Population Genetic Structure Of Adelphocoris Suturalis(Hemiptera:Miridae) In China

The plant bug, Adelphocoris suturalis (Jakovlev,1882)(Hemiptera:Miridae), is a widespread pest in East Asia (e.g. China, Korea, Russia and Japan). In China, with areawide cultivation of transgenic Bt cotton, A. suturalis has become a dominant pests. As a highly polyphagous insect, A. suturalis can attack a variety of plants (-115species, primarily cotton). It causes significant economic losses, and reduces yields and qualities of crops. In addition, this insect may easily reach outbreak threshold, switch host crops, or experience geographic spread because of its great tolerance to climate change, high population growth rate, and strong dispersal capacity.The previous studies on this pest were mainly focused on its morphology, ecology and management. However, its phylogeography and population structure remains poorly understood. In this study, we systematic analysis of the phylogeographic structure, phylogeographic history, and dispersal pathways for this species, which from China and Japan, using three mitochondrial genes (mtDNA) and nuclear internal transcribed spacer (rDNA ITS) region. The main results as followings:(1) In this study,419sequences were obtained successfully from COI, CYTB and ND5genes, respectively, and406sequences from ITS markers were used in the subsequent analysis. The length of COI, CYTB, ND5and ITS sequences alignment were603bp,789bp,654bp and1303bp [including5.8S (123bp), ITS2(1096bp) and28S (84bp)] respectively.107polymorphic sites and95haplotypes were found among all sequences of combined mitochondrial DNA.125polymorphic sites and130haplotypes were found when gaps were treated as fifth state.125haplotypes and122polymorphic sites were found when gaps were treated as missing. In a word, high levels of haplotype diversity and low levels of nucleotide diversity were found in all populations.(2) Phylogeographic structure showed significant genetic differentiation among central China, peripheral China and Japanese populations. The genetic discontinuity analysis suggested that the geographic barriers were resulted in the genetic differentiation among three regions. High levels of gene flow were found among all populations, however, the small Nem values and high levels of gene flow were observed in seven peripheral populations, which implied that inbreeding within a population occurred more frequent and severe among these populations and physical barriers hindered gene flow.(3) Phylogeographic analysis of haplotypes showed that two clades were formed; one clade comprised populations from central China and the other clade comprised populations from peripheral China; most Japanese haplotypes were grouped together and separated from central China haplotypes. In the haplotype network, H11was the major haplotype of peripheral China and HI5was the major haplotype of central China, the two haplotypes were located at the center of the network and have more widespread distributions, which formed two star-shaped network. The network suggested that A. suturalis experienced population expansion events in China.(4) Neutrality test showed Fu’s Fs, Fu and Li’s D and Fu and Li’s F were significant negative values, mismatch distribution analysis showed unimodal map, and Bayesian skyline plot analysis, all of which showed A. suturalis experience a rapid population growth in China. Population expansion occurred during the transition from Last Interglacial (LIG) to Last Glacial Maximum (LGM).