Photo/Illutration A Japanese gecko (Provided by Minoru Chiba of Tohoku University)

Despite its name, the Japanese gecko, a symbol of good luck when spotted inside the home, is an alien species introduced from China around 3,000 years ago, a study shows.

Researchers from Tohoku University in Sendai came up with the finding, recently published in a U.S. science journal, through genetic analysis and paleographic studies.

They deduced that the species arrived in the Kyushu region and expanded its habitat eastward on the back of the movement of people and distribution of goods.

Japanese gecko, or nihon yamori, is the most common gecko species in Japan. 

It had long been suspected the Japanese gecko, which also inhabits eastern China, is an alien species introduced from the Asian mainland in the distant past.

The “Vocabulario da Lingoa de Iapam,” a Japanese-Portuguese dictionary compiled in 1603, contains the first known reference to yamori.

Literature from the Heian Period (794-1185) refers to tokage, which means skink in contemporary Japanese. Descriptions of the behavior of tokage led the researchers to infer the word possibly refers to gecko.

It was only in the Edo Period (1603-1867) that skinks and geckos come to be distinguished from each other, pictorially and otherwise. A piece of literature from 1697 stated that geckos inhabit western Japan but are not found in the Kanto region.

This led the researchers to hypothesize the Japanese gecko initially settled in western Japan by no later than the Heian Period before expanding geographically gradually into eastern Japan.

They analyzed the genetic information of Japanese geckos that inhabit Nanjing in China and around 40 sites in Japan.

They studied, for example, the extent of slight differences in genetic sequences to analyze how genetic diversity varied with time. Comparisons of results from different regions allowed the team members to estimate when migrations occurred.

The study indicated the Japanese gecko crossed over from the Chinese mainland to the Goto island chain of Nagasaki Prefecture around 3,000 years ago before subsequently arriving in Kyushu.

This suggests the species began expanding its habitat further eastward around 2,000 years ago, during the Yayoi Pottery Culture Period (1000 B.C.-A.D. 250), settled in the Kinki region by the end of the Heian Period, and reached the Kanto region between the late Edo Period and the early Meiji Era (1868-1912).

That scenario matched findings from the paleographic study.

The researchers noted that the routes and timings of the Japanese gecko’s migrations to different regions were closely associated with episodes of development in Japanese society.

The latter include ancient maritime transportation in the Seto Inland Sea, the building of ancient capitals, including the Heijo-kyo of Nara (710) and the Heian-kyo of Kyoto (794), the start of the Kamakura Shogunate in the late 12th century, development of the Tokaido arterial road, and development of a medieval commodity economy.

The researchers assumed the Japanese gecko migrated to Sakata, a port city in Yamagata Prefecture in northeast Japan, from the Hokuriku region by way of Kitamae-bune merchant ships.

“Japanese geckos are like a living piece of ancient literature where the history of Japanese society is engraved,” said Minoru Chiba, a graduate student of biodiversity preservation who led the study.

“Premodern activities of human society could have had bigger impact on the geographical distributions of animals and plants than we might ever imagine, although that tends to be overlooked in the shadow of what is taking place in our contemporary age,” Chiba added.

 

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