The diamondback moth Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is one of the most destructive insect pests of cruciferous plants worldwide. Biological, ecological and genetic studies have indicated that this moth is migratory in many regions around the world. Although outbreaks of this pest occur annually in China and cause heavy damage, little is known concerning its migration. To better understand its migration pattern, we investigated the population genetic structure and demographic history of the diamondback moth by analyzing 27 geographical populations across China using four mitochondrial genes and nine microsatellite loci. The results showed that high haplotype diversity and low nucleotide diversity occurred in the diamondback moth populations, a finding that is typical for migratory species. No genetic differentiation among all populations and no correlation between genetic and geographical distance were found. However, pairwise analysis of the mitochondrial genes has indicated that populations from the southern region were more differentiated than those from the northern region. Gene flow analysis revealed that the effective number of migrants per generation into populations of the northern region is very high, whereas that into populations of the southern region is quite low. Neutrality testing, mismatch distribution and Bayesian Skyline Plot analyses based on mitochondrial genes all revealed that deviation from Hardy-Weinberg equilibrium and sudden expansion of the effective population size were present in populations from the northern region but not in those from the southern region. In conclusion, all our analyses strongly demonstrated that the diamondback moth migrates within China from the southern to northern regions with rare effective migration in the reverse direction. Our research provides a successful example of using population genetic approaches to resolve the seasonal migration of insects.

Population genetic structure and approximate Bayesian computation analyses reveal the southern origin and northward dispersal of the oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae) in its native range AbstractThe oriental fruit moth (OFM) Grapholita molesta is one of the most destructive orchard pests. Assumed to be native to China, the moth is now distributed throughout the world. However, the evolutionary history of this moth in its native range remains unknown. In this study, we explored the population genetic structure, dispersal routes and demographic history of the OFM in China and South Korea based on mitochondrial genes and microsatellite loci. The Mantel test indicated a significant correlation between genetic distance and geographical distance in the populations. Bayesian analysis of population genetic structure (BAPS) identified four nested clusters, while the GENELAND analysis inferred five genetic groups with spatial discontinuities. Based on the approximate Bayesian computation approach, we found that the OFM was originated from southern China near the Shilin area of Yunnan Province. The early divergence and dispersal of this moth was dated to the Penultimate glaciation of Pleistocene. Further dispersal from southern to northern region of China occurred before the last glacial maximum, while the expansion of population size in the derived populations in northern region of China occurred after the last glacial maximum. Our results indicated that the current distribution and structure of the OFM were complicatedly influenced by climatic and geological events and human activities of cultivation and wide dissemination of peach in ancient China. We provide an example on revealing the origin and dispersal history of an agricultural pest insect in its native range as well as the underlying factors.

The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae) currently is one of the economically most destructive pest species of stone and pome fruits worldwide. Here we sequenced the complete mitochondrial genome of this pest. This genome is 15,776 bp long, with an A + T content of 81.24%, containing 37 typical animal mitochondrial genes and an A + T-rich region. All gene are arranged as hypothesized ancestral gene order of insects except for trnM, which was shuffled from 3′ downstream of trnQ to 5′ upstream of trnI. cox1 gene uses unusual CGA start codon, as that in all other sequenced lepidopteran mitochondrial genome. The secondary structures for the two rRNA genes were predicted. All helices typically present in insect mitochondrial rRNA genes are generated. A microsatellite sequence was inserted into the region of H2347 in rrnL in G. molesta and two other sequenced tortricid mitochondrial genomes, indicating that the insertion event in this helix might occurred anciently in family Tortricidae. All of the 22 typical animal tRNA genes have a typical cloverleaf structure except for trnS2, in which the D-stem pairings in the DHU arm are absent. An intergenic sequence is present between trnQ and nad2 as well as in other sequenced lepidopteran mitochondrial genomes, which was presumed to be a remnant of trnM gene and its boundary sequences after the duplication of trnM to the upstream of trnI in Lepidoptera. The A + T-rich region is 836 bp, containing six repeat sequences of “TTATTATTATTATTAAATA(G)TTT.”Electronic supplementary materialThe online version of this article (doi:10.1007/s11033-011-1049-y) contains supplementary material, which is available to authorized users.

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Here we determined the mitochondrial genome sequence of a notorious pest, the diamondback moth Plutella xylostella (Lepidoptera: Yponomeutoidea: Plutellidae). The mitochondrial genome contains 37 typical animal mitochondrial genes and an A+T-rich region. The gene arrangement is identical to that of other ditrysian lepidopteran mitochondrial genomes, but different from the ancestral gene arrangement in the non-ditrysian Hepialidae of Lepidoptera. The start codon of the cox1 gene is CGA, which is dissimilar to its homologs in most other insects. In Lepidoptera, cox1 and cox2 have low nucleotide diversities, while the nad6, nad2, and nad3 genes are highly variable. Phylogenetic analyses uncovered the reciprocal monophyly of Ditrysia, Apoditrysia, Obtectomera, and Macrolepidoptera, and the placement of the Hesperiidae within Papilionoidea. Our analyses suggest that the complete mitochondrial genome sequences are a promising marker toward fully resolving the phylogenetic relationships within Lepidoptera.

The complete nucleotide sequence of the mitochondrial genome of Macrotermes barneyi Light (Isoptera: Termitidae) was determined. This mitochondrial genome is 15,940 bp with 37 typical animal mitochondrial genes and an A+T-rich region. Gene positions and directions are identical to that of the pupative ancestral arrangement of insects. All protein-coding genes start with ATN codon. Seven protein-coding genes stop with termination codon TAA. Four protein-coding genes use incomplete stop codons TA and two use T. The base composition of M. barneyi mitochondrial genome is normal to most insects. All of the 22 tRNA genes, ranging from 63 to 76 bp, have a typical cloverleaf structure except for trnS2. In trnS2, D-stem pairings in the DHU (dihydrouridine) arm is absent as in many sequenced insect species. Five elements characterized by A+T-rich region of the insect mitochondrial genome are found on their conserved arrangement. However, no repeat sequence is present on the downstream of the A+T-rich region.

The complete mitochondrial genome of the summer fruit tortrix moth Adoxophyes orana (Lepdioptera: Tortricidae) was determined (GenBank accession No. JX872403). The genome is 15,343 bp long with 37 typical animal mitochondrial genes and an A+T-rich region. As in other sequenced mitochondrial genomes of Lepidoptera, trnM was rearranged to the upstream of trnI-trnQ-trnM cluster compared with the pupative ancestral arrangement of insects. All protein-coding genes start with ATN start codon except for the gene cox1, which uses CGA start codon as in other lepidopteran species. Eight protein-coding genes stop with termination codon TAA. Five protein-coding genes use incomplete stop codons