van Alphen Jacques J M, Fernhout Bart Jan
1Naturalis Biodiversity Centre, 2333 CR Leiden, The Netherlands.
Arista Bee Research Foundation, Nachtegaal 2, 5831 WL Boxmeer, The Netherlands.
Zoological Lett. 2020 May 18;6:6. doi: 10.1186/s40851-020-00158-4. eCollection 2020.
We examine evidence for natural selection resulting in becoming tolerant or resistant to mites in different bee populations. We discuss traits implicated in 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 . Finally, bees may be tolerant of high 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 comes from South Africa and from Africanized honeybees in South America. Initially, 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 invasion. Natural selection in Europe and North America has not resulted in large-scale resistance. Upon arrival of , 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.
我们研究了自然选择导致不同蜜蜂种群对螨虫产生耐受性或抗性的证据。我们讨论了与抗性相关的性状以及如何对它们进行测量。我们表明，所使用的一些测量方法具有模糊性，因为它们测量的是多种性状的组合。除了行为性状，如移除受感染的蛹、梳理以去除蜜蜂身上的螨虫或幼虫气味外，小蜂群规模、频繁分蜂以及较小的巢房尺寸也可能有助于降低螨虫的繁殖率。最后，当蜜蜂对与蜂群崩溃相关的病毒具有抗性或耐受性时，它们可能对高螨虫感染具有耐受性。我们提供证据表明蜜蜂是一种极度杂交的物种。交配结构对于自然选择的运作方式很重要。针对螨虫成功进行自然选择抗性性状的证据来自南非和南美洲的非洲化蜜蜂。最初，螨虫密度很高，约30%的蜂群死亡，但在其传播后不久，每个蜂巢中的螨虫数量减少，蜂群未经处理也存活了下来。这表明当很大一部分种群在最初的螨虫入侵中存活下来时，自然选择可以在大型随机交配种群中导致抗性。欧洲和北美的自然选择尚未导致大规模抗性。螨虫到达后，欧洲蜜蜂中对抗螨虫及相关病毒的性状频率很低。这迫使养蜂人通过化学处理来保护蜜蜂，从而阻碍了自然选择。在瑞典一项关于隔离交配种群自然选择的实验中，只有7%的蜂群存活下来，导致严重的近亲繁殖。其他对未经处理的存活蜂群的实验失败了，因为杂交抵消了选择的效果。如果防止遗传变异的丧失，封闭交配种群中的蜂群水平选择可以更容易地进行，因为自然选择不会被抗性基因的扩散所抵消。在大型随机交配种群中，可以使用选择性育种将抗性水平提高到一个阈值水平，在这个水平上有望由自然选择接管。
