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Lygus pratensis (L.) is an important cotton pest in China, especially in the northwest region. Nymphs and adults cause serious quality and yield losses. However, the genetic structure and geographic distribution of L. pratensis is not well known. We analyzed genetic diversity, geographical structure, gene flow, and population dynamics of L. pratensis in northwest China using mitochondrial and nuclear sequence datasets to study phylogeographical patterns and demographic history. L. pratensis (n = 286) were collected at sites across an area spanning 2,180,000 km2, including the Xinjiang and Gansu-Ningxia regions. Populations in the two regions could be distinguished based on mitochondrial criteria but the overall genetic structure was weak. The nuclear dataset revealed a lack of diagnostic genetic structure across sample areas. Phylogenetic analysis indicated a lack of population level monophyly that may have been caused by incomplete lineage sorting. The Mantel test showed a significant correlation between genetic and geographic distances among the populations based on the mtDNA data. However the nuclear dataset did not show significant correlation. A high level of gene flow among populations was indicated by migration analysis; human activities may have also facilitated insect movement. The availability of irrigation water and ample cotton hosts makes the Xinjiang region well suited for L. pratensis reproduction. Bayesian skyline plot analysis, star-shaped network, and neutrality tests all indicated that L. pratensis has experienced recent population expansion. Climatic changes and extensive areas occupied by host plants have led to population expansion of L. pratensis. In conclusion, the present distribution and phylogeographic pattern of L. pratensis was influenced by climate, human activities, and availability of plant hosts.

The complete mitochondrial (mt) genome of the plant bug, Apolygus lucorum, an important cotton pest, has been sequenced and annotated in this study. The entire circular genome is 14 768 bp in size and represents the smallest in presently known heteropteran mt genomes. The mt genome is encoding for two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, 13 protein coding genes and a control region, and the order, content, codon usage and base organization show similarity to a great extent to the hypothetical ancestral model. All protein coding genes use standard initiation codons ATN. Conventional stop codons TAA and TAG have been assigned to the most protein coding genes; however, COIII, ND4 and ND5 genes show incomplete terminator signal (T). All tRNA genes possess the typical clover leaf structure, but the dihydrouridine arm of tRNA(Ser(AGN)) only forms a simple loop. Secondary structure models of rRNA genes are generally in accordance with the former models, although some differences exist in certain parts. Three intergenic spacers have never been found in sequenced mt genomes of Heteroptera. The phylogenetic study based on protein coding genes is largely congruent with previous phylogenetic work. Both Bayesian inference and maximum likelihood analyses highly support the sister relationship of A. lucorum and Lygus lineolaris, and Miridae presents a sister position to Anthocoridae., (© 2013 Institute of Zoology, Chinese Academy of Sciences.)