Insects with aquatic larval and terrestrial adult life stages are a key component of coupled aquatic-terrestrial ecosystems. Thus, stressors applied to water bodies adversely affecting those larvae have the potential to influence the riparian zone through altered emergence, with differences in prey availability, timing, or nutrition. In this study, the common model organism Chironomus riparius, a species of Chironomidae (Diptera), was used. This selection was further motivated by its wide distribution in European freshwaters and its importance as prey for terrestrial predators. A stressor of high importance in this context is the globally used mosquito control agent Bacillus thuringiensis var. israelensis (Bti) which has been shown to affect Chironomidae. Here, we investigated the ability of chironomid populations to adapt to a regularly applied stressor, leading to a reduced impact of Bti. Therefore, the initial sensitivity of laboratory populations of C. riparius was investigated under the influence of field-relevant Bti treatments (three doses × two application days) and different food sources (high-quality TetraMin vs. low-quality Spirulina). Following a chronic exposure to Bti over six months, the sensitivity of pre-exposed and naïve populations was re-evaluated. Food quality had a strong impact on emergence timing and nutrient content. In addition, alterations in emergence time as well as protein and lipid contents of chronically exposed populations indicated a selection for individuals of advantageous energetics, potentially leading to a more efficient development while combating Bti. Signs of adaptation could be confirmed in five out of 36 tested scenarios suggesting adaptation to Bti at the population level. Adaptive responses of one or several species could theoretically (via eco-evolutionary dynamics) result in a community shift, favouring the prevalence of Bti-tolerant species. (In)direct effects of Bti and the adaptive responses at both population and community levels could affect higher trophic levels and may determine the fate of meta-ecosystems.

中文翻译：

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Chironomus riparius 对慢性 Bti 暴露的表型适应：对出苗时间和营养成分含量的影响


具有水生幼虫和陆生成虫生命阶段的昆虫是水生-陆地耦合生态系统的关键组成部分。因此，对这些幼虫产生不利影响的水体的压力源有可能通过改变出苗率来影响河岸区，猎物可用性、时间或营养存在差异。在这项研究中，使用了常见的模式生物 Chironomus riparius，一种 Chironomidae （Diptera）。它在欧洲淡水中的广泛分布及其作为陆地捕食者猎物的重要性进一步推动了这种选择。在这种情况下，一个非常重要的压力源是全球使用的蚊子控制剂苏云金芽孢杆菌 （Bti），它已被证明会影响 Chironomidae。在这里，我们研究了 chironomid 种群适应定期施加的压力源的能力，从而减少了 Bti 的影响。因此，在现场相关 Bti 处理（三剂×两个施用日）和不同食物来源（高质量 TetraMin 与低质量螺旋藻）的影响下，研究了 C. riparius 实验室种群的初始敏感性。在长期暴露于 Bti 超过 6 个月后，重新评估了预先暴露和未接触人群的敏感性。食物质量对出苗时间和营养成分有很大影响。此外，长期暴露人群的出苗时间以及蛋白质和脂质含量的变化表明选择了具有优势能量的个体，这可能会导致在对抗 Bti 的同时更有效地发育。在 36 个测试场景中，有 5 个可以确认适应迹象，这表明在种群水平上适应了 Bti。 理论上（通过生态进化动力学）一个或多个物种的适应性反应可能导致群落转变，有利于耐 Bti 物种的普遍存在。Bti 的（间接）影响以及种群和群落水平的适应性反应可能会影响更高的营养级，并可能决定元生态系统的命运。