Data from: Strong dispersal in a parasitoid wasp overwhelms habitat fragmentation and host population dynamics

The population dynamics of a parasite depend on species traits, host dynamics, and the environment. Those dynamics are reflected in the genetic structure of the population. Habitat fragmentation has a greater impact on parasites than on their hosts because resource distribution is increasingly fragmented for species at higher trophic levels. This could lead to either more or less genetic structure than the host, depending on the relative dispersal rates of species. We examined the spatial genetic structure of the parasitoid wasp Hyposoter horticola, and how it was influenced by dispersal, host population dynamics, and habitat fragmentation. The host, the Glanville fritillary butterfly, lives as a metapopulation in a fragmented landscape in the Åland islands, Finland. We collected wasps throughout the 50 by 70 km archipelago and determined the genetic diversity, spatial population structure, and genetic differentiation using 14 neutral DNA microsatellite loci. We compared genetic structure of the wasp with that of the host butterfly using published genetic data collected over the shared landscape. Using maternity assignment, we also identified full-siblings among the sampled parasitoids to estimate the dispersal range of individual females. We found that, because the parasitoid is dispersive, it has low genetic structure, is not very sensitive to habitat fragmentation, and has less spatial genetic structure than its butterfly host. The wasp is sensitive to regional rather than local host dynamics, and there is a geographic mosaic landscape for antagonistic coevolution of host resistance and parasite virulence.

寄生虫的种群动态取决于物种自身性状、宿主种群动态与环境因素，此类种群动态特征亦可体现在种群的遗传结构之中。生境破碎化对寄生虫的影响程度显著高于宿主，这是因为营养级更高的物种种群的资源分布往往更为破碎。基于不同物种间相对扩散速率的差异，寄生虫种群的遗传结构可能较宿主更为复杂，也可能更为简化。本研究聚焦于寄生蜂Hyposoter horticola的空间遗传结构，以及该结构如何受扩散能力、宿主种群动态与生境破碎化的影响。其宿主为格兰维尔贝母蝶（Glanville fritillary butterfly），该物种以集合种群（metapopulation）的形式栖息于芬兰奥兰群岛的破碎化景观中。研究团队在这片50×70公里的群岛区域内采集了寄生蜂样本，并通过14个中性DNA微卫星位点（microsatellite loci）分析了其遗传多样性、空间种群结构与遗传分化水平。本研究借助已发表的、基于同一研究区域获取的宿主蝴蝶遗传数据，对比了寄生蜂与宿主的种群遗传结构差异。通过母系分配分析，研究团队还在采样得到的寄生蜂个体中鉴定出全同胞家系，以此估算雌性个体的扩散范围。研究结果显示：由于该寄生蜂具备较强的扩散能力，其种群遗传结构水平较低，对生境破碎化的敏感性较弱，且空间遗传结构相较于宿主蝴蝶更为简单。该寄生蜂对区域尺度而非局域尺度的宿主种群动态更为敏感，同时宿主抗性与寄生毒力的拮抗协同进化存在地理镶嵌景观格局。