Koukou Katerina, Pavlikaki Haris, Kilias George, Werren John H, Bourtzis Kostas, Alahiotis Stamatis N
Department of Biology, Division of Genetics, University of Patras, Greece.
Evolution. 2006 Jan;60(1):87-96.
Speciation depends on the establishment of reproductive isolation between populations of the same species. Whether assortative mating evolves as a by-product of adaptation is a major question relevant to the origin of species by reproductive isolation. The long-term selection populations used here were originally established 30 years ago from a single cage population (originating from a maternal one) and subsequently subjected to divergent selection for tolerance of toxins in food (heavy metals versus ethanol) to investigate this question. Those populations now differ in sexual isolation and Wolbachia infection status. Wolbachia are common and widespread bacteria infecting arthropods and nematodes. Attention has recently focused on their potential role in insect speciation, due to post-mating sperm-egg incompatibilities induced by the bacteria. In this paper we examine the potential effect of Wolbachia on the level of sexual isolation. By antibiotic curing, we show that removal of Wolbachia decreases levels of mate discrimination (sexual isolation index) between populations by about 50%. Backcrossing experiments confirm that this effect is due to infection status rather than to genetic changes in the populations resulting from antibiotic treatment. Antibiotic treatment has no effect on mate discrimination level between uninfected populations. Our findings suggest that the presence of Wolbachia (or another undetected bacterial associate) act as an additive factor contributing to the level of pre-mating isolation between these Drosophila melanogaster populations. Given the ubiquity of bacterial associates of insects, such effects could be relevant to some speciation events.
物种形成取决于同一物种不同种群之间生殖隔离的建立。选择性交配是否作为适应的副产品而进化，是一个与通过生殖隔离形成物种的起源相关的主要问题。这里使用的长期选择种群最初是30年前从单个笼养种群（源自一个母本种群）建立的，随后针对食物中毒素（重金属与乙醇）的耐受性进行了定向选择，以研究这个问题。这些种群现在在性隔离和沃尔巴克氏体感染状态方面存在差异。沃尔巴克氏体是感染节肢动物和线虫的常见且广泛存在的细菌。由于这种细菌诱导的交配后精卵不相容性，最近人们的注意力集中在它们在昆虫物种形成中的潜在作用上。在本文中，我们研究了沃尔巴克氏体对性隔离水平的潜在影响。通过抗生素清除，我们表明去除沃尔巴克氏体会使种群之间的配偶识别水平（性隔离指数）降低约50%。回交实验证实，这种影响是由于感染状态，而不是由于抗生素处理导致的种群基因变化。抗生素处理对未感染种群之间的配偶识别水平没有影响。我们的研究结果表明，沃尔巴克氏体（或另一种未检测到的细菌共生体）的存在是导致这些黑腹果蝇种群之间交配前隔离水平的一个附加因素。鉴于昆虫细菌共生体的普遍存在，这种影响可能与某些物种形成事件有关。
