Fry Adam J, Rand David M
Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island 02912, USA.
Evolution. 2002 Oct;56(10):1976-81. doi: 10.1111/j.0014-3820.2002.tb00123.x.
We have recently described a mutualistic symbiosis in which Wolbachia bacteria were shown to improve the fitness of some Drosophila melanogaster stocks. Wolbachia did not extend longevity in all Drosophila genotypes, even though 16s rDNA sequences indicated that our Drosophila stocks were infected with the same Wolbachia strain. Here, we use reciprocal hybrid crosses between two Drosophila strains, one that lived longer with Wolbachia (Z53) and one that did not (Z2), to investigate the inheritance of the survival phenotype and its dependence on the host genotype, sex, and mating conditions. Wolbachia's positive effects were more apparent in hybrid flies than in parental flies, ruling out exclusive maternal inheritance or the dependence of the survival phenotype on Wolbachia strain differences. The Wolbachia survival effects were more apparent in single-sex cages, where courtship and mating were not permitted. In these cages, nearly all flies with Wolbachia lived longer than uninfected flies, even though strain Z2 showed no Wolbachia effect in mixed-sex mating cages. We used comparisons between single- and mixed-sex cages to estimate the cost of reproduction for both sexes. Our data suggest that Wolbachia infection may increase the inferred cost of reproduction, particularly in males. Wolbachia can even produce a positive survival effect almost as large as the negative survival effect associated with reproduction. We discuss the implications of our experiments for the study of insect symbioses.
我们最近描述了一种互利共生关系，其中沃尔巴克氏体细菌被证明可提高某些黑腹果蝇品系的适应性。尽管16s rDNA序列表明我们的果蝇品系感染了相同的沃尔巴克氏体菌株，但沃尔巴克氏体并未延长所有果蝇基因型的寿命。在这里，我们使用两个果蝇品系之间的正反交杂交，一个品系（Z53）感染沃尔巴克氏体后寿命更长，另一个品系（Z2）则不然，以研究存活表型的遗传及其对宿主基因型、性别和交配条件的依赖性。沃尔巴克氏体的积极作用在杂交果蝇中比在亲本果蝇中更明显，排除了仅母系遗传或存活表型对沃尔巴克氏体菌株差异的依赖性。在不允许求偶和交配的单性别笼子中，沃尔巴克氏体对存活的影响更明显。在这些笼子里，几乎所有感染沃尔巴克氏体的果蝇都比未感染的果蝇寿命长，尽管在混合性别交配笼子中Z2品系未显示出沃尔巴克氏体的影响。我们通过比较单性别笼子和混合性别笼子来估计两性的繁殖成本。我们的数据表明，感染沃尔巴克氏体可能会增加推断的繁殖成本，尤其是在雄性中。沃尔巴克氏体甚至可以产生几乎与繁殖相关的负面存活影响一样大的积极存活影响。我们讨论了我们的实验对昆虫共生研究的意义。
