The biology of parasitoids in natural ecosystems remain very poorly studied, while they are key species for their functioning. Here we focused on Phobocampe confusa, a vanessines specialist, responsible for high mortality rates in very emblematic butterfly species in Europe (genus Aglais). We studied its ecology and genetic structure in connection with those of its host butterflies in Sweden. To this aim, we gathered data from 428 P. confusa individuals reared from 6094 butterfly larvae (of A. urticae, A. io and in two occasions of Araschnia levana) collected over two years (2017 and 2018) and 19 sites distributed along a 500 km latitudinal gradient. We found that P. confusa is widely distributed along the latitudinal gradient. Its distribution is constrained over time by the phenology of its hosts. The large variation in climatic conditions between sampling years explains the decrease in phenological overlap between P. confusa and its hosts in 2018 and the 33.5% decrease in the number of butterfly larvae infected. At least in this study, P. confusa seems to favour A. urticae as host: while it parasitized nests of A. urticae and A. io equally, the proportion of larvae is significantly higher for A. urticae. At the landscape scale, P. confusa is almost exclusively found in vegetated open land and near deciduous forests, whereas artificial habitats are negatively correlated with the likelihood of a nest to be parasitized. The genetic analyses on 89 adult P. confusa and 87 adult A. urticae using COI and AFLP markers reveal a low genetic diversity in P. confusa and a lack of population genetic structure in both species, at the scale of our sampling. Further genetic studies using high-resolution genomics tools will be required to better understand the population genetic structure of P. confusa, its biotic interactions with its hosts, and ultimately the stability and the functioning of natural ecosystems.

中文翻译：

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寄生蜂Phobocampe confusa（膜翅目：Ichneumonidae）与其寄主Aglais物种（鳞翅目：Numphalidae）的生态和种群遗传学。

在自然生态系统中，寄生生物的生物学研究还很薄弱，尽管它们是其功能的关键物种。在这里，我们重点研究了Vanessines专家Phobocampe confusa，他负责欧洲极具象征意义的蝴蝶物种（Aglais属）的高死亡率。我们研究了其生态学和遗传结构及其在瑞典的寄主蝴蝶。为此，我们收集了从两年（2017年和2018年）收集的6094个蝴蝶幼虫（A. urticae，A。io和两次Araschnia levana）饲养的428个P. confusa个体的数据，并沿500公里纬度梯度。我们发现P. confusa沿纬度梯度广泛分布。随着时间的流逝，宿主的物候特性限制了它的分布。采样年之间气候条件的巨大变化说明，P。confusa及其寄主之间的物候重叠减少，2018年被感染的蝴蝶幼虫数量减少了33.5％。至少在这项研究中，孔子假单胞菌似乎偏爱荨麻疹作为寄主：尽管它同时寄生了荨麻疹和拟南芥的巢，但是幼虫的比例明显高于荨麻疹。在景观尺度上，P。confusa几乎仅在植被开阔的土地和落叶林中发现，而人工栖息地与巢被寄生的可能性呈负相关。使用COI和AFLP标记对89个成年的野菜假单胞菌和87个成年的荨麻疹进行了遗​​传分析，结果表明，这两个物种的分离性都很低，缺乏种群遗传结构，以我们的抽样规模。将需要使用高分辨率基因组学工具进行进一步的遗传研究，以更好地了解孔雀假单胞菌的种群遗传结构，其与寄主的生物相互作用，并最终了解自然生态系统的稳定性和功能。