Data from: Sex allocation theory reveals a hidden cost of neonicotinoid exposure in a parasitoid wasp

Sex allocation theory has proved to be one the most successful theories in evolutionary ecology. However, its role in more applied aspects of ecology has been limited. Here we show how sex allocation theory helps uncover an otherwise hidden cost of neonicotinoid exposure in the parasitoid wasp Nasonia vitripennis. Female N. vitripennis allocate the sex of their offspring in line with Local Mate Competition (LMC) theory. Neonicotinoids are an economically important class of insecticides, but their deployment remains controversial, with evidence linking them to the decline of beneficial species. We demonstrate for the first time to our knowledge, that neonicotinoids disrupt the crucial reproductive behaviour of facultative sex allocation at sub-lethal, field-relevant doses in N. vitripennis. The quantitative predictions we can make from LMC theory show that females exposed to neonicotinoids are less able to allocate sex optimally and that this failure imposes a significant fitness cost. Our work highlights that understanding the ecological consequences of neonicotinoid deployment requires not just measures of mortality or even fecundity reduction among non-target species, but also measures that capture broader fitness costs, in this case offspring sex allocation. Our work also highlights new avenues for exploring how females obtain information when allocating sex under LMC.性别分配理论（sex allocation theory）已被证实为进化生态学领域最成功的理论之一。然而，其在更具应用导向的生态学分支中的作用却较为有限。本研究揭示了性别分配理论如何帮助我们发现寄生蜂丽金小蜂（Nasonia vitripennis）暴露于新烟碱类（neonicotinoid）时所产生的一种此前未被察觉的潜在代价。雌性丽金小蜂会依据局部配偶竞争（Local Mate Competition, LMC）理论来优化子代性别分配。新烟碱类是一类经济价值极高的杀虫剂，但其田间应用仍存在广泛争议，已有研究证据表明该类药剂与有益物种种群的衰退存在关联。据我们所知，本研究首次证实：在亚致死且符合田间实际环境的剂量下，新烟碱类会干扰丽金小蜂的兼性性别分配（facultative sex allocation）这一关键生殖行为。基于LMC理论可得出定量预测：暴露于新烟碱类的雌性个体无法最优地分配子代性别，而这种分配失误将带来显著的适合度代价。本研究强调，要全面厘清新烟碱类药剂应用的生态后果，不仅需要评估非靶标物种的死亡率乃至繁殖力下降情况，还需纳入能够反映更广泛适合度代价的相关指标——在本研究中即为子代性别分配相关的评估维度。本研究同时为探索雌性个体在LMC情境下进行性别分配时如何获取信息开辟了全新的研究方向。