Influence of global warming on geographical cline of elytral colour polymorphism in the ladybird beetle, Harmonia axyrids

自然选择在解释生物体的适应性进化中起着核心的重要作用。然而，与家养动植物的人工选择的许多丰硕成果相比，支持自然选择作用的实地证据很少。在这项研究中，我调查了地理渐变和它的变化几十年来的鞘翅颜色多态性的瓢虫，异色瓢虫，在日本。近几十年来，在本屿、四国岛和九州岛的大部分采样点，黑素基因的频率增加，而非黑素基因的频率下降。观察到的基因频率的变化与生殖季节的温度在大多数气象站接近采样地点的增加。这些结果可能是自然选择作用下微进化的现场证据。

Natural selection has played a central importance in the explanation of adaptive evolution in organism. 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 elytral colour polymorphism of the ladybird beetle,Harmonia axyrids, in Japan. In most of the sampling locations in Honsyu, Shikoku and Kyusyu islands, the frequencies of melanic genes increased, while the frequency of non-melanic gene decreased during the last several decades. The observed change in the gene frequencies coincided with the increase in the temperature in the reproductive season at most meteorological stations close to the sampling locations. These results could be a field evidence of micro-evolution by natural selection.