Small off-shore islands can serve as important refuges for endemic beetle conservation |
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Authors: | Shinji Sugiura Tomoyuki Tsuru Yuichi Yamaura Hiroshi Makihara |
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Institution: | (1) Department of Forest Entomology, Forestry and Forest Products Research Institute, Tsukuba Ibaraki, 305-8687, Japan;(2) Department of Ecology and Systematics, Graduate School of Agriculture, Hokkaido University, Sapporo Hokkaido, 060-8589, Japan |
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Abstract: | Although large islands generally support a richer insect fauna than small islands, many large islands, which are more often
inhabited, have lost numerous species because of human activities and introduced organisms. To clarify the consequences of
endemic insect conservation on small islands near inhabited islands, we compared the species richness, abundance, and composition
of two beetle groups (Coleoptera: Cerambycidae and Mordellidae) captured using Malaise traps among three islands (Chichijima,
24.0 km2; Anijima, 7.85 km2; Nishijima, 0.49 km2) in the oceanic Ogasawara (Bonin) Island group in the northwestern Pacific during June–July 2006 and 2007. Chichijima, the
largest island, is inhabited, while Anijima and Nishijima are not. The numbers of cerambycid and mordellid species previously
recorded were positively correlated with island area. However, the total numbers of cerambycid and mordellid species we captured
in Malaise traps were not correlated with island area because we were unable to collect many species previously documented
on Chichijima. The numbers of cerambycid and mordellid species per trap did not differ significantly among islands and years,
although the deviance was well explained by the island variable. We captured greater numbers of cerambycid and mordellid individuals
on Chichijima than on Anijima and Nishijima, and the numbers of cerambycid and mordellid individuals per trap significantly
differed among islands and between years. Redundancy analysis (RDA) showed that the species composition of cerambycids and
mordellids differed among the three islands. Whereas endangered species were rarely captured on Chichijima, alien or non-endemic
species were frequently collected. Cerambycid and mordellid beetles on Chichijima may have been deleteriously affected by
recent forest disturbance and introduced organisms. Therefore, conserving insect fauna on uninhabited island “refugia” is
important for preserving the insect diversity of the Ogasawara Islands. |
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Keywords: | Alien species Biodiversity Disturbance Island area Ogasawara (Bonin) Islands Species richness |
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