There is increasing evidence about negative effects of fungicides on non-target organisms, including parasitic species, which are key elements in food webs. Previous experiments showed that environmentally relevant concentrations of fungicide tebuconazole are toxic to the microparasite Metschnikowia bicuspidata, a yeast species that infects the planktonic crustacean Daphnia spp. However, due to their short-term nature, this and other experimental studies were not able to test if parasites could potentially adapt to these contaminants. Here, we tested if M. bicuspidata parasite can adapt to tebuconazole selective pressure. Infected D. magna lineages were reared under control conditions (no tebuconazole) and environmentally realistic tebuconazole concentrations, for four generations, and their performance was compared in a follow-up reciprocal assay. Additionally, we assessed whether the observed effects were transient (phenotypic) or permanent (genetic), by reassessing parasite fitness after the removal of selective pressure. Parasite fitness was negatively affected throughout the multigenerational exposure to the fungicide: prevalence of infection and spore load decreased, whereas host longevity increased, in comparison to control (naive) parasite lineages. In a follow-up reciprocal assay, tebuconazole-conditioned (TEB) lineages performed worse than naive parasite lineages, both in treatments without and with tebuconazole, confirming the cumulative negative effect of tebuconazole. The underperformance of TEB lineages was rapidly reversed after removing the influence of the selective pressure (tebuconazole), demonstrating that the costs of prolonged exposure to tebuconazole were phenotypic and transient. The microparasitic yeast M. bicuspidata did not reveal potential for rapid evolution to an anthropogenic selective pressure; instead, the long-term exposure to tebuconazole was hazardous to this non-target species. These findings highlight the potential environmental risks of azole fungicides on non-target parasitic fungi. The underperformance of these microbes and their inability to adapt to such stressors can interfere with the key processes where they intervene. Further research is needed to rank fungicides based on the hazard to non-target fungi (parasites, but also symbionts and decomposers), towards more effective management and protective legislation.

越来越多的证据表明，杀菌剂对非目标生物（包括寄生物）具有负面影响，而非目标生物是食物网中的关键元素。先前的实验表明，与环境有关的浓度的杀菌剂戊丁康对微寄生虫Metschnikowia bicuspidata有毒，该酵母菌感染浮游甲壳类水蚤。但是，由于它们的短期性质，该研究和其他实验研究无法测试寄生虫是否可能潜在地适应这些污染物。在这里，我们测试了M. bicuspidata寄生虫是否可以适应戊唑醇的选择性压力。感染了D. magna在控制条件下（无戊唑醇）和符合环境要求的戊唑醇浓度饲养了四代人，在后续的交互试验中比较了它们的性能。此外，我们通过去除选择性压力后重新评估寄生虫适应性，评估了观察到的效果是短暂的（表型）还是永久的（遗传的）。在多代接触杀真菌剂的过程中，寄生虫适应性受到负面影响：与对照（天真）寄生虫谱系相比，感染率和孢子量降低，而宿主寿命延长。在后续的双向分析中，在未使用或未使用戊唑醇的治疗中，戊唑醇条件下（TEB）的谱系均比未处理过的寄生虫谱系差，证实了戊唑醇的累积负效应。消除选择性压力（戊酸康唑）的影响后，TEB谱系的不良表现迅速得到逆转，表明长时间暴露于戊康唑的费用是表型的和短暂的。微寄生酵母M. bicuspidata没有揭示迅速进化为人为选择压力的潜力。相反，长期接触戊唑醇对这种非目标物种有害。这些发现突出了吡咯类杀菌剂对非目标寄生真菌的潜在环境风险。这些微生物的表现不佳以及无法适应此类压力源会干扰它们干预的关键过程。需要进一步的研究，根据对非目标真菌（寄生虫，还有共生体和分解物）的危害对杀真菌剂进行分级，以实现更有效的管理和保护性立法。