Ethanol occurs naturally in the decaying fruit in which many species of Drosophila (Diptera: Drosophilidae) breed, potentially generating selection for resistance to its toxic and sedating effects. Studies measuring mortality of flies exposed to a range of ethanol concentrations have shown that within Drosophila melanogaster Meigen, populations from temperate regions are more ethanol resistant than ancestral tropical African populations. The high ethanol resistance of temperate D. melanogaster presents a puzzle, however, because breeding and feeding sites in the wild seldom contain enough ethanol to kill even more ethanol‐sensitive Afrotropical genotypes. We hypothesize that the ethanol concentrations encountered by temperate populations, though usually sub‐lethal, are nonetheless high enough to reduce fitness in other ways, potentially generating indirect selection for genotypes that can survive exposure to unnaturally high ethanol concentrations. As a first step in testing this hypothesis, we compared the effects of a sub‐lethal dose of ethanol, comparable to that obtainable from fermenting fruit, on the mating success of males from one European and one Afrotropical population. Ethanol significantly reduced mating success of males from the Afrotropical population, but had no effect on that of males from the European population. We also show that when flies are placed on medium with a realistic concentration of ethanol, considerably more ethanol is absorbed through vapor than through feeding, suggesting that courting males may be unable to avoid being exposed to ethanol. We hypothesize that the higher resistance of temperate populations to being killed by high, unnatural ethanol concentrations may have evolved in part as a correlated response to selection for behavioral insensitivity to natural concentrations.

中文翻译：

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低剂量乙醇对黑腹果蝇雄性交配成功的影响：对乙醇抗性进化的影响？

乙醇自然存在于腐烂的果实中，许多果蝇（双翅目：果蝇科）物种在其中繁殖，可能会产生对其毒性和镇静作用的抗性选择。测量暴露于一系列乙醇浓度的果蝇死亡率的研究表明，在黑腹果蝇中，来自温带地区的种群比祖先的热带非洲种群对乙醇的抵抗力更强。然而，温带黑腹果蝇的高乙醇抗性带来了一个难题，因为野生的繁殖和饲养场所很少含有足够的乙醇来杀死对乙醇更敏感的非洲热带基因型。我们假设温带种群遇到的乙醇浓度虽然通常是亚致死的，但仍然足够高，以其他方式降低适应性，潜在地产生间接选择可以在暴露于不自然的高乙醇浓度下存活的基因型。作为检验这一假设的第一步，我们比较了亚致死剂量的乙醇（与从发酵水果中获得的乙醇相当）对来自一个欧洲和一个非洲热带种群的雄性交配成功的影响。乙醇显着降低了非洲热带种群雄性的交配成功率，但对欧洲种群的雄性没有影响。我们还表明，当苍蝇被放置在具有实际乙醇浓度的培养基上时，通过蒸汽吸收的乙醇比通过喂食吸收的乙醇多得多，这表明求爱的雄性可能无法避免接触乙醇。我们假设温带人口对被高压杀死的更高抵抗力，