Abstract Agricultural intensification has caused population declines and reduced species diversity in both arthropods and their predators. Despite conservation and habitat management implications, the effects of land-use change on the trophic relationships between nocturnal arthropod predators and their prey have seldom been described. To assess how arthropodivorous bats may have shifted their diets in response to land-use changes, we compared bulk δ 13C and δ 15N values from little brown and big brown bat museum specimens and carcasses collected in the Upper Midwestern region of the United States from 1898 to 2019. As an exploratory analysis, we also investigated relationships between isotopic values and climate or landcover variables to quantify potential correlations with changes in arthropodivorous bat foraging patterns over time. Overall, we found that isotopic niche overlap of little brown and big brown bats increased from 24% to 45% between historical and contemporary time periods. Our results indicate that the isotopic niches of little brown bats have been largely conserved, whereas the isotopic niches of big brown bats are more flexible and became more similar to little brown bats over time. Further analyses showed that stable isotope values from arthropodivorous bat tissues were also correlated with certain landcover variables such as the prevalence of wetland, forest, and grassland habitats, but not with the prevalence of agricultural land on a local scale. These findings suggest that the foraging patterns of some aerial arthropodivores have shifted in response to the loss of habitat diversity and corresponding changes in prey resources.

中文翻译：

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比较过去一个世纪在以农业为主的景观中的小棕蝙蝠和大棕蝙蝠同位素生态位

摘要 农业集约化导致节肢动物及其捕食者的种群数量下降和物种多样性减少。尽管对保护和栖息地管理有影响，但很少描述土地利用变化对夜间节肢动物捕食者与其猎物之间营养关系的影响。为了评估节肢食蝙蝠如何改变它们的饮食以应对土地利用的变化，我们比较了 1898 年在美国中西部地区收集的小棕蝙蝠和大棕蝙蝠博物馆标本和尸体的体积 δ 13C 和 δ 15N 值到 2019 年。作为一项探索性分析，我们还调查了同位素值与气候或土地覆盖变量之间的关系，以量化与节肢食蝙蝠觅食模式随时间变化的潜在相关性。总体而言，我们发现在历史和当代时期，小棕蝙蝠和大棕蝙蝠的同位素生态位重叠从 24% 增加到 45%。我们的研究结果表明，棕色小蝙蝠的同位素生态位在很大程度上得到了保护，而大棕色蝙蝠的同位素生态位更加灵活，并且随着时间的推移变得与小棕色蝙蝠更加相似。进一步的分析表明，节肢动物蝙蝠组织的稳定同位素值也与某些土地覆盖变量相关，例如湿地、森林和草地栖息地的普遍性，但与当地农业用地的普遍性无关。这些发现表明，一些空中节肢动物的觅食模式已经发生变化，以应对栖息地多样性的丧失和猎物资源的相应变化。我们发现，在历史和当代时期，小棕蝙蝠和大棕蝙蝠的同位素生态位重叠从 24% 增加到 45%。我们的研究结果表明，棕色小蝙蝠的同位素生态位在很大程度上得到了保护，而大棕色蝙蝠的同位素生态位更加灵活，并且随着时间的推移变得与小棕色蝙蝠更加相似。进一步的分析表明，节肢动物蝙蝠组织的稳定同位素值也与某些土地覆盖变量相关，例如湿地、森林和草地栖息地的普遍性，但与当地农业用地的普遍性无关。这些发现表明，一些空中节肢动物的觅食模式已经发生变化，以应对栖息地多样性的丧失和猎物资源的相应变化。我们发现，在历史和当代时期，小棕蝙蝠和大棕蝙蝠的同位素生态位重叠从 24% 增加到 45%。我们的研究结果表明，棕色小蝙蝠的同位素生态位在很大程度上得到了保护，而大棕色蝙蝠的同位素生态位更加灵活，并且随着时间的推移变得与小棕色蝙蝠更加相似。进一步的分析表明，节肢动物蝙蝠组织的稳定同位素值也与某些土地覆盖变量相关，例如湿地、森林和草地栖息地的普遍性，但与当地农业用地的普遍性无关。这些发现表明，一些空中节肢动物的觅食模式已经发生变化，以应对栖息地多样性的丧失和猎物资源的相应变化。