Ginkgo biloba: a living fossil that can be seen and touched

Autumn is the most beautiful season of the year for ginkgo trees. The trees are full of golden leaves, which fall with the wind like golden butterflies flying in the sky, and finally turn the ground into a golden color.

It is as beautiful and lively as a girl, and its beauty actually began more than 200 million years ago and has continued to this day.

Guo Moruo described it in his essay "Ginkgo" as follows: "Most people don't know that you are the most ancient and advanced of flowering plants, that your pollen and ovules have animal-like sexual characteristics, and that you are a rare treasure preserved entirely by human efforts."

According to fossil data found around the world, the evolution of ginkgo has roughly gone through three major geological periods:

✦ Born in the Paleozoic Era. According to fossils, the origin of ginkgo is about 225 million to 600 million years ago. Soon after gymnosperms appeared on Earth, they gradually began to decline. Most gymnosperms began to die out. Only a small number of gymnosperms such as ginkgo and conifers that can adapt to terrestrial conditions survived.

✦ Prospered in the Mesozoic Era. In the Jurassic period of the Mesozoic Era (135 million to 180 million years ago), the climate and environment on Earth tended to be arid, which was suitable for the mass reproduction, development and differentiation of Ginkgoes. At that time, Ginkgoales plants existed almost everywhere in the world except the equator and Antarctica.

✦ Declined in the Cenozoic Era. In the late Cretaceous period of the Cenozoic Era (70 million to 135 million years ago), the Earth's climate changed dramatically and was no longer suitable for the survival of gymnosperms. Ginkgo plants began to decline and were gradually replaced by highly evolved and widely adaptable angiosperms.

Subsequent glacial movement led to the extinction of all ginkgo plants in North America, Europe and other parts of the world, and ginkgo in the Asian continent is also on the verge of extinction.

Fortunately, since most of China's mountains run in an east-west direction, some mountains have escaped the invasion of glaciers, allowing a limited number of ginkgo trees to survive in our country and multiply to this day. Therefore, ginkgo trees all over the world today originated in China.

For a long time, the evolution of ginkgo has aroused great interest among scientists and has been studied in depth.

In October this year, a collaborative team consisting of Zhejiang University, the Institute of Botany, Chinese Academy of Sciences and the Beijing Genomics Institute in Qingdao spent five years completing the first draft of the ginkgo genome. After that, they resequenced the genomes of 545 ginkgo individual samples from around the world and built the largest ginkgo genetic database to date. This provides important information for understanding the evolutionary history and evolutionary potential of ginkgo, and provides a comprehensive evolutionary framework for the research and protection of ginkgo.

The 545 representative ginkgo samples collected come from 51 populations, covering almost all locations where ginkgo grows on Earth. The ginkgo genome size exceeds 10Gb, which is 3.4 times that of humans. The 545 ginkgo trees generated a total of 44Tb of massive data.

Analysis of the data revealed that the collected samples could all be traced back to China and were divided into four main populations: southwest, south, east and north of China.

The southwest, south and east are the three glacial "refuges" of Ginkgo, and four ancient genetic components of Ginkgo have been detected.

The so-called refuge means that when the world experiences extreme climate, the traces of species will gradually shrink to a certain area. When the climate improves, they will spread and grow outside the area again.

As the global climate continues to change, the shapes of many animals and plants have undergone tremendous changes, and some have even become extinct because they cannot adapt to the new environment. However, the shape of ginkgo has been able to remain stable for more than 200 million years, which has always been surprising.

In fact, for a "living fossil" like Ginkgo, low morphological variation does not mean low genetic diversity. Maintaining its morphological stability may be an effective adaptation strategy to cope with environmental changes.

How ginkgo was introduced from China to different countries on various continents is also a long-standing issue of concern.

According to previous literature and books, it is speculated that there are two ways for ginkgo to be introduced to foreign countries: one is that from the Northern and Southern Dynasties to the Sui and Tang Dynasties, ginkgo was introduced to the Korean Peninsula by land, and then from the Korean Peninsula to Japan by sea;

Another way is that during the heyday of the Tang Dynasty, Japanese envoys and monks introduced ginkgo from my country to Japan by sea. In the 18th century, Europeans introduced ginkgo from Japan, and later, Americans introduced it to America from Europe.

However, the latest research shows that ginkgo trees in Europe and the United States were introduced from eastern China many times, which denies the possibility that European ginkgo originated in Japan or South Korea. At the same time, it also confirms that Chinese ginkgo was introduced to Japan and North Korea earlier than Europe and the United States.

Regarding “living fossils”, whether they are disappearing is another intriguing question.

For example, the giant panda was long considered an evolutionary dead end, but it has proven to be a successful species, highly adaptable to changes in its environment.

Although studies have shown that ginkgo maintains a high level of genetic variation, this also means that ginkgo has more coping strategies when faced with drastic environmental changes.

However, researchers conducting field surveys have found that there have been no naturally regenerated saplings or surviving seedlings over three years around many wild ginkgo trees for nearly a decade, and most wild ginkgo populations are not in nature reserves. They need people to lend a helping hand and give them more attention.

In this rapidly changing era, things with more history and stories tend to be more precious. The ginkgo, which has a history of more than 200 million years, is even more worthy of cherishing.