Ginkgo biloba is endangered? Aren’t they everywhere on the streets?

Ginkgo biloba is endangered? Aren’t they everywhere on the streets?

媪媪果壳自然2023-10-30 12:00 Published in Sichuan

Ginkgo and Metasequoia are probably the most well-known endangered plants - of course you may not know that they are endangered.

"This thing is everywhere in our area, why is it endangered?"

The endangered here refers to the survival status of these plants in the wild environment, and does not include the trees planted in your streets and communities.

Metasequoia and Ginkgo｜Paulitzer & Ellery / wikimedia

Nursery-grown varieties are almost completely different from plants that grow naturally in the wild:

On the one hand, in order to facilitate gardening management or uniformity, the plants we cultivate must be highly uniform, that is, each tree is similar, and the same family is selected for breeding and seedling cultivation, and even excellent plants are propagated asexually . This means that the ginkgo trees you see on the streets may all be sisters from the same mother, or even the incarnations of the same Monkey King.

On the other hand, humans can adapt cultivated varieties to various environmental climates and create suitable growth conditions for them through hybridization, breeding, genetic modification and other means. Wild populations not only do not have such preferential treatment , but sometimes luck will also determine whether their future is bright or dark.

Today, let’s talk about luck from an “idealistic” perspective.

Prehistoric relics close to us

Metasequoia

The metasequoia (Metasequoia glyptostroboides) is the only living species of the genus Metasequoia in the subfamily Sequoioideae of the family Cupressaceae.

Sequoiae is an extremely ancient group and was once an important component of the forest vegetation in the Northern Hemisphere. However, later, due to geological changes, climate change and other reasons, a large number of groups in the Sequoiae became extinct: the global temperature drop in the Neogene (when the forms of animals and plants began to approach those of modern ones) forced the Sequoiae to gradually withdraw from high-latitude areas; the drastic deterioration of the glacial climate in the Quaternary (from about 2.6 million years ago to the present, when plate movement is no longer as intense as before) caused the distribution area of ​​the Sequoiae to retreat further to middle and low latitudes, and finally disappeared completely in Europe, leaving only traces in the hinterland of East Asia and western North America.

Currently, there are only three single genera in the Sequoia subfamily: Metasequoia, Giant Sequoia and Sequoia, and each genus has only one single seedling left .

Among them, giant sequoia and North American redwood are the "giants" of the tree world. | Alpsdake & Mike Murphy / wikimedia; Bernt Rostad / Flickr

About 10 million years ago, the continuous uplift of the Himalayas caused the southeast monsoon to continue to strengthen, and the Metasequoia forests in Yunnan lost their shelter. The distribution area of ​​wild Metasequoia shrunk again, and now it is only huddled at the junction of several counties in Hunan, Hubei and Chongqing provinces and one city in China.

Metasequoia forest｜Fxqf / wikimedia

ginkgo

Ginkgo biloba is the only surviving plant of the Ginkgoales. The earliest fossils of the Ginkgoales can be traced back to 270 million years ago. According to fossil evidence, the Ginkgoales once had five families, widely distributed on all continents of the world. When angiosperms rose rapidly in the Cretaceous period, the Ginkgos also declined rapidly like other gymnosperms; after the Late Cretaceous, Ginkgo plants other than the Ginkgoaceae have basically become extinct .

During the Oligocene, due to the drop in temperature, Ginkgo continued to migrate southward; since the middle Pleistocene (580,000 to 140,000 years ago), Ginkgo has retreated again and again after experiencing multiple ice ages. Now there are only three wild populations in eastern China (represented by Tianmu Mountain in Zhejiang), southwestern China (Wuchuan in Guizhou and Jinfo Mountain in Chongqing) and southern China (Nanxiong in Guangdong and Xing'an in Guangxi).

Ginkgo leaves tell prehistoric stories | James Field; Joe Schneid, Louisville, Kentucky

fir

Another similar example is the Abies. The genus Abies was once an important tree species in the subtropical and temperate forests of the Northern Hemisphere. Abies have straight trunks, long lifespans, and are shade-tolerant and cold-tolerant. They are a group that prospered and declined with global climate change. As the temperature continued to rise during the interglacial period, and Abies are naturally afraid of heat , there were only two ways to retreat - north and upward. Whether it was rising in latitude or in altitude , it was like drinking poison to quench thirst. Although it brought a short period of comfortable coolness, it also meant that the Abies would have no way to retreat.

During the Ice Age, some of the Abies species that once spread to the edge of the tropics chose to retreat northwards, returning to temperate and boreal forests, while others retreated to the top of the mountains. The famous Abies beshanzuensis is the latter.

Baishanzu fir grows in the valleys of Baishanzu main peak at an altitude of 1,700 meters in Lishui, Zhejiang, and now only a handful of them remain. Similarly, Fanjingshan fir is only distributed on the steep slopes of Fanjingshan ridge at the junction of Jiangkou, Songtao and Yinjiang counties in Guizhou; and Yuanbaoshan fir is only distributed in the mixed coniferous and broad-leaved forests at an altitude of 1,700 to 2,050 meters in Yuanbaoshan, Rongshui County, Guangxi.

Stamps featuring Baishanzu Fir｜China Post

These firs, which are intermittently distributed on the hills of the south, are both the "old people" of the glacial period that are incompatible with the interglacial period and the snow babies in the warm spring. As the temperature rises, they can only keep climbing to the top of the mountain - if one day, even the top of the mountain becomes too hot to bear, then they will disappear forever like their relatives and friends.

Lucky or unlucky?

