Data from: Higher flight activity in the offspring of migrants compared to residents in a migratory insect

Migration has evolved among many animal taxa and migratory species are found across all major lineages. Insects are the most abundant and diverse terrestrial migrants, with trillions of animals migrating annually. Partial migration, where populations consist of resident and migratory individuals, is ubiquitous among many taxa. However, the underlying mechanisms are relatively poorly understood and may be driven by physiological, behavioural or genetic variation within populations. We investigated the differences in migratory tendency between migratory and resident phenotypes of the hoverfly, Episyrphus balteatus, using tethered flight mills. Further, to test whether migratory flight behaviour is heritable and disentangle the effects of environment during development, we compared the flight behaviour of laboratory-reared offspring of migrating, overwintering and summer animals. Offspring of migrants initiated more flights than those of resident individuals. Interestingly, there were no differences among wild-caught phenotypes with regard to number of flights or total flight duration. Low activity in field-collected migrants might be explained by an energy conserving state that migrants enter in to when under laboratory conditions, or a lack of suitable environmental cues for triggering migration. Our results strongly suggest that flight behaviour is heritable and that genetic factors influence migratory tendency in E. balteatus. These findings support the growing evidence that genetic factors play a role in partial migration and warrant careful further investigation.

迁徙行为已在众多动物类群中演化而来，各大主要演化支系中均分布有迁徙物种。昆虫是数量最丰富、多样性最高的陆生迁徙动物，每年有万亿级个体参与迁徙。部分迁徙（partial migration）指种群由居留型与迁徙型个体共同构成的迁徙模式，在众多类群中广泛存在。然而其内在调控机制尚不甚明晰，可能由种群内的生理、行为或遗传差异所驱动。本研究以食蚜蝇（Episyrphus balteatus）的迁徙型与居留型表型为研究对象，利用悬尾飞行磨（tethered flight mills）探究二者在迁徙倾向上的差异。此外，为验证迁徙飞行行为是否具有可遗传性，并厘清发育阶段环境的影响，本研究比较了野外迁徙个体、越冬个体与夏季个体的实验室繁育后代的飞行行为。结果显示，迁徙型个体的后代发起飞行的次数显著多于居留型个体的后代。值得注意的是，野外捕获的不同表型个体在飞行次数与总飞行时长上并无显著差异。野外捕获的迁徙个体活动水平较低，这一现象可通过两种机制解释：一是迁徙个体在实验室环境下进入能量节约状态，二是缺乏触发迁徙的适宜环境信号。本研究结果强烈表明，食蚜蝇的飞行行为具有可遗传性，且遗传因素会影响其迁徙倾向。这些发现为‘遗传因素在部分迁徙中发挥作用’这一日益增多的研究证据提供了支撑，同时也有待后续开展更深入的细致研究。