Host-plant dependent population genetics of the invading weevil Hypera postica

AbstractPopulation genetics of invading pests can be informative for understandingtheirecology.Inthisstudy,weinvestigatedpopulationgeneticsoftheinvasivealfalfaweevil Hypera postica in Fukuoka Prefecture, Japan. We analyzed mitochondrialtRNA Leu -COII, nuclear EF-1α gene fragments, and Wolbachia infection in relationto three leguminous host plants: Vicia angustifolia, Vicia villosa, and a new hostAstragalus sinicus cultivated as a honey source and green manure crop. A parsimonynetwork generated from mitochondrial gene sequences uncovered two majorhaplotypicgroups,WesternandEgyptian.IncontrasttoreportedWolbachiainfectionof the Western strain in the United States, none of our analyzed individuals wereinfected. The absence of Wolbachia may contribute to the stable coexistence ofmitochondrial strains through inter-strain reproductive compatibility. Hypera posticagenetic variants for the mitochondrial and nuclear genes were associated neitherwith host plant species nor with two geographic regions (Hisayama and Kama)within Fukuoka. Mitochondrial haplogroups were incongruent with nuclear geneticvariants. Genetic diversity at the nuclear locus was the highest for the populationsfeeding on V. angustifolia. The nuclear data for A. sinicus-feeding populationsindicated past sudden population growth and extended Bayesian skyline plotanalysis based on the mitochondrial and nuclear data showed that the growth ofA. sinicus-feeding population took place within the past 1000 years. These resultssuggestashorterhistoryofA.sinicusasahostplantcomparedwithV.angustifoliaanda recent rapid growth of H. postica population using the new host A. sinicus.Keywords: Hypera postica, Chinese milk vetch, extended Bayesian skyline plot,statistical parsimony network, narrow-leaved vetch, hairy vetch