title: Recently discovered Aedes japonicus japonicus (Diptera: Culicidae) populations in The Netherlands and northern Germany resulted from a new introduction event and from a split from an existing population.
abstract: BACKGROUND
  Originally native to East Asia, Aedes japonicus japonicus, a potential vector of several arboviruses, has become one of the most invasive mosquito species in the world. After having established in the USA, it is now spreading in Europe, with new populations emerging. In contrast to the USA, the introduction pathways and modes of dispersal in Europe are largely obscure.
  
  
  METHODS
  To find out if two recently detected populations of Ae. j. japonicus in The Netherlands and northern Germany go back to new importations or to movements within Europe, the genetic makeup of mosquito specimens from all known European populations was compared. For this purpose, seven microsatellite loci from a representative number of mosquito specimens were genotyped and part of their mitochondrial nad4 gene sequenced.
  
  
  RESULTS
  A novel nad4 haplotype found in the newly discovered Dutch population of Ae. j. japonicus suggests that this population is not closely related to the other European populations but has emanated from a further introduction event. With five nad4 haplotypes, the Dutch population also shows a very high genetic diversity indicating that either the founder population was very large or multiple introductions took place. By contrast, the recently detected North German population could be clearly assigned to one of the two previously determined European Ae. j. japonicus microsatellite genotypes and shows nad4 haplotypes that are known from West Germany.
  
  
  CONCLUSIONS
  As the European populations of Ae. j. japonicus are geographically separated but genetically mixed, their establishment must be attributed to passive transportation. In addition to intercontinental shipment, it can be assumed that human activities are also responsible for medium- and short-distance overland spread. A better understanding of the processes underlying the introduction and spread of this invasive species will help to increase public awareness of the human-mediated displacement of mosquitoes and to find strategies to avoid it.
authors.affiliation: Institute for Land Use Systems, Leibniz-Centre for Agricultural Landscape Research, Eberswalder Straße 84, 15374, Muencheberg, Germany. zielke@zalf.de.
authors.forename: Dorothee E
authors.initials: DE
authors.lastname: Zielke
authors.affiliation: National Centre for Monitoring of Vectors, Netherlands Food and Consumer Product Safety Authority, Ministry of Economic Affairs Wageningen, Wageningen, The Netherlands. a.ibanezjusticia@minlnv.nl.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Ibáñez-Justicia
authors.affiliation: University of Primorska, Koper, Slovenia. katja.kalan@zrs.upr.si.
authors.forename: Katja
authors.initials: K
authors.lastname: Kalan
authors.affiliation: University of Osijek, Osijek, Croatia. enrih@biologija.unios.hr.
authors.forename: Enrih
authors.initials: E
authors.lastname: Merdić
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Insel Riems, Greifswald, Germany. helge.kampen@fli.bund.de.
authors.forename: Helge
authors.initials: H
authors.lastname: Kampen
authors.affiliation: Institute for Land Use Systems, Leibniz-Centre for Agricultural Landscape Research, Eberswalder Straße 84, 15374, Muencheberg, Germany. doreen.werner@zalf.de.
authors.forename: Doreen
authors.initials: D
authors.lastname: Werner
mesh_terms: D000330:Aedes / Q000235:genetics* / Q000502:physiology*; D063147:Animal Distribution / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D005838:Genotype; D005858:Germany; D006239:Haplotypes / Q000235:genetics; D058865:Introduced Species; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D009426:Netherlands; D025341:Principal Component Analysis; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial