title: Unexpected patterns of admixture in German populations of Aedes japonicus japonicus (Diptera: Culicidae) underscore the importance of human intervention.
abstract: The mosquito Aedes japonicus japonicus, originally restricted to temperate East Asia, is now widespread in North America and more recently has become established in Europe. To ascertain the putative number of separate introductions to Europe and examine patterns of expansion we analyzed the genetic makeup of Ae. j. japonicus populations from five cemeteries in North Rhine-Westphalia and Rhineland-Palatinate, two western German federal states, as well as of specimens from populations in Belgium, Switzerland, and Austria/Slovenia. To do so, we genotyped individual specimens at seven pre-existing polymorphic microsatellite loci and sequenced part of the nad4 mitochondrial locus. We found evidence of two different genotypic signatures associated with different nad4 mitochondrial haplotypes, indicating at least two genetically differentiated populations of Ae. j. japonicus in Europe (i.e. two distinct genotypes). Belgian, Swiss, and Austrian/Slovenian populations all share the same genotypic signature although they have become differentiated since isolation. Contrary to expectations, the German Ae. j. japonicus are not closely related to those in Belgium which are geographically nearest but are also highly inbred. German populations have a unique genotype but also evidence of mixing between the two genotypes. Also unexpectedly, the populations closest to the center of the German infestation had the highest levels of admixture indicating that separate introductions did not expand and merge but instead their expansion was driven by punctuated human-mediated transport. Critically, the resulting admixed populations have higher genetic diversity and appear invasive as indicated by their increased abundance and recent spread across western Germany.
authors.affiliation: Leibniz-Centre for Agricultural Landscape Research, Müncheberg, Germany.
authors.forename: Dorothee E
authors.initials: DE
authors.lastname: Zielke
authors.affiliation: Leibniz-Centre for Agricultural Landscape Research, Müncheberg, Germany.
authors.forename: Doreen
authors.initials: D
authors.lastname: Werner
authors.affiliation: National Centre for Vector Entomology, Institute of Parasitology, University of Zurich, Zurich, Switzerland; Avia-GIS, Zoersel, Belgium.
authors.forename: Francis
authors.initials: F
authors.lastname: Schaffner
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald - Insel Riems, Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Kampen
authors.affiliation: Center for Vector Biology and Department of Entomology, Rutgers University, New Brunswick, New Jersey, United States of America.
authors.forename: Dina M
authors.initials: DM
authors.lastname: Fonseca
mesh_terms: D000330:Aedes / Q000235:genetics*; D000818:Animals; D056426:Genetic Loci; D005838:Genotype; D005858:Germany; D006801:Humans; D058865:Introduced Species; D018895:Microsatellite Repeats