Today, scientists are almost certain that the first flower developed from an extinct group of gymno sperms. And they are also beginning to understand the genetic changes which triggered the development.
The major breakthrough came when they studied the primitive Amborella trichopoda
flowering plant, which now only grows on a small Pacific island 1,600 km east of Australia. The scientists sequenced the plant’s genes, only to discover that its ancestors’ DNA had changed radically about 160 million years ago. The change happened at least 20 million years before the time which prehistoric flora experts estimate to be the most probable for the evolution of the world’s first flower – and at least 30 million years before the oldest known fossilised flowering plant.
The marked change was a genome doubling – a genetic fertilization mishap, by which the fertilized egg cell got twice as many copies of its own genes as normally. In animals, such a mishap will result in the offspring becoming sterile or dying during the embryonic stage or shortly after birth.
But in plants, there is a slight chance that the individual survives and is even able to reproduce. According to the scientists, the extra genes can make sure that the plant and its descendants are better protected against harmful mutations. If a mutation destroys one copy of a gene, three others can take over. The biggest advantage might be that the extra genes could develop into new genes with other functions over time.
The genome doubling in flowering plant ancestors consequently laid the foundation of the ground-breaking characteristics that triggered their success.
Flowers most important event
Today, the flowering plants are not just the most species-rich group of plants, but also the most diverse. It includes anything from the only 2-mm-wide members of the duckweed family to the more than 100-m-high Australian giant eucalyptus.
Furthermore, the success is emphasised by the fact that scientists have not yet found fossils of prehistoric flower families, which have gone extinct at a later point in time. In other words, the combination of flowers, nectar, and cooperation with insects was so ingenious that none of the larger groups of flowers, which have emerged over the past 140 million years, have ever disappeared again.
Flowering plants have adapted to life in the driest deserts of the world, on the highest mountains, and on the ocean floor. And only a few environments on Earth are not completely dominated by the successful plants. Gymnosperm conifers are still the most numerous in northern forests. But it is not by far unthinkable that the flowering plants will at some point become able to out compete the die-hard conifers on their own home turf.
The complete dominance of the plant kingdom and the huge influence on the world’s fauna has made some palaeontologists point out the first flower’s emergence as one of the most important events in Earth’s history. Over a period of 40 million years, during the heyday of the dinosaurs, the small growths managed to alter life in the world, preparing the plant and animal groups that rule the world today for success. Not even the huge meteor that struck Earth 66 million years ago, wiping out the dinosaurs, was able to change what the flowers had produced.
THE WORLD'S FIRST FLOWER CONQUERED EARTH.
The first flower, which emerged in the era of the dinosaurs, probably had a diameter of less than 1 cm.