Why is this species on the way to evolution, the harder it is, the more unfortunate it is
The heterogeneity of the evolution rate of different groups of organisms and different time periods is widespread in organisms, but the mechanism of the heterogeneity is not clear. It may be related to its own genetic and morphological characteristics, but it is also related to other organisms and living environments. Related.
Dong Liping
Associate Researcher, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences
It is generally believed that in the process of biological evolution, many large branches of evolution have emerged through rapid evolution, and they have higher biodiversity; while smaller branches have undergone slower evolution, and their biological diversity Lower.
However, in 1944, the famous American paleontologist George Gaylord Simpson put forward a contradictory view in his classic book "The Rhythm and Pattern of Evolution".
Simpson believes that rapid evolution can lead to instability and extinction, and slow evolution can lead to higher biodiversity.
This used to be a challenging point of view.
Recently, however, several researchers from the School of Earth Sciences at the University of Bristol in the United Kingdom published a study in the internationally renowned journal "Palaeontology", which confirmed by investigating scaly species including lizards and snakes and some of their close relatives. Simpson's early views.
Their research confirms that some branches of biology evolve quickly and become extinct.
What determines the speed of species evolution
What is the power to drive evolution?
Darwin once answered this question.
Expressed in modern discourse, the basic mode of evolution is that the frequency of occurrence of the configuration of genes and chromosomes within the ethnic group has changed.
"A gene may change the characteristics of the head, prolong lifespan, reconstruct the color and shape of wings, or create a huge population." The famous American biologist and naturalist Edward Wilson wrote in his classic book "Fun Written in "Life".
Regarding species evolution, different theories have different descriptions.
In the "Origin of Species" published in 1859, Darwin believed that in the evolution of biodiversity, many large branches seem to have emerged through rapid evolution, while smaller groups have undergone slow evolution.
"Traditional Darwinian evolution theory believes that biological evolution is gradual, that is, changes in biological morphology are gradual and cumulative. The discontinuous equilibrium theory believes that biological changes tend to be conservative within a certain range of environmental conditions, and changes are sudden and explosive. Therefore, organisms remain unchanged for a period of time, but will suddenly change in a relatively short period of time." Dong Liping, an associate researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, introduced to a reporter from Science and Technology Daily that in the history of biological evolution , We observe both gradual changes and sudden changes.
Simpson was a paleontologist active in the United States from the 1940s to the 1980s. He is famous for his understanding and contributions to the theory of evolution and the intercontinental migration of animal species.
In his research, Simpson examined the basic mode of evolution within the framework of Darwin's theory of evolution, and observed that many rapidly evolving species belong to unstable groups, and they may adapt to rapidly changing environments.
In 1944, he proposed in the classic "The Rhythm and Pattern of Evolution" that high evolution speed is unlikely to last for a long time, because fast-evolving clades may be so unstable that they may become extinct or have a slower evolutionary speed. Species.
So, how do we measure the rate of biological evolution, and how to define a new trait and taxa?
Dong Liping introduced that the evolution rate of organisms is the change of organisms within a branch within a unit time.
Changes can be molecular, such as the number of changes in DNA base pairs per unit time; it can also be morphological, such as the number of changes in morphological characteristics and traits per unit time.
For the branches with a large number of changes in the same time period, we say that their evolution rate is fast.
"In biology, traits are identifiable morphological characteristics. A new taxa is defined by traits that are shared by this taxa and are different from other taxa," said Dong Liping.
However, due to the unavailability of research materials such as fossils and the influence of factors such as research methods and models, paleontologists have long identified the "early burst" model as the best explanation for the expansion of many clades. It is rare to empirically test Simpson’s hypothesis.
Until the emergence of research by Dr. Herrera Flores from the University of Bristol.
Research on the scale dragon model leads to an accident
Squamatosaurus is a super branch of reptiles, including scaly composed of lizards and snakes, as well as proboscis represented by lizards.
Among them, there are about 10,000 species of squamous animals. They have different forms and ecology. They can be found in water, land and air habitats all over the world, from the tiny chameleon the size of a thumb in Madagascar to the 10-meter-long python, and the same huge extinct ones. The marine mosasaurs are all scaly species, and they mostly feed on seaweed, plants, insects and mammals.
In contrast, the proboscis has long been declining, and today only a single species-the lizard has survived, and it is geographically restricted to a part of the New Zealand island.
The "relatives" of the same scale dragons, why are their fates so different?
In fact, the existing biodiversity of scale dragons is just a microcosm of their long evolutionary history.
Before conducting research on the evolutionary speed of scaly dragons, Dr. Herrera Flores and others were expecting to find traces of slow evolution in rosacea animals, and traces of rapid evolution in scaly animals.
However, through a series of studies on 167 species of Mesozoic scale dragons, they observed the opposite situation.
Dr. Herrera Flores said that scale dragons originated in the early Mesozoic era 250 million years ago, and they differentiated into scales and rosacea.
They found that in the first two-thirds of the evolutionary history of scales, the rate of evolution was slow; while its sister evolutionary branch, the Procyon, which is now composed of only one species, has shown a rapid rate of evolution.
Various research evidences indicate that in the early evolution of the squamosaurus, the rosacea was a more successful and diversified group, while the diversity of the earliest scaly animals was much less.
Until the Cretaceous, the number of rosacea animals declined, but squamous animals experienced a lot of radiation, including morphological and phylogenetic expansion.
That is to say, in the Cenozoic, squamous animals such as lizards and snakes are still important parts of the terrestrial ecosystem, but the proboscis has been reduced to the "only remaining" relic species such as the wedge-toothed lizard.
"The faster the evolution, the faster the extinction" or not universal
After the extinction of the dinosaurs 66 million years ago, both the rosacea and the squamous animals suffered heavy losses, but the number of squamous species was later restored. Today, more than 10,000 species survive and have evolved at a rapid rate. Generally faster.
This conclusion provides an example for Simpson's challenging point of view, confirming that rapidly evolving groups of organisms are not necessarily more prosperous in the modern life world.
Just like the tortoises and rabbits racing in the ancient "Aesop's Fables", compared with the proboscis, the scales have the slow evolution rate of the tortoise, but this means a low level of volatility and less risk of extinction.
However, Dong Liping believes that there are significant differences in the evolution rate of different groups of organisms.
As shown in this new study by Herrera Flores and others in Paleontology, the proboscis and scaly like lizards and snakes, both of which are squamatosaurus, have significantly different evolution rates. In the Mesozoic Era, the evolution rate of rosacea was significantly faster than that of scaly.
At the same time, the evolution rate of the same group in different time periods is different. For example, the evolution rate of the body size of the rosacea and the scaly is higher in the Cretaceous than in the Jurassic.
"The heterogeneity of the evolution rate of different groups of organisms and different time periods is widespread in organisms, but the mechanism of the heterogeneity is still unclear. It may be related to its own genetic and morphological characteristics, but it is also related to other organisms and survival. Environment related." Dong Liping said.
In fact, previous paleontologists’ research results on the morphological evolution of dinosaurs, ray-finned fish, crocodiles and crustaceans have linked the success of evolutionary branches to the rapid evolution speed.
Most other quantitative studies have shown that rapid evolution is the key to long-term success, but the opposite is true for scale dragons.
"Therefore, the phenomenon of'the faster the evolution, the faster the extinction' is not universal. There are also rapidly evolving and very prosperous biological groups in the modern life world, such as the above-mentioned radial fish. It has not yet been possible. Whether it is determined whether the rate of evolution is directly related to whether a taxa can survive in the end, and the factors that control the rate of evolution of a taxa are still unclear." Dong Liping said.