Endangered gymnosperms such as Metasequoia, Ginkgo, and Abies baishanzu, and even "living fossil" species such as horseshoe crabs and coelacanths, are still considered lucky ones in evolutionary events compared to their extinct relatives.

Every tiny bit of natural selection may lead to genetic drift, or even cause the population to fall into a bottleneck effect. When the number of individuals of a species is very small, an accident may cause all of them to become extinct . In fact, similar random losses have been happening all the time. The genes of lucky individuals will be passed down forever, while those with bad luck will be lost in the torrent of history. Natural selection is as plain to nature as spring flowers, autumn moon, cool breeze and flowing water.

Using small balls to simulate the effects of genetic drift, after five generations, the genes represented by the red balls have completely disappeared｜Gringer / wikimedia

The unlucky one who is closer to our lives is the banana. Nowadays, almost all bananas that can be bought in supermarkets are Cavendish bananas. Before the 1950s, the most popular banana variety in the world was the Gros Michel banana, which tasted better and was easier to store and transport. Many people may know the legendary "banana AIDS", a banana wilt disease caused by soil-borne Fusarium wilt, which almost wiped out the Gros Michel banana.

Since the cultivation of commercial bananas (triploid varieties of Musa acuminata) mainly relies on asexual reproduction , this means that thousands of bananas may essentially be the same banana: the advantage is that the traits are stable, sweetness, size, and yield are all stable; the disadvantage also comes from stability. Once a certain pathogen can infect a banana plant, large quantities of bananas will be in trouble .

A little-known fact is that the unique "artificial banana" smell of foods such as banana milk is more like Big Mac｜pixabay

With bananas as a "lesson", people dare not slack off when it comes to other cash crops.

In fact, our food is much more vulnerable than we are. The cultivation of insect-resistant and disease-resistant varieties of cash crops has always been a hot topic in the global biological community.

Soybean (Glycine max) is an important crop that is plagued by pests and diseases. Its close relative, wild soybean (G. soja), a national second-level protected plant, can provide protection. Wild soybeans are widely distributed, have a large population, and have variable traits. If cultivated soybeans are threatened by certain pests and diseases and their yields drop sharply, we can still rely on hybridization, genetic modification, and other means to keep the cultivated soybean population going.

Pests and diseases originate from nature. Wild soybean populations that survive in the wild environment will always find ways to resist difficult disasters. However, if only cultivated soybeans are left in the world and there are no wild soybeans, they will be powerless to resist when they encounter diseases.

Soybeans, old soybeans. Behind everything that seems ordinary, there may be many unknown stories｜public domain

Even if taking responsibility is counterintuitive

Compared with agriculture, forestry seems to be further away from urban life. In fact, the selection range of urban roadside tree species is extremely narrow, and ginkgo and metasequoia happen to be among them. It also happens that their ancestors were once widely distributed in the northern hemisphere , so it is not difficult for artificially cultivated varieties to return to the land where their ancestors once set foot. This creates the illusion that "the streets are full of trees" .

However, the widespread use of mature varieties/lines can bring hidden dangers, and the worst result can be seen in bananas. In times of crisis, the rich gene pool preserved by wild populations may be able to save the street trees that are pampered in cities .

Ginkgo Avenue｜pixabay

The Metasequoia glyptostroboides planted in the nursery yard has not produced any seedlings in the wild for decades, which means that they are already powerless in the natural competition and can hardly compete with the thriving angiosperms. Without human help, the living fossils that have only been revived for a hundred years may disappear again . There is an abyss in front of them, but we can reach out a hand.

Plants have a strong ability to reproduce. Even if they only rely on a branch cutting or grafting, they can grow a new individual - of course, the genes of this new individual are exactly the same as the mother plant. If we only keep cultivated varieties and lose wild populations, we will lose a lot of genetic information of plants . When we have this genetic information, we can explore one of the three major "philosophical" questions: Where does life come from?

Exploring where each species comes from is not just about satisfying curiosity and answering philosophical questions.

Currently, almost all of the cultivated ginkgo trees in the world originate from the Tianmu Mountain population in Zhejiang. If breeders want to take precautions and take precautions, they can hybridize plants from Chongqing or Guangxi to obtain varieties with better traits and stronger resistance to adversities - and this is just the visible benefit of wild populations.

Wild populations can help us understand the interactions between organisms . Wild soybeans are creeping and climbing, with slender and weak stems, small seeds and low oil content. How can they resist drought and flood, insect diseases without human care? Who does their stems entwine with? Who does it rely on for pollination and shade? Who does its seeds feed and under whose protection does it grow year after year? Who does it live with and who does it die with? These are all practical and important studies. If there is any practical significance, at least understanding wild soybeans can help soybeans closer to us overcome some possible difficulties .

The connection between plants and trees is far more complex and important than we think｜pixabay

Humans have almost forgotten how to live in harmony with their neighbors. Those who have just come to their senses are even more confused: how do these plants, insects, and animals, who share the sun, rain, warmth, cold, and wetness, coexist in harmony?

The complexity and diversity of communities and ecosystems mean that there are no two identical ecosystems in the world. Uncontrolled and unrepeatable attempts are even more confusing - we don't know how these neighbors have spent tens of millions of years together, nor do we know how our ancestors spent their time. Therefore, after destroying the original ecological environment, we don't know how to restore it to its original state.

We will all continue to live on this planet for the foreseeable future.

Although protecting wild populations of species is a long and arduous task, and may be incomprehensible to most people, it is ultimately for the sake of humanity itself.

Author: 媗媗

This article comes from GuokrNature (ID: GuokrNature)