The genetic trail of the invasive mosquito species Aedes koreicus from the east to the west of Northern Italy

Background: Aedes koreicus is native to Far East Asia and recorded in Europe since 2008. In Italy, Ae. koreicus is widespread throughout the Northern part of the peninsula, highlighting its invasive potential and spread. However, no clear clues about the dispersal patterns of the species have been collected so far. Methodology/Principal findings: Population genetic analyses were performed to assess the genetic structure of populations of Ae. koreicus and to make hypotheses about its dispersal patterns in Northern Italy. Ten microsatellite markers specific for Ae. koreicus were used to genotype 414 individuals from 13 populations in the pre-alpine area of Italy, and neighboring Slovenia. Basic and Bayesian population genetic analyses were performed to evaluate patterns of genetic variation, genetic structure, and demography of selected mosquito populations. While presenting a certain degree of structuring, the Italian and Slovenian populations of Ae. koreicus were poorly differentiated. Moreover, demographic analysis supports the expansion of a single population propagule of Ae. koreicus in Italy and Slovenia and provides evidence of the presence of overwintering populations in the studied area. Conclusions/Significance: Our results highlight a common origin, and stable colonization of Northern Italy and Slovenia, as a probable consequence of the expansion of a unique population. This stresses out the importance of continuous monitoring of Ae. koreicus, to finally uncover the geographic origins and entrance pathways of invasive populations and to prevent or limit further introductions. Author summary: In the present manuscript, the population genetics of the invasive mosquito Aedes koreicus is presented. Specifically, 13 invasive (Italy, Slovenia) and one native (Republic of Korea, ROK) populations have been analyzed, with a particular focus on individuals from Northern Italy, an area where a widespread presence of the mosquito species has been observed. Results revealed a low variability in populations from non-endemic countries, even when collected in different years. A stable colonization is thus highlighted. This is probably the consequence of a single event of importation, as supported by demographic analysis. Individuals from the ROK mainland here analyzed are not the source of this introduction, being genetically unrelated to the Italian and Slovenian individuals. This research provided novel data for the investigation of the pattern of expansion of Ae. koreicus in Northern Italy, and thus pose important basis for future studies of the invasive corridors of the species to limit/prevent its further dispersion.