BACKGROUND Understanding the forces that maintain diversity across a range of scales is at the very heart of biology. Frequency-dependent processes are generally recognized as the most central process for the maintenance of ecological diversity. The same is, however, not generally true for genetic diversity. Negative frequency dependent selection, where rare genotypes have an advantage, is often regarded as a relatively weak force in maintaining genetic variation in life history traits because recombination disassociates alleles across many genes. Yet, many regions of the genome show low rates of recombination and genetic variation in such regions (i.e., supergenes) may in theory be upheld by frequency dependent selection. RESULTS We studied what is essentially a ubiquitous life history supergene (i.e., mitochondrial DNA) in the fruit fly Drosophila subobscura, showing sympatric polymorphism with two main mtDNA genotypes co-occurring in populations world-wide. Using an experimental evolution approach involving manipulations of genotype starting frequencies, we show that negative frequency dependent selection indeed acts to maintain genetic variation in this region. Moreover, the strength of selection was affected by food resource conditions. CONCLUSIONS Our work provides novel experimental support for the view that balancing selection through negative frequency dependency acts to maintain genetic variation in life history genes. We suggest that the emergence of negative frequency dependent selection on mtDNA is symptomatic of the fundamental link between ecological processes related to resource use and the maintenance of genetic variation.

中文翻译：

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负频率依赖性选择有助于维持线粒体DNA的整体多态性。

背景技术了解在各种尺度上维持多样性的力是生物学的核心。频率相关的过程通常被认为是维护生态多样性的最核心过程。但是，对于遗传多样性通常情况并非如此。负频率依赖性选择在稀有基因型具有优势的情况下通常被认为是维持生命史特征遗传变异的相对较弱的力量，因为重组使许多基因之间的等位基因解离。然而，基因组的许多区域显示出低重组率，并且在这些区域（即，超基因）中的遗传变异在理论上可以通过频率依赖性选择来维持。结果我们研究了本质上无所不在的生命史超基因（即 果蝇果蝇的线粒体DNA）显示出同态多态性，在全世界的人群中同时存在两种主要的mtDNA基因型。使用涉及基因型起始频率操纵的实验进化方法，我们表明负频率依赖性选择确实起到维持该区域遗传变异的作用。此外，选择的强度受到粮食资源条件的影响。结论我们的工作为以下观点提供了新颖的实验支持：通过负频率依赖性平衡选择可维持生命历史基因的遗传变异。我们建议对mtDNA负频率依赖性选择的出现是与资源利用相关的生态过程与遗传变异的维持之间基本联系的征兆。