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性状、宿主动态与环境条件。此类动态可反映于种群的遗传结构（genetic structure）之中。生境破碎化（habitat fragmentation）对寄生虫的影响程度高于宿主，原因在于营养级（trophic levels）越高的物种，其资源分布愈发趋于破碎。依据物种间相对扩散速率的差异，生境破碎化可能导致寄生虫的遗传结构较宿主更高或更低。
本研究针对寄生蜂（parasitoid wasp）霍氏潜蝇茧蜂（Hyposoter horticola）的空间遗传结构展开探究，分析其受扩散作用、宿主种群动态及生境破碎化的影响模式。该寄生蜂的宿主为格朗维尔贝母蝶（Glanville fritillary butterfly），此蝶在芬兰奥兰群岛（Åland islands）的破碎化景观中以集合种群（metapopulation）的形式存续。
研究团队在50×70 km的群岛区域内采集寄生蜂样本，借助14个中性DNA微卫星位点（neutral DNA microsatellite loci）测定其遗传多样性、空间种群结构及遗传分化（genetic differentiation）。本研究利用已发表的共享景观范围内的宿主蝴蝶遗传数据，对比了寄生蜂与宿主的遗传结构差异。通过母本鉴定（maternity assignment），研究还对采样寄生蜂中的全同胞（full-siblings）个体进行了识别，以此估算雌性个体的扩散范围。
研究结果表明，由于该寄生蜂具备较强的扩散能力，其遗传结构水平较低，对生境破碎化的敏感性较弱，且空间遗传结构程度低于其宿主蝴蝶。该寄生蜂对区域尺度而非局域尺度的宿主动态更为敏感，同时存在宿主抗性与寄生虫毒力之间的拮抗协同进化（antagonistic coevolution）地理镶嵌景观。