The cause of mollusk decline on the Ogasawara Islands |
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Authors: | Isamu Okochi Hiroki Sato Takashi Ohbayashi |
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Affiliation: | (1) Department of Forest Entomology, Forestry and Forest Products Research Institute, P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki, 305-8687, Japan;(2) Agricultural Pest Division, Ogasawara Subtropical Branch of Tokyo Metropolitan Agricultural Experiment Station, Chichijima-Is., Ogasawara, Tokyo, 100-2101, Japan |
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Abstract: | Decline of land snails on the Ogasawara Islands was studied. In Hahajima, major alien predators such as Euglandina rosea and Platydemus manokwari are not present, but some small endemic snails, for example, Hirasea spp. and Ogasawarana spp., are already rare and more common endemic snails, for example, Mandarina spp., are also declining in the northern mountains. The decline cannot be directly explained by forest deforestation and by its subsequent regeneration. Three species of flatworms were found to eat small snails under captive conditions. The distribution of these flatworms is restricted to the northern mountains of Hahajima where Mandarina is declining and its survival is low. These predators are plausible candidates as a cause of the decline of the endemic snails. |
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Keywords: | Decline Flatworm Island Land snail Mandarina Mollusk Ogasawara Islands Predator |
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