Tracing Overseas Migration Using Strontium Isotope Analysis

Jim Crocker
15th November, 2024

Tracing Overseas Migration Using Strontium Isotope Analysis

Oriental armyworm (Mythimna separata)

Photo adapted from: Aalbert Rebergen / CC BY (Source)

Key Findings

  • The study by the National Agriculture and Food Research Organization, Japan, investigated the migration of the oriental armyworm, Mythimna separata, from China to Japan
  • Researchers used strontium isotope ratios to identify the origin of the insects, finding higher ratios in some individuals trapped in Japan, indicating they came from China
  • Trajectory analysis based on meteorological data supported the conclusion that these insects likely migrated from the East Asian continent, specifically from China
The oriental armyworm, Mythimna separata, is known for its seasonal migration from eastern to northeastern China, with some individuals potentially migrating overseas to Japan under specific meteorological conditions. A recent study by the National Agriculture and Food Research Organization, Japan, investigated this potential overseas migration using the immigrants' strontium radiogenic isotope ratio 87Sr/86Sr and backward flight trajectories from Japanese trapping sites[1]. The study aimed to determine whether some individuals of M. separata found in Japan originated from China. The researchers used the strontium isotope ratio 87Sr/86Sr as a geographical marker because it varies depending on the geological characteristics of different regions. By comparing the isotope ratios of Chinese-reared M. separata with those of insects reared in Japanese immigration areas, they found that the ratios of Chinese-reared M. separata were significantly higher. Some individuals trapped in western Japan had 87Sr/86Sr ratios higher than a statistical discriminating ratio, suggesting their origin in China. Additionally, the researchers conducted trajectory analysis, which involves calculating the possible flight paths of the insects based on meteorological data. This analysis indicated that the individuals with higher 87Sr/86Sr ratios might have originated from the East Asian continent, specifically the first-generation outbreak region in China and their migration waypoint regions. This study provides evidence for the direct or multistep overseas migration of M. separata from the East Asian continent to Japan. These findings offer new insights into the migration pathways and population dynamics of this pest, which is crucial for developing effective pest management strategies. The findings of this study are consistent with earlier research on the migration of other insect pests in East Asia. For instance, the migration of rice planthoppers, such as Laodelphax striatellus, Sogatella furcifera, and Nilaparvata lugens, has been well-documented[2]. These planthoppers have been known to migrate over long distances, spreading plant viruses across countries like China, Japan, and Korea. The ability to predict their migration has been developed by institutes in these countries, highlighting the importance of understanding insect migration for pest control. Furthermore, the study on M. separata aligns with previous research on the factors influencing insect migration. For example, environmental, physiological, hormonal, genetic, and molecular factors all play a role in the migration of M. separata[3]. The decision to migrate is facultative, meaning it depends on these factors. Understanding these influences is essential for predicting and managing the migration of this pest. In conclusion, the recent study by the National Agriculture and Food Research Organization, Japan, provides compelling evidence for the overseas migration of M. separata from China to Japan. By using strontium isotope ratios and trajectory analysis, the researchers have shed light on the migration pathways and population dynamics of this pest. These insights are crucial for developing effective pest management strategies and are supported by earlier research on the migration of other insect pests in East Asia and the factors influencing insect migration.

EnvironmentGeneticsAnimal Science

References

Main Study

1) Strontium isotope and trajectory method elucidating overseas migration of Mythimna separata to Japan.

Published 15th November, 2024

https://doi.org/10.1016/j.isci.2024.111160

Related Studies

2) Migration of rice planthoppers and their vectored re-emerging and novel rice viruses in East Asia.

https://doi.org/10.3389/fmicb.2013.00309

3) Regulation of migration in Mythimna separata (Walker) in China: a review integrating environmental, physiological, hormonal, genetic, and molecular factors.

https://doi.org/10.1603/EN10199


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