Institute of Zoology, Chinese Academy of Sciences, Beijing, People's Republic of China.
BMC Evol Biol. 2011 Apr 1;11:86. doi: 10.1186/1471-2148-11-86.
Figs and fig-pollinating wasp species usually display a highly specific one-to-one association. However, more and more studies have revealed that the "one-to-one" rule has been broken. Co-pollinators have been reported, but we do not yet know how they evolve. They may evolve from insect speciation induced or facilitated by Wolbachia which can manipulate host reproduction and induce reproductive isolation. In addition, Wolbachia can affect host mitochondrial DNA evolution, because of the linkage between Wolbachia and associated mitochondrial haplotypes, and thus confound host phylogeny based on mtDNA. Previous research has shown that fig wasps have the highest incidence of Wolbachia infection in all insect taxa, and Wolbachia may have great influence on fig wasp biology. Therefore, we look forward to understanding the influence of Wolbachia on mitochondrial DNA evolution and speciation in fig wasps.
We surveyed 76 pollinator wasp specimens from nine Ficus microcarpa trees each growing at a different location in Hainan and Fujian Provinces, China. We found that all wasps were morphologically identified as Eupristina verticillata, but diverged into three clades with 4.22-5.28% mtDNA divergence and 2.29-20.72% nuclear gene divergence. We also found very strong concordance between E. verticillata clades and Wolbachia infection status, and the predicted effects of Wolbachia on both mtDNA diversity and evolution by decreasing mitochondrial haplotypes.
Our study reveals that the pollinating wasp E. verticillata on F. microcarpa has diverged into three cryptic species, and Wolbachia may have a role in this divergence. The results also indicate that Wolbachia strains infecting E. verticillata have likely resulted in selective sweeps on host mitochondrial DNA.
榕果和榕小蜂通常表现出高度专一的一对一关联。然而，越来越多的研究表明，“一对一”的规则已经被打破。已经报道了共同传粉者，但我们还不知道它们是如何进化的。它们可能是由沃尔巴克氏体诱导或促进的昆虫物种形成进化而来的，沃尔巴克氏体可以操纵宿主繁殖并诱导生殖隔离。此外，沃尔巴克氏体可以影响宿主线粒体 DNA 的进化，因为沃尔巴克氏体与相关线粒体单倍型之间存在连锁关系，从而混淆了基于 mtDNA 的宿主系统发育。先前的研究表明，榕小蜂是所有昆虫类群中感染沃尔巴克氏体发生率最高的，沃尔巴克氏体可能对榕小蜂生物学有很大的影响。因此，我们期待了解沃尔巴克氏体对榕小蜂线粒体 DNA 进化和物种形成的影响。
我们调查了来自中国海南和福建 9 棵不同位置生长的榕树的 76 只传粉榕小蜂标本。我们发现，所有的榕小蜂都是形态上鉴定为垂榕小蜂，但是分为三个支系，线粒体 DNA 差异为 4.22-5.28%，核基因差异为 2.29-20.72%。我们还发现，垂榕小蜂支系与沃尔巴克氏体感染状态之间非常一致，沃尔巴克氏体对线粒体多样性和进化的预测作用是通过减少线粒体单倍型来实现的。
我们的研究表明，榕树上的传粉榕小蜂 E. verticillata 已经分化为三个隐种，而沃尔巴克氏体可能在这种分化中起作用。研究结果还表明，感染 E. verticillata 的沃尔巴克氏体菌株可能导致了宿主线粒体 DNA 的选择压力。
