LATITUDINAL CLINE IN DROSOPHILA-MELANOGASTER FOR KNOCKDOWN RESISTANCE TO ETHANOL FUMES AND FOR RATES OF RESPONSE TO SELECTION FOR FURTHER RESISTANCE
LATITUDINAL CLINE IN DROSOPHILA-MELANOGASTER FOR KNOCKDOWN RESISTANCE TO ETHANOL FUMES AND FOR RATES OF RESPONSE TO SELECTION FOR FURTHER RESISTANCE
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DOI：
10.1111/j.1558-5646.1985.tb05666.x
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发表时间：
1985-01-01
期刊：
影响因子：
3.3
通讯作者：
GRAF, JD
中科院分区：
文献类型：
--
作者：
COHAN, FM;GRAF, JD
引入了一种用于选择果蝇以增强对极高浓度乙醇烟雾的抵抗力的装置。该装置用于快速、轻松地一次选择一千多只苍蝇，并对分布中每只苍蝇的击倒时间进行评分，同时对苍蝇造成的伤害很小。西海岸 9 个黑腹果蝇种群的样本显示出北部种群具有更高击倒抗性的显着趋势。群体的击倒抗性水平实际上与其乙醇脱氢酶（Adh）等位基因频率不相关。然后在 9 个群体中，对 5 个群体进行进一步的击倒抗性选择。每个群体被随机分为 4 组，每组 256 只果蝇：选择 2 个品系，并保留 2 个品系作为对照品系。在每一代中，对每个选择的品系进行击倒抗性测量；被击倒的最后四分之一的苍蝇被保存下来以继续选择循环。选定和未选定品系的种群规模均维持在 256。根据对前 4 代选择的反应，计算每个选定品系的已实现遗传力。这 5 个人群的遗传力估计存在显着异质性； 5 个群体的平均遗传力为 0.143 .+-。 0.019。经过 12 代，10 个选定品系的击倒时间平均增加了 2.40 倍。在选择之前，5个群体的敲低抗性是异质的；最北部居民的抵抗力最强。选择过程中击倒抗性的变化量也与纬度相关。最南端的种群将击倒时间延长了 2.23 倍；而最北部的人口则增加了 2.55 倍。经过10代选择，击倒抗性曲线为.apprx。陡度是选择前的4.5倍。因此，选择行为夸大了选择前群体之间微小的表型差异。种群间对选择反应率的差异归因于选择前存在的遗传差异。在选择过程中，Adh 频率的变化模式在群体之间和群体内都非常不一致。从Adh等位基因的变化与选择的不一致，以及选择前Adh频率和敲低抗性之间缺乏相关性，可以得出结论，Adh频率的变化不可能对所选品系的反应产生太大影响。
A device is introduced for selecting Drosophila for increased resistance to very high concentrations of ethanol fumes. This device was used to select quickly and easily over a thousand flies at a time, and score the knockdown time of every fly in the distribution, while causing very little injury to the flies. A sample of 9 west coast populations of D. melanogaster showed a significant trend toward higher knockdown resistance in more northern populations. A population''s level of knockdown resistance was virtually uncorrelated with its alcohol dehydrogenase (Adh) allele frequencies. Of the 9 populations, 5 were then subjected to selection for further knockdown resistance. Each population was divided randomly into 4 groups of 256 flies: 2 lines to be selected, and 2 lines to remain unselected as control lines. In every generation each selected line was measured for knockdown resistance; the last quartile of flies to be knocked down was saved to continue the selection cycle. Population sizes of the selected and unselected lines were all maintained at 256. Realized heritability, based on the responses to selection of the first 4 generations, was calculated for each selected line. The 5 populations were significantly heterogeneous for heritability estimates; the average heritability of the 5 populations pooled was 0.143 .+-. 0.019. Over 12 generations, the 10 selected lines increased their knockdown times by an average factor of 2.40. Before selection, the 5 populations were heterogeneous for knockdown resistance; resistance was greatest among the most northern populations. The amount of change of knockdown resistance over the course of selection was also correlated with latitude; the most southern population increased its knockdown time by a factor of 2.23; and the most northern population increased it by a factor of 2.55. After 10 generations of selection, the cline of knockdown resistance was .apprx. 4.5 times as steep as that before selection. Small phenotypic differences among populations before selection were thus exaggerated by the action of selection. The differences among populations in their rates of response to selection were attributed to genetic differences that existed before selection. The pattern of change of Adh frequencies over the course of selection was very inconsistent, both among and within populations. From this inconsistency of change of Adh alleles with selection, and the lack of correlation between Adh frequencies and knockdown resistance before selection, it was concluded that Adh frequency changes could not have had much effect on the responses of the selected lines.