Fine-scale genetic structure and infection of (Diptera: Culicidae) in Nanjing city, China.

is an indigenous primary vector of dengue and Zika viruses in China. is a gram-negative and common intracellular bacteria, which is maternally inherited endosymbionts and could expand their propagation in host populations by means of various manipulations. Compared with research on the dispersion of at the macrospatial level (mainly at the country or continent level), little is known about its variation and infection at the microspatial level, which is essential for its management. Meanwhile, no local cases of dengue fever have been recorded in the history of Nanjing, which implies that few adulticides have been applied in the city. Thus, the present study examines how the population varies and the infection status of each population among microspatial regions of Nanjing City. The genetic structure of 17 populations collected from urban, urban fringe, and rural regions of Nanjing City was investigated based on 9 microsatellite loci and the mitochondrial gene. The infection status of each population was also assessed with A- and B-specific primers. Nine out of 58 tested pairs of microsatellite markers were highly polymorphic, with a mean PIC value of 0.560, and these markers were therefore chosen for microsatellite genotyping analysis. The Na value of each population was very high, and the urban area populations (7.353 ± 4.975) showed a lower mean value than the urban fringe region populations (7.866 ± 5.010). A total of 19 haplotypes were observed among 329 individuals via haplotype genotyping, with the highest diversity observed among the urban fringe populations (Hd = 0.456) and the lowest among the urban populations (Hd = 0.277). Each population showed significant departure from HWE, and significant population expansion was observed in only three populations from the urban (ZSL), urban fringe (HAJY), and rural areas (HSZY) ( < 0.05). Combined with DAPC analysis, all the populations were adequately allocated to two clades with significant genetic differences according to population structure analysis, and the best K value was equal to two. AMOVA results showed that most (96.18%) of the genetic variation detected in occurred within individuals (F = 0.22238, < 0.0001), while no significant positive correlation was observed via isolation by distance (IBD) analysis ( = 0.03262, = 0.584). The TCS network of all haplotypes showed that haplotype 1 (H1) and haplotype 4 (H4) were the most frequent haplotypes among all populations, and the haplotype frequency significantly increased from urban regions (36.84%) to rural regions (68.42%). Frequent migration was observed among populations from rural to urban regions via the urban fringe region, with four direct migration routes between rural and urban regions. Furthermore, genotyping results showed that most of the individuals of each population were coinfected with A and B. The independent infection rate of A was slightly higher than that of B, and no significant differences were observed among different regions. In the microspatial environment of Nanjing City, the urban fringe region is an important region for the dispersion of populations between rural and urban areas, and A and B coinfection is the most common infection status in all populations among different regions.