While global change research has greatly expanded in recent years, it remains unclear how environmental change will impact the mobility of many organisms. Flight is an important mode of transportation that affects ecological functions, including mate location, foraging, and migration. However, the effects of increasing temperature and diet quality on flight remain largely unknown. Here, we explore the effects of rearing temperature and larval diet quality on the flight ability of an iconic and ecologically threatened migratory insect, the monarch butterfly, Danaus plexippus. Monarch larvae were reared at two temperatures (25 °C and 28 °C) and on three milkweed species with varying phytochemistry (Asclepias incarnata, Asclepias syriaca, and Asclepias curassavica) in a fully factorial experiment. We tested flight ability using an automated flight mill, which measured cumulative flight distance, duration, and instantaneous velocity. Higher rearing temperatures reduced monarch flight ability, and larval diet quality influenced forewing morphology. Dietary milkweed with higher cardenolide concentrations (A. curassavica) induced shorter, wider forewings whereas milkweed with low to intermediate cardenolides (A. incarnata and A. syriaca) induced longer, narrower forewings, which are considered better for gliding flight used during migration. Our results provide evidence that projected increases in temperature and the subsequent expansion of tropical milkweed (A. curassavica) into the central breeding range of eastern North American migratory monarchs could reduce migration success. Further research is needed to identify mechanisms explaining the effects of diet and temperature on monarch flight ability and fitness, to ensure that appropriate conservation strategies are employed to preserve migratory populations.

中文翻译：

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饮食和温度对帝王蝶翅膀形态和飞行能力的影响

尽管近年来全球变化研究已大大扩展，但环境变化将如何影响许多生物的移动性仍不清楚。飞行是影响生态功能的重要运输方式，包括配偶位置、觅食和迁徙。然而，温度升高和饮食质量对飞行的影响在很大程度上仍然未知。在这里，我们探讨了饲养温度和幼虫饮食质量对标志性和生态受到威胁的迁徙昆虫帝王蝶 Danaus plexippus 飞行能力的影响。帝王幼虫在两种温度（25°C 和 28°C）下饲养，并在完全析因实验中用三种具有不同植物化学成分的乳草（马利筋属植物、马利筋属syriaca 和 Asclepias curassavica）饲养。我们使用自动飞行磨机测试飞行能力，它测量累积飞行距离、持续时间和瞬时速度。较高的饲养温度降低了帝王蝶的飞行能力，幼虫的饮食质量影响了前翅形态。具有较高cardenolide浓度的日粮马利筋（A. curassavica）诱导更短、更宽的前翅，而具有低到中等cardenolides（A. incarnata和A. syriaca）的马利筋诱导更长、更窄的前翅，这被认为更适合在迁徙期间使用的滑翔飞行。我们的结果提供的证据表明，预计温度升高以及随后热带乳草（A. curassavica）向北美东部迁徙君主的中心繁殖范围扩张可能会降低迁徙成功率。