| Research Abstract |
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.
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