Data from: Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape

A fragmented habitat becomes increasingly fragmented for species at higher trophic levels, such as parasitoids. To persist, these species are expected to possess life-history traits, such as high dispersal, that facilitate their ability to use resources that become scarce in fragmented landscapes. If a specialized parasitoid disperses widely to take advantage of a sparse host, then the parasitoid population should have lower genetic structure than the host. We investigated the temporal and spatial genetic structure of a hyperparasitoid (fourth trophic level) in a fragmented landscape over 50 × 70 km, using microsatellite markers, and compared it with the known structures of its host parasitoid, and the butterfly host which lives as a classic metapopulation. We found that population genetic structure decreases with increasing trophic level. The hyperparasitoid has fewer genetic clusters (K = 4), than its host parasitoid (K = 15), which in turn is less structured than the host butterfly (K = 27). The genetic structure of the hyperparasitoid also shows temporal variation, with genetic differentiation increasing due to reduction of the population size, which reduces the effective population size. Overall, our study confirms the idea that specialized species must be dispersive to use a fragmented host resource, but that this adaptation has limits.在破碎化生境中，处于较高营养级（trophic level）的物种（如寄生蜂（parasitoid））所面临的生境破碎化问题会愈发严重。为维持种群存续，这类物种需具备高扩散能力等生活史特征，以提升其在破碎化景观中利用稀缺资源的能力。若特化寄生蜂通过大范围扩散以利用分布稀疏的寄主，则其种群的遗传结构应较寄主更为简单。本研究以覆盖50×70 km范围的破碎化生境为研究区域，利用微卫星标记（microsatellite markers）分析了四级营养级重寄生蜂（hyperparasitoid）的时空遗传结构，并将其与已知的寄主寄生蜂、以及以典型集合种群（metapopulation）模式生存的蝶类寄主的遗传结构进行了对比。研究结果显示，种群遗传结构随营养级升高而逐渐简化。该重寄生蜂的遗传聚类群数量（K=4）少于其寄主寄生蜂（K=15），而寄主寄生蜂的遗传结构复杂度又低于蝶类寄主（K=27）。该重寄生蜂的遗传结构同时存在时间动态变化：种群规模缩减会导致有效种群大小（effective population size）降低，进而使其遗传分化程度升高。综上，本研究证实了特化物种需具备高扩散能力以利用破碎化寄主资源这一假说，但同时也表明这类适应性进化存在其极限。