Data from: One step ahead: a parasitoid disperses farther and forms a wider geographic population than its fig wasp host

The structure of populations across landscapes influences the dynamics of their interactions with other species. Understanding the geographic structure of populations can thus shed light on the potential for interacting species to coevolve. Host – parasitoid interactions are widespread in nature, and also represent a significant force in the evolution of plant – insect interactions. However, there have been few comparisons of population structure between an insect host and its parasitoid. We used microsatellite markers to analyse the population genetic structure of Pleistodontes imperialis sp. 1, a fig-pollinating wasp of Port Jackson fig (Ficus rubiginosa), and its main parasitoid, Sycoscapter sp. A, in eastern Australia. Besides exploring this host – parasitoid system, our study also constitutes, to our knowledge, the first study of population structure in a non-pollinating fig wasp species. We collected matched samples of pollinators and parasitoids at several sites in two regions separated by up to 2000 km. We found that pollinators occupying the two regions represent distinct populations, but, in contrast, parasitoids formed a single population across the wide geographic range sampled. We observed genetic isolation by distance for each species, but found consistently lower FST and RST values between sites for parasitoids compared with pollinators. Previous studies have indicated that pollinators of monoecious figs can disperse over very long distances, and we provide the first genetic evidence that their parasitoids may disperse as far, if not farther. The contrasting geographic population structures of host and parasitoid highlight the potential for geographic mosaics in this important symbiotic system.

跨景观尺度的种群结构，会影响其与其他物种的互作动态。因此，解析种群的地理结构，能够揭示互作物种协同演化的潜在可能性。寄主-寄生蜂（host-parasitoid）互作在自然界中广泛存在，同时也是驱动植物-昆虫互作演化的重要力量。然而，目前针对昆虫寄主与其寄生蜂的种群结构开展的对比研究仍较为匮乏。本研究利用微卫星标记（microsatellite markers），分析了澳大利亚东部地区杰克逊港榕（Ficus rubiginosa）的无花果传粉黄蜂（fig-pollinating wasp）Pleistodontes imperialis sp. 1，及其主要寄生蜂Sycoscapter sp. A的种群遗传结构。除了解析这一寄主-寄生蜂互作系统外，据我们所知，本研究还是首次针对非传粉榕小蜂（non-pollinating fig wasp）物种开展的种群结构研究。我们在相隔最远达2000公里的两个区域的多个采样点位，收集了配对的传粉者与寄生蜂样本。研究结果显示，两个区域的传粉黄蜂各自构成独立种群；与之形成鲜明对比的是，寄生蜂在本次采样的广阔地理范围内仅形成单一种群。我们在两个物种中均观测到了距离隔离的遗传模式，但相较于传粉黄蜂，寄生蜂各采样点位间的FST与RST值始终更低。已有研究表明，雌雄同株榕的传粉黄蜂可进行长距离扩散；而本研究首次通过遗传证据证实，其寄生蜂即便没有扩散得更远，至少也能达到同等的扩散距离。寄主与寄生蜂截然不同的地理种群结构，凸显了这一重要共生系统中存在地理镶嵌演化的潜在可能。