Cook L M, Grant B S
The Manchester Museum, University of Manchester, Manchester M13 9 PL, U.K.
Heredity (Edinb). 2000 Dec;85(Pt 6):580-5. doi: 10.1046/j.1365-2540.2000.00794.x.
Over the last three decades the frequency of the dark melanic form carbonaria of the peppered moth Biston betularia has declined in Britain. Data have been examined which show the intermediate phenotype insularia, controlled by alleles at the same locus, to have increased or remained level in frequency. Phenotype frequency of insularia does not always track allele frequency accurately because it is recessive to its alternative when carbonaria is common but dominant to the alternative when typical is common. It is shown that if insularia fitness lies between that of carbonaria and typical, and melanics replace typicals or vice versa, there will be a rise and fall in insularia allele frequency during a transitory period. The path followed is strongly affected by initial gene frequencies. During the high melanic period in Britain, differences in insularia frequency between localities may have been influenced by history of arrival of the novel morphs as well as by local selective conditions.
在过去三十年里，英国胡椒蛾（桦尺蛾）的黑化形态“碳黑型”的出现频率有所下降。已对相关数据进行了研究，结果表明，由同一基因座上的等位基因控制的中间表型“岛型”的频率有所增加或保持稳定。“岛型”的表型频率并不总是准确地跟踪等位基因频率，因为当“碳黑型”常见时它相对于另一种表型是隐性的，但当“典型型”常见时它相对于另一种表型是显性的。研究表明，如果“岛型”的适应性介于“碳黑型”和“典型型”之间，并且黑化形态取代“典型型”或反之亦然，那么在过渡时期“岛型”等位基因频率将会出现上升和下降。所遵循的确切路径受到初始基因频率的强烈影响。在英国黑化现象盛行的时期，不同地区“岛型”频率的差异可能受到新形态出现的历史以及当地选择条件的影响。
