Abstract :
[en] Sitobion miscanthi (Takahashi), a wheat aphid, is an economically damaging aphid pest and the dominant species in China. Migration and diffusion are not only important manifestations of population dynamics, but also important ecological countermeasures for aphids to adapt to the environment. Migration, as the main physiological behavior characteristic of aphids, is the main reason for the difficulty in monitoring and forecasting. Temperature, wind and geographic location are the main abiotic factors for the migration of aphids. In this thesis, indoor and outdoor experiments were combined associated to methods of physiology and population genetics. Firstly, the physiological and reproductive parameters of different geographical populations of S. miscanthi at different temperatures and the life history traits of different populations during the growth and development period were investigated and analyzed. There was no significant difference in reproductive capacity within populations from northern China. In addition, latitude was positively correlated with aphids’ longevity. Secondly, eighteen geographical populations from China were studied by using one mitochondrial gene COI, one nuclear gene (EF-1α) and two endosymbiotic Buchnera genes (gnd and trpA). Two main natural migration pathways of S. miscanthi in China were observed: one was from Yunnan to the Sichuan Basin and another from Wuhan, Xinyang and Jiaodong Peninsula areas to the northwest. We inferred that these aphids appear first in the southwest and south regions and spread to the north with the help of the southeast and southwest monsoons, which occur in spring and summer. In autumn, aphids spread southward with the northeast and northwest monsoons. Finally, to clarify geographical structure of S. miscanthi in China and the factors affecting its distribution, we selected aphid samples from six geographic locations in China and analyzed the evolution history of genetic differentiation. Our 6 geographical populations of S. miscanthi were divided into three groups, Yinchuan, Suzhou, and other populations. Genetic structure analysis based on the mitochondrial (COI) and the symbiotic genes (gnd and trpA) were similar indicating that the symbiotic genes could act as potential molecular markers in studying the genetic structure and diversity of aphid populations. Difference in annual average temperature may be the reason for diversity genetic structure of S. miscanthi providing theoretical evidence of the aphid migration. It was speculated that S. miscanthi has seasonal migration patterns in wheat regions to allow prediction of potential aphids outbreaks in China.
