Host-plant dependent population genetics of the invading weevilHypera postica

Abstract

Population genetics of invading pests can be informative for understanding their ecology. In this study, we investigated population genetics of the invasive alfalfa weevil Hypera postica in Fukuoka Prefecture, Japan. We analyzed mitochondrial tRNALeu-COII, nuclear EF-1α gene fragments, and Wolbachia infection in relation to three leguminous host plants: Vicia angustifolia, Vicia villosa, and a new host Astragalus sinicus cultivated as a honey source and green manure crop. A parsimony network generated from mitochondrial gene sequences uncovered two major haplotypic groups, Western and Egyptian. In contrast to reported Wolbachia infection of the Western strain in the United States, none of our analyzed individuals were infected. The absence of Wolbachia may contribute to the stable coexistence of mitochondrial strains through inter-strain reproductive compatibility. Hypera postica genetic variants for the mitochondrial and nuclear genes were associated neither with host plant species nor with two geographic regions (Hisayama and Kama) within Fukuoka. Mitochondrial haplogroups were incongruent with nuclear genetic variants. Genetic diversity at the nuclear locus was the highest for the populations feeding on V. angustifolia. The nuclear data for A. sinicus-feeding populations indicated past sudden population growth and extended Bayesian skyline plot analysis based on the mitochondrial and nuclear data showed that the growth of A. sinicus-feeding population took place within the past 1000 years. These results suggest a shorter history of A. sinicus as a host plant compared with V. angustifolia and a recent rapid growth of H. postica population using the new host A. sinicus.

New haplotype and inter‐strain reproductive compatibility ofWolbachia‐uninfected alfalfa weevil,Hypera postica(Coleoptera:Curculionidae), inJapan

“…; for populations in Japan, Iwase et al . ). Furthermore, in the USA, the Western strain is infected with Wolbachia , which causes reproductive incompatibility in inter‐strain crosses (Blickenstaff ; White et al .…”

“…PCRs were performed following Iwase et al . (). As a positive control, we used Callosobruchus chinensis (L.) that was naturally infected with Wolbachia (Kondo et al .…”

“…; Iwase et al . ). Although the pupation and aestivation sites are different among strains, they probably encounter each other when they feed on their common host plants.…”

“…Recently, we found that the Japanese Western strain from Fukuoka populations in northern Kyushu was uninfected with Wolbachia (Iwase et al . 2015a,b).…”

“…), toothed medic Medicago polymorpha L., and recently reported Chinese milk vetch Astragalus sinicus L., one of the most important honey resources for humans and green manure for rice. Hypera postica has become a serious pest in the apiculture industry (Okumura 1991;Kuwata et al 2005), reaching higher densities on A. sinicus than on other host plants (Iwase et al 2015a).…”