We examine evidence for natural selection resulting in Apis mellifera becoming tolerant or resistant to Varroa mites in different bee populations. We discuss traits implicated in Varroa resistance and how they can be measured. We show that some of the measurements used are ambiguous, as they measure a combination of traits. In addition to behavioural traits, such as removal of infested pupae, grooming to remove mites from bees or larval odours, small colony size, frequent swarming, and smaller brood cell size may also help to reduce reproductive rates of Varroa. Finally, bees may be tolerant of high Varroa infections when they are resistant or tolerant to viruses implicated in colony collapse. We provide evidence that honeybees are an extremely outbreeding species. Mating structure is important for how natural selection operates. Evidence for successful natural selection of resistance traits against Varroa comes from South Africa and from Africanized honeybees in South America. Initially, Varroa was present in high densities and killed about 30% of the colonies, but soon after its spread, numbers per hive decreased and colonies survived without treatment. This shows that natural selection can result in resistance in large panmictic populations when a large proportion of the population survives the initial Varroa invasion. Natural selection in Europe and North America has not resulted in large-scale resistance. Upon arrival of Varroa, the frequency of traits to counter mites and associated viruses in European honey bees was low. This forced beekeepers to protect bees by chemical treatment, hampering natural selection. In a Swedish experiment on natural selection in an isolated mating population, only 7% of the colonies survived, resulting in strong inbreeding. Other experiments with untreated, surviving colonies failed because outbreeding counteracted the effects of selection. If loss of genetic variation is prevented, colony level selection in closed mating populations can proceed more easily, as natural selection is not counteracted by the dispersal of resistance genes. In large panmictic populations, selective breeding can be used to increase the level of resistance to a threshold level at which natural selection can be expected to take over.

中文翻译：

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自然选择，选择性育种以及蜜蜂（Apis mellifera）对Varroa的抗性进化。

我们检查了自然选择的证据，导致蜜蜂在不同的蜜蜂种群中对蜜蜂产生耐受性或抗性。我们讨论了与Varroa抗性有关的性状以及如何对其进行测量。我们显示，由于所使用的某些度量标准是对特征的组合，因此它们是模棱两可的。除了行为特征，例如去除受感染的up，修饰以去除蜜蜂或幼虫气味的螨虫外，较小的菌落大小，频繁的成群繁殖和较小的巢细胞大小也可能有助于降低Varroa的繁殖率。最后，当蜜蜂对与菌落崩溃有关的病毒有抗性或耐受性时，它们可能对高Varroa感染具有耐受性。我们提供的证据表明，蜜蜂是极远亲繁殖的物种。配合结构对于自然选择的运作方式很重要。南非和南美的非洲蜜蜂成功地自然选择出了针对Varroa的抗性性状的证据。最初，Varroa以高密度存在并杀死了约30％的菌落，但在其扩散后不久，每个蜂巢的数量减少了，菌落未经治疗就得以存活。这表明，当大部分人口幸存于最初的Varroa入侵中时，自然选择可在大的恐慌种群中产生抗性。欧洲和北美的自然选择并未导致大规模的抵抗。当Varroa到达时，欧洲蜜蜂抵抗螨虫和相关病毒的性状发生率很低。这迫使养蜂人通过化学处理保护蜜蜂，从而妨碍了自然选择。瑞典在一个孤立的交配种群中进行自然选择的实验中，只有7％的殖民地得以幸存，导致近交能力强。其他未经处理的存活菌落的实验失败了，因为远交抵消了选择的影响。如果能防止遗传变异的丧失，封闭的交配种群中的菌落水平选择将更容易进行，因为抗性基因的扩散不会抵消自然选择。在大的恐慌种群中，可以使用选择性育种将抗性水平提高到可以预期自然选择接管的阈值水平。如果能防止遗传变异的丧失，封闭的交配种群中的菌落水平选择将更容易进行，因为抗性基因的扩散不会抵消自然选择。在大的恐慌种群中，可以使用选择性育种将抗性水平提高到可以预期自然选择接管的阈值水平。如果能防止遗传变异的丧失，封闭的交配种群中的菌落水平选择将更容易进行，因为抗性基因的扩散不会抵消自然选择。在大型的恐慌种群中，可以使用选择性育种将抗性水平提高到可以预期自然选择接管的阈值水平。