Thiamethoxam soil contaminations reduce the fertility of a soil-dwelling beetle (Aethina tumida)

The sixth mass extinction event is underway and environmental pollution is one major driver. Of particular concern are global insect declines, as their roles in ecosystem functionality and human food security are indispensable. Even though environmental pollutants are known to reduce fertility, their potential effects on insect fitness remain poorly understood - especially for soil-dwelling species. Here, we show that fertility of soil-dwelling beetles, Aethina tumida, is reduced, on average, by half due to field-realistic neonicotinoid soil contaminations. In the laboratory, pupating beetles were exposed via soil to concentrations of the neonicotinoid thiamethoxam that reflect global pollution of agricultural and natural habitats. Emerged adult phenotypes and reproduction were measured, and even the lowest concentration reported from natural habitats reduced subsequent reproduction by 50%. The data are most likely a conservative estimate as the beetles were only exposed during pupation. Since the tested concentrations reflect ubiquitous global soil pollution, the data reveal a plausible mechanism for ongoing insect declines. An immediate reduction in environmental pollutants is urgently required if our aim is to mitigate the prevailing loss of species biodiversity.第六次生物大灭绝事件正在上演，环境污染是其主要驱动因素之一。尤其值得关注的是全球范围内的昆虫种群衰退，因为昆虫在生态系统功能维持与人类粮食安全中扮演着不可或缺的角色。尽管已知环境污染物会降低昆虫繁殖力，但人们对其对昆虫适合度的潜在影响仍知之甚少，针对土壤栖息物种的相关研究尤为匮乏。本研究表明，受符合野外实际浓度的新烟碱类（neonicotinoid）土壤污染物影响，土壤栖息的蜂箱小甲虫（Aethina tumida）的平均繁殖力下降了50%。实验中，研究人员通过土壤将化蛹期的蜂箱小甲虫暴露于新烟碱类杀虫剂噻虫嗪（thiamethoxam）的不同浓度环境中，这些浓度均匹配农业与自然栖息地的全球污染实际水平。研究人员对羽化后的成虫表型与繁殖能力进行了检测，结果显示，即使是自然栖息地中检测到的最低浓度污染物，也会使后续繁殖能力下降50%。由于蜂箱小甲虫仅在化蛹期接受污染物暴露，本研究数据大概率属于保守估算值。鉴于实验所用污染物浓度匹配全球普遍存在的土壤污染水平，本研究数据揭示了当前昆虫种群衰退的一项合理作用机制。若要减缓当前的生物多样性丧失趋势，亟需立即降低环境污染物排放。