事例研究 CASE STUDY
深泥池における外来魚駆除事業がブルーギル個体群の遺伝的多様性に及ぼす効果について:マイクロサテライト多型解析に基づく推定
加藤 幹男1)*・真鍋 由紀2)・四反田 武志2)・安部倉 完3)・竹門 康弘4)・長澤 哲也1)・谷田 一三1)
1) 大阪府立大学大学院理学系研究科生物科学専攻 〒599-8531 堺市中区学園町1-1
2) 大阪府立大学総合科学部自然環境科学科 〒599-8531 堺市中区学園町1-1
3) 京都大学大学院理学研究科動物生態学研究室 〒606-8502 京都市左京区北白川追分町
4) 京都大学防災研究所水資源環境研究センター 〒611-0011 宇治市五ケ庄
2) Department of Earth and Life Sciences, College of Integrated Arts and Sciences, Osaka Prefecture University, 1-1 Gakuencho, Sakai 599-8531, Japan
3) Laboratory of Animal Ecology, Department of Zoology, Graduate School of Sciences, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502, Japan
4) Water Resources Research Center, Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji 611-0011, Japan
Abstract: Bluegill sunfish Lepomis macrochirus is an alien species introduced from North America in 1960, and currently widespread over Japan. It is designated as an invasive fish by which many domestic aquatic animals are threatened. Every effort to exterminate the populations of L. macrochirus has been continued, since 1998, in Mizorogaike Pond at northern Kyoto City, where the whole biological community has been protected as a natural monument of Japan. Capturing individuals (since 1998) and destroying spowning redds (since 2002) greatly decreased the population size in the pond: the estimated population size in 2005 was about one tenth of 1998. In that regard, we evaluate the changes in genetic structure caused by this rapid reduction of population size by using microsatellite polymorphisms. A microsatellite BG6X locus has shown that the genetic structure of the Mizorogaike population of 2006 was in Hardy-Weinberg equilibrium, but that of 2007 deviated from the equilibrium. Also, allelic richness decreased in 2007. According to the size frequency distribution, the specimens from Mizorogaike in 2006 were expected to have been born in the years of 2003 or earlier, while those of Mizorogaike in 2007 were expected to have been born in 2003-2005 when the destruction of spawning redds had been successfully performed. The results suggest that the majority of the Mizorogaike population in 2007 were originated from the small number of spawning redds that were escaped from the population control, and it caused the deviation from Hardy-Weinberg equilibrium.
Key words: bluegill sunfish, microsatellite, Mizorogaike, polymorphism, population control
摘要
深泥池水生生物研究会が行っている外来魚駆除事業の継続的実施によって,深泥池における2005年のブルーギルの個体数は駆除事業開始時の1998年に比べておよそ10分の1まで減少した.この人為的な個体群抑制が,深泥池ブルーギル個体群の遺伝的構造に及ぼす効果を見積もるために,マイクロサテライト座位BG6Xの多型(CA繰返し数多型)を指標として,その対立遺伝子構成を2006年の試料と2007年の試料とを用いて比較解析した.その結果,2007年の試料では,遺伝子型頻度がハ-ディー・ワインバーグ平衡からずれていた.さらに,集団内対立遺伝子数の期待値(Allelic richness)は,2006年から2007年にかけて顕著な減少傾向を示した.これらのことは,試料個体が生まれたと推定される期間に行われた産卵床の破壊が,個体群の繁殖阻止に加えて対立遺伝子構成にも大きく影響を及ぼしていることを示唆する.
2008年3月21日受付, 2009年12月30日受理* e-mail: mkato@b.s.osakafu-u.ac.jp
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