| Budget Amount *help |
¥2,670,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥270,000)
Fiscal Year 2007: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Natural selection has played a central role in the explanation of adaptive evolution in organisms. There have been, however, very few field evidences supporting the action of natural selection, compared to many fruitful results in artificial selection of domestic plants and animals. In this study, I investigated the geographical cline and its change over decades in the lytral colour polymorphism of the ladybird beetle, Harmonia axyrids, in Japan. Geographical cline in the frequencies of melanic and non-melanic genes was remarkably observed over Honsyu, Shikoku and Kyusyu islands. It was considered that temperature in reproductive season of this beetle (April-July) could be an important factor for generating the geographical cline. In most of the sampling locations of these islands, the frequencies of melanic genes increased, while the frequency of the non-melanic gene decreased during the last several decades. Change of pattern in natural selection acting on colour polymorphism was considered to be a major cause of the change in gene frequencies. At the higher latitude, the magnitude of selection was estimated to be larger. The observed change in the gene frequencies coincided with an increase in the temperature in reproductive season at most meteorological stations close to the sampling locations. These results could be a field evidence of micro-evolution by natural selection, and suggest that global warming can affect the genetic constitution of species.
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