Shinobe Shotaro, Uchida Shota, Mori Hideaki, Okochi Isamu, Chiba Satoshi
Graduate School of Life Science & Center for Northeast Asian Studies, Tohoku University, 41 Kawauchi, Aoba-ku, Sendai, Miyagi, 980-8576, Japan.
Japan Wildlife Research Center, 3-3-7, Kotobashi, Sumida, Tokyo, 130-8606, Japan.
Sci Rep. 2017 Sep 29;7(1):12400. doi: 10.1038/s41598-017-12653-4.
Invasive non-native species are of great concern throughout the world. Potential severity of the impacts of non-native species is assessed for effective conservation managements. However, such risk assessment is often difficult, and underestimating possible harm can cause substantial issues. Here, we document catastrophic decline of a soil ecosystem in the Ogasawara Islands, a UNESCO World Heritage site, due to predation by non-native land nemertine Geonemertes pelaensis of which harm has been previously unnoticed. This nemertine is widely distributed in tropical regions, and no study has shown that it feeds on arthropods. However, we experimentally confirmed that G. pelaensis predates various arthropod groups. Soil fauna of Ogasawara was originally dominated by isopods and amphipods, but our surveys in the southern parts of Hahajima Island showed that these became extremely scarce in the areas invaded by G. pelaensis. Carnivorous arthropods decreased by indirect effects of its predation. Radical decline of soil arthropods since the 1980s on Chichijima Island was also caused by G. pelaensis and was first recorded in 1981. Thus, the soil ecosystem was already seriously damaged in Ogasawara by the nemertine. The present findings raise an issue and limitation in recognizing threats of non-native species.
入侵性非本地物种在全球范围内备受关注。为了进行有效的保护管理，需要评估非本地物种影响的潜在严重程度。然而，这种风险评估往往很困难，低估可能造成的危害可能会引发重大问题。在此，我们记录了联合国教科文组织世界遗产小笠原群岛土壤生态系统的灾难性衰退，这是由于此前未被注意到的非本地陆地纽形动物佩氏地纽虫的捕食所致。这种纽形动物广泛分布于热带地区，此前没有研究表明它以节肢动物为食。然而，我们通过实验证实，佩氏地纽虫会捕食各种节肢动物类群。小笠原的土壤动物群原本以等足类动物和双足类动物为主，但我们在母岛南部的调查显示，在被佩氏地纽虫入侵的地区，这些动物变得极为稀少。食肉节肢动物因其捕食的间接影响而减少。自20世纪80年代以来，父岛的土壤节肢动物数量急剧下降也是由佩氏地纽虫造成的，首次记录于1981年。因此，小笠原的土壤生态系统已经被这种纽形动物严重破坏。目前的研究结果揭示了在认识非本地物种威胁方面存在的一个问题和局限性。
