Genetic structure and diversity of a newly invasive species, the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) in China

Cydia pomonella (L.) was firstly reported in China in the 1950s and considered as one of the most serious invasive pest in fruit orchards of China. It spread rapidly from the original site in Xinjiang to other northwestern regions. The pest has further penetrated northeastern China since 2006. With its rapid invasion rate, most pome fruit production areas of China are being threatened. As yet there has been no research into the genetic diversity and structure of the codling moth population in China. We investigated the genetic variations of 12 C. pomonella populations collected from the main distribution regions (Xinjiang, Gansu and Heilongjiang Provinces) in China and compared them with one German and one Swiss population using eight microsatellites loci to infer the characteristics of genetic diversity and genetic structure. We observed sequential loss of genetic diversity and significant structuring associated with distribution but no significant correlation between genetic distance and geographic distance among northwestern populations. There was no genetic evidence for bottleneck effects in any of the populations. The results suggest that the loss of genetic diversity in C. pomonella populations resulted from the successive colonization of founder populations. Recent invasion history led to the lack of any bottleneck effect. The high level of population genetic structuring is related to the weak flight capacity of the codling moth and the human-aided dispersal rather than to geographic distance. These genetic data not only provide us with an understanding of the micro-evolutionary processes related to successful biological invasions, but also provide guidance for pest management strategies.