The effects of native species community on spread of invasive species by comparisons of original and remote populations.

本研究以入侵瓢虫为研究对象，通过野外和室内研究，探讨了入侵瓢虫在北美的建立和扩散机制，特别是入侵瓢虫与天敌及原生瓢虫的相互作用，如：（1）七星瓢虫和异色瓢虫对北美原生瓢虫的影响;（2）二斑瓢虫与日本原生瓢虫的相互作用;（3）Olla v-nigrum与日本本地物种的相互作用;（4）食草瓢虫Epilachna varivestis在原种群（危地马拉）和偏远种群（日本）中的死亡因素。还预测了入侵物种的可能命运。在（1）中，异色瓢虫与北美的本地物种相比，具有相对的攻击性和多面手，这表明与异色瓢虫共享栖息地的本地物种的丰度下降是由于异色瓢虫的内团捕食。此外，异色瓢虫可能在北美和欧洲进一步传播。在（2）中，双斑圆腹蛛与异色瓢虫（日本本土物种）共享栖息地，并且经常遭受异色瓢虫的群体内捕食，这表明双斑圆腹蛛在日本的进一步传播是不可能的。在（3）中，日本本地种六斑唇鱼可能是入侵种龙葵的猎物和栖息地资源的竞争者。然而，相当低丰度的M.sexmaculatus表明，O.v-nigrum的传播取决于其猎物的分布，Heteropsylla cubana，也是入侵物种，并在日本迅速蔓延。也就是说，O.v-nigrum在日本琉球群岛的进一步传播是可能的。在（4）中，在日本，变叶真绥螨经常被一种本地寄生蜂寄生，这种寄生蜂有效地调节了变叶真绥螨的丰度和传播，这表明它不太可能在日本迅速传播。

A series of field and laboratory studies using invasive species of ladybird was conducted for understanding of mechanisms that enable those to establish and spread, especially their interactions with natural enemies and native ladybird species in original and remote area, such as (1) The effects of Coccinella septempunctata and Harmonia axyridis on native species in North America, (2) Interaction Adalia bipunctata with native species in Japan, (3) Interactions Olla v-nigrum with native species in Japan, and (4) Mortality factors of herbivore ladybird, Epilachna varivestis, in original (Guatemala) and remote populations (Japan). Possible fate of invasive species is also predicted. In (1), H.axyridis is relatively aggressive and generalist compared with native species in North America, suggesting that decrease in abundance of those natives, which share habitat with H.axyridis, due to intraguild predation by H.axyridis. In addition, further spread of H.axyridis in North America and Europe is likely. In (2), A.bipunctata share the habitat with H.axyridis, native species in Japan, and often suffer from intraguild predation by H.axyridis, suggesting that further spread of A.bipunctatat in Japan is unlikely. In (3), Menochilus sexmaculatus, a native species of Japan, can be a possible competitor of invasive O.v-nigrum for prey and habitat resources. However, considerably low abundance of M.sexmaculatus suggests that spread of O.v-nigrum depends on distribution of their prey, Heteropsylla cubana, also invasive species and rapidly spreading in Japan. That is, further spread of O.v-nigrum in Ryukyu Islands, Japan, is likely. In (4), in Japan, E.varivestis is often parasitized by a native parasitoid wasp, which efficiently regulates abundance and spread of E.varivesti, suggesting that its rapid spread in Japan, is unlikely.