Population genetic structure and expansion patterns of the cotton pest Adelphocoris fasciaticollis

Understanding the population genetic structure and demographic dynamics of important agricultural pest insects is very important in studying insecticide resistance and control strategies. The plant bug Adelphocoris fasciaticollis (Reuter) (Hemiptera: Miridae) is one of the main insect pests on cotton in Northern China. We studied large-scale genetic structure and genetic diversity patterns and explored the demographic history. We also employed a phylogeographical approach on A. fasciaticollis samples using sequence data from mitochondrial DNA (mtDNA) and nuclear DNA (ncDNA). MtDNA showed a significant correlation between genetic and geographical distances, but ncDNA did not support this correlation. Both datasets revealed that A. fasciaticollis populations had experienced recent expansion and lacked a geographical structure. One reason for lack of a genetic structure is a high level of gene flow among the populations. We suggest that the strong flight capability of A. fasciaticollis has been aided by the East Asian monsoon and cold fronts to accelerate the rate of range expansion. In addition, decreased insecticide usage and disturbances from human activities may all have contributed to population expansion. The low effective population number was based on two datasets. It is suggested that the host crop use, local climate conditions, and the recent population expansion might be the main influencing factors.