Flowers discovered perfectly preserved in blocks of amber bloomed at the feet of dinosaurs, suggesting that some flowering plants in South Africa remained unchanged for 99 million years, reveals a new study published in the journal Nature Plants on Monday.
The two plants flourished in what is now Myanmar and may shed light on how flowering plants evolved — an important episode in the history of life that Charles Darwin once described as an “abominable mystery”.
Flowers are ephemeral: they bloom, turn into fruit and then disappear. As such, ancient flowers are not well represented in the fossil record, making them—and the history they carry—particularly precious.
“Leaves are usually produced in greater numbers than flowers and are much more robust, in addition to having greater potential for preservation. A leaf is discarded ‘as is’ at the end of its lifespan, while a flower develops into a fruit, which is then eaten or disintegrated as part of the seed dispersal process,” said study author Robert Spicer, professor from the Open University’s School of Environmental, Earth and Ecosystem Sciences, UK.
“These particular flowers are almost identical to their modern relatives. There are really no big differences,” added Spicer, who is also a visiting professor at the Xishuangbanna Tropical Botanical Garden in China.
The evolution and spread of flowering plants (angiosperms) is believed to have played a key role in shaping much of life as we know it today, such as the diversification of insects, amphibians, mammals, and birds, and ultimately marked the first time when life on land became more diverse than at sea, according to the study.
“Flowering plants reproduce faster than other plants, they have more complex reproduction mechanisms — a wide variety of flower forms, for example, often in close ‘collaboration’ with pollinators. This drives the mutual co-evolution of many plant and animal lineages, shaping ecosystems,” Spicer said.
One of the flowers preserved in amber was named by researchers Eophylica priscatellata and the other Phylica piloburmensis, the same genus as the Phylica flowers that are native to South Africa today.
Mystery solved?
The sudden appearance of flowering plants in the fossil record in the Cretaceous period (145 million to 66 million years ago), with no obvious ancestral lineage from earlier geological periods, intrigued Darwin. It seemed to be in direct contradiction to an essential element of his theory of natural selection – that evolutionary change occurs slowly and over a long period of time.
It was in a private letter to the botanist Joseph Hooker in 1879, published in a 1903 volume of Darwin’s letters, that he described it as an “abominable mystery”.
Exactly when the flowering plants emerged is still unclear, Spicer said, but the first flowers preserved in amber shed some light on the mystery.
The specimens exhibit characteristics identical to those seen on flowers in fire-prone areas such as the unique fynbos biome regions of South Africa. All 150 species of Phylica are native to this biologically rich and diverse region. They were also found next to an amber that contained partially burned plants.
“Here we have preserved in amber all the details of one of these early flowers just at the time when flowering plants begin to spread across the world, and it shows an excellent adaptation to seasonally dry environments that sustain vegetation exposed to frequent forest fires,” he said. Spicer.
“If many of the first flowers were exposed to fire in such semi-arid landscapes, this explains why the early stages of angiosperm evolution are so poorly represented in the fossil record — fossils do not normally form in semi-arid areas,” he added.
Spicer said that fire must have been a frequent event over a long period of time for evolution to have shaped flowers into a shape that could handle fire and produce seeds that could find their way to the surface of the scorched earth. In the case of Phylica, its flowers are protected by leaves that cluster at the tip of the branch.
While many ferns, conifers and some flowering plants seen today such as plane trees and magnolias grew during the times of the dinosaurs.
Spicer said that Phylica piloburmensis was the first flowering plant known to have a nearly identical relative alive today.
Dinosaur-era amber fossils are found only in deposits in northern Myanmar’s Kachin state, and ethical concerns related to human rights abuses over the region’s amber provenance have arisen in recent years.
The Vertebrate Paleontology Society called for a moratorium on research into amber sourced from Myanmar after 2017, when the country’s military took control of some amber mining areas.
Spicer said the amber was purchased from local sellers before 2016 and was legally sourced under the rules in effect at the time.
Source: CNN Brasil
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