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、宿主动态与环境因素。此类种群动态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甚于宿主，这是因为营养级更高的物种其资源分布愈发破碎。这可能使得寄生虫的遗传结构较宿主更为复杂或简单，具体取决于不同物种间的相对扩散速率。 本研究针对寄生蜂霍氏狭姬蜂（Hyposoter horticola）的空间遗传结构展开分析，探究扩散、宿主种群动态及生境破碎化对其空间遗传结构的影响。其宿主为格兰维尔格纹蛱蝶（Glanville fritillary butterfly），该物种在芬兰奥兰群岛的破碎化景观中以集合种群（metapopulation）的形式存续。 本研究在这片50×70公里的群岛范围内采集了寄生蜂样本，并通过14个中性DNA微卫星（microsatellite）位点，测定了样本的遗传多样性、空间种群结构及遗传分化。本研究利用已发表的、基于该共同研究区域获取的宿主蝴蝶遗传数据，对寄生蜂与宿主的遗传结构进行对比分析。 通过母系归属（maternity assignment）分析，本研究还在采样的寄生蜂个体中鉴定出全同胞个体（full-siblings），以此估算雌性寄生蜂的扩散范围。 研究结果表明：由于该寄生蜂具备较强的扩散能力，其遗传分化程度较低，对生境破碎化的敏感性较弱，且空间遗传结构较宿主蝴蝶更为简单。该寄生蜂对区域尺度而非局域尺度的宿主动态更为敏感，同时存在宿主抗性与寄生毒力拮抗协同进化的地理镶嵌景观（geographic mosaic landscape）。