If one day you open the door and find yourself surrounded by spiders...

In recent years, there have been endless reports about invasive species in China, and the top two in the popularity ranking are definitely occupied by insects, with the red fire ant and the gypsy moth occupying all the headlines.

In addition, giant African snails, crayfish (Procambarus clarkii), bullfrogs, red-eared sliders, Spartina alterniflora, water hyacinth... are also typical representatives of invasive species in my country. Through "unremitting efforts", they have successfully occupied the high ground in my country, and some of them have even been served on the dining table (food is indeed the first necessity of the people).

Of course, it is not only my country that is vulnerable to invasive species. Other countries have the same troubles, such as the "garden exotic pet" that has been plaguing the American people for nearly seven years - the clavata (Trichonephila clavata).

Does it look familiar? Nephila clavata is a very common spider in Beijing. Image source: Tadpole Jun

The body of the Nephila clavata is brightly colored, with a dark brown head and thorax, goose yellow and silver-white stripes on the back of the abdomen, and two goose yellow patterns on the ventral surface; the spindles are bright red, and the feet have black and yellow rings. The female spider can be up to 20-25 mm long, while the male spider is only 1/4 of the female spider's length. They were originally a type of spider distributed in China, India, Japan and other places. Why did they appear in the United States on the other side of the earth?

A female spider with a big belly. Image source: Wikipedia

As early as 2015, researchers discovered the first Nephila clavata in northeast Atlanta, but due to the small number, it did not attract people's attention. In the next 5-6 years, they quietly expanded their territory under the noses of Americans. By the end of last year, the number of Nephila clavata in the United States had reached millions. Recently, a new study published in "Physiological Entomology" showed that Nephila clavata is likely to not be hindered in the process of spreading, and they may reproduce and thrive in most parts of the United States, obtain a "green card", and settle permanently.

Look at this expansion. Image source: "Physiological evaluation of newly invasive jorō spiders (Trichonephila clavata) in the southeastern USA compared to their naturalized cousin, Trichonephila clavipes"

Their "masterpieces" are posted everywhere, on wires, in gardens, on trees, and even on residents' doors. Their strong web-making ability is a headache for locals. Local residents say they are fed up with these spiders weaving webs everywhere. If they are not careful, their bodies and hair will get stuck with spider webs, which is especially uncomfortable for those who are "spiders".

Pictures speak louder than words, Image source: Wikipedia

However, the expansion journey of the club-leaved astilbe has not ended. The club-leaved astilbe has a strong ability to survive and can adapt to the climate of the east coast of the United States. In addition, it lacks natural enemies and spreads very quickly.

However, researchers also said that there is no need to worry too much about this. Although they are colorful and entangled in a large web, they look very scary. However, they are actually not very aggressive and toxic. They generally do not actively "provoke" humans, so they do not pose much threat to humans.

Image source: Wikipedia

Why did the clavate astilbe suddenly appear on the east coast of the United States when it was living well in its original distribution area? This has to do with the reasons for the invasion of species.

If a species is introduced naturally or artificially into an area where it did not previously exist naturally, and is capable of developing to a certain number there without further human intervention, thus threatening the local biodiversity and becoming a local nuisance, it can be called an "invasive species."

Generally speaking, natural spreads such as wind, water, insects or birds invade. Human introduction usually occurs through human transportation such as ships, international trade logistics or marine debris, engineering construction, etc. It is very likely that the clavate Broom came to the United States through international trade, and it was unexpected that it would stay there permanently.

In recent years, with the rapid development of human transportation and the advancement of international logistics, human activities have become the main cause of species invasion. Due to the lack of attention paid to the invasion of alien species in some countries and regions, poor management and imperfect legislation, species invasion incidents occur frequently.

Water hyacinth (Eichhornia crassipes), a well-known invasive species in China, Image source: Tadpole Jun

The invasion of alien species may threaten the ecological environment and native species of the invaded area. When alien species successfully invade, the composition and structure of the ecosystem will change first. Due to the lack of natural enemies, alien species will reproduce rapidly in a short period of time, occupy the ecological niches of other species, and form a competitive relationship with native species in terms of food and space, which is likely to lead to a reduction in species diversity in the invaded area.

A red-eared turtle released by humans. Image source: Tadpole Jun

Due to the over-reproduction of some alien species, human production and life will be affected to a certain extent, and even cause economic losses. In addition, alien species may also endanger human health. For example, ragweed, which is native to North America, grows on a large scale after invading China, and its pollen can cause allergic reactions in some people.

The larvae of the American white moth are eating leaves. Image source: Tadpole Jun

However, it is still unknown whether the Astilbe will have an impact on the American ecosystem. There is no evidence that the Astilbe will destroy the local ecological balance or threaten the survival of other native species. Therefore, American agricultural agencies and ecologists recommend "try not to kill them."

What invasive species have you seen in your life? Please leave a message below to tell us.

References:

1. Davis, AK &Frick, BL (2022) Physiological evaluation of newly invasive jorō spiders(Trichonephila clavata) in the southeastern USA compared to their naturalized cousin, Trichonephila clavipes. Physiological Entomology, 1– 6. Available from: https://doi.org/10.1111/phen.12385

2. Wang Guanyu, Yu Xiaodong, Yao Weizhi. Research on the causes and countermeasures of alien species invasion in my country[J]. Ecological Economy, 2006(5):272-275,296.DOI:10.3969/j.issn.1671-4407.2006.05.078.

3. The invasive harm and prevention measures of alien plant species[J]. Journal of Zaozhuang University, 2005, 22(5): 52-57. DOI:10.3969/j.issn.1004-7077.2005.05.014.

4. Gao Jianliang, Zhao Linyan, Zhao Linfeng. A preliminary study on the harm and control strategies of alien invasive species in my country[J]. Hunan Forestry Science and Technology, 2005, 32(6): 72-75. DOI: 10.3969/j.issn.1003-5710.2005.06.023.

Review expert: He Jiale, project officer of WWF Northeast Resident Working Group.

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