Studies On Genetic Diversity And Migration Trajectory Of Different Geographic Populations Of The Meadow Moth, Loxostege Sticticalis (Lepidoptera: Pyralidae)

The meadow moth, Loxostege sticticalis L. (Lepidoptera: Pylaridae), is an important migrant pest of cash crops and food crops in the north, northeast and northwest of China. Great yield losses were resulted in due to the voracious feeding of larvae in the outbreak seasons. With the meadow moth population beginning to increase from 1995, there is coming the 3^rd outbreak after the foundation of the People's Republic of China. During this outbreak, L. sticticalis's occurrence presented some distinct characteristics, such as prolonged injury period, earlier occurrence, shortened larval instars, and aggravated harm to the crops, etc. The meadow moth mostly occurred in the remote and undeveloped areas, where the techniques of inspection and control were lagged and the ability to deal with the outbreak was limited. Therefore, it's of great importance to enhance the forecast ability. Migration is one of the most primary physiological and behavioral characteristics of the meadow moth, and also the major cause for the outbreak because it makes the population more difficult to forecast and control. Rader observation and flight simulation were used by previous researchers to study the migration of the moth, but it is still not enough clear about its migration, especially the potential routes.In this study, AFLP technique, followed by the detection using the silver staining systems, has been used to explore the genetic diversity of the 1st and hibernation generation of L. sticticalis, with 88 individuals of the moth collected from 11 geographic regions in China for each generation. The results indicated that both of the two generations were rich in the genetic diversity, much more of which came from different individuals within the population than that from different geographic populations, i.e., different geographic populations had much less genetic differentiation. Cluster analyses based on genetic similarities were performed to graphically display groupings between individuals. The results showed that L. sticticalis individuals of different geographic populations were mostly grouped together, disrelated to their locations, and genetic differentiation between geographic populations was also not obvious, which provided proof for the migration of L. sticticalis that resulted in frequent gene exchange between different populations. The moths from the hibernation areas of north China were proposed to migrate to the northeast of China in spring. After bred for one generation therein, parts of the adult might migrate back to the hibernation areas again.The possible routes of the migrant populations of L. sticticalis in northern China in the 3^rd outbreak were investigated by trajectory analysis. The trajectories were estimated by HYSPLIT, a model developed by NOAA. The results showed that possible source areas of the immigrants of the 1st generation into Zhangjiakou, Hebei Province were from the southeast of Mongolia and border areas between China and Mongolia. The immigrants of the 2nd generations into northern China were mostly from Wumeng and Eerduosi in Inner Mongolia and the southeast of Mongolia. The outbreak of the 1st generation in the northeast of China in 2004 mainly came from northern China. Thus, we propose that the source areas of L. sticticalis immigrants in China in this outbreak are composed of the following three parts, (â…°) hibernation areas in northern China, (â…±) the southeast of Mongolia and border areas between China and Mongolia, (â…²) the northeast of China. The latter two are just complementary to the source areas, but are indeed the necessary parts contributed to the outbreak of L. sticticalis.For the first time, we applied the molecular mark AFLP and the tool of trajectory analysis HYSPLIT to investigate the source areas of L. sticticalis migration. The results obtained helped to enrich our knowledge about L. sticticalis migration. However, high altitude areas and border areas with foreign lands are still blind areas of the study of migration, which need to be further studied.