How can sex ratio distorters reach extreme prevalences?: Male-killing Wolbachia are not suppressed and have near-perfect vertical transmission efficiency in Acraea encedon
How can sex ratio distorters reach extreme prevalences?: Male-killing Wolbachia are not suppressed and have near-perfect vertical transmission efficiency in Acraea encedon
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DOI：
10.1111/j.0014-3820.2002.tb00152.x
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发表时间：
2002-11-01
期刊：
影响因子：
3.3
通讯作者：
Majerus, MEN
中科院分区：
文献类型：
--
作者：
Jiggins, FM;Randerson, JP;Majerus, MEN
在许多昆虫中发现，母体传播的细菌会在雄性宿主发育早期杀死它们。这些寄生虫通常感染1-30%的野生雌性，但在少数几种昆虫中，患病率超过95%。我们在蝴蝶Acraea encedon中调查了一个这样的病例，它感染了一种杀死雄性的沃尔巴克氏菌。我们测量了影响寄生虫流行的三个关键参数：传播效率、受感染雄性的存活率和感染的直接成本。我们观察到，所有野生雌性都将细菌传播给它们的所有后代，所有受感染的雄性在野生种群中死亡。我们无法在实验室培养中检测到感染的任何生理代价。这些观察结果解释了雄斑拟虫的高流行率，因为理论预测，在这些条件下，寄生虫将传播到固定。如果雄性的死亡对幸存的受感染的雌性有益，这种情况就会发生。因此，问题就变成了为什么这种细菌没有达到固定状态，并由于雄性蝴蝶的缺乏而导致蝴蝶灭绝。因此，我们研究了雄性是否选择与未感染的雌性交配，而不是与感染的雌性交配，因为这将阻止细菌达到固定。我们在大多数偏向雌性的种群中发现的处女“渗漏群”中测试了这一假设，并没有发现任何配偶选择的证据。综上所述，该男性杀手具有传播效率高、成本低的特点，具有较高的流行率，但维持人群中未感染女性的因素尚不清楚。
Maternally transmitted bacteria that kill male hosts early in their development are found in many insects. These parasites typically infect 1-30% of wild females, but in a few species of insects, prevalences exceed 95%. We investigated one such case in the butterfly Acraea encedon, which is infected with a male-killing Wolbachia bacterium. We measured three key parameters that affect the prevalence of the parasite: transmission efficiency, rate of survival of infected males, and the direct cost of infection. We observed that all wild females transmit the bacterium to all their offspring and that all infected males die in wild populations. We were unable to detect any physiological cost to infection in lab culture. These observations explain the high prevalence of the A. encedon male killer, as theory predicts that under these conditions the parasite will spread to fixation. This will occur provided the death of males provides some benefit to the surviving infected females. The problem therefore becomes why the bacterium has not reached fixation and driven the butterfly extinct due to the shortage of males. We therefore investigated whether males choose to mate with uninfected rather than infected females, as this would prevent the bacterium from reaching fixation. We tested this hypothesis in the "lekking swarms" of virgin females found in the most female-biased populations, and were unable to detect any evidence of mate choice. In conclusion, this male killer has spread to high prevalence because it has a high transmission efficiency and low cost, but the factors maintaining uninfected females in the population remain unknown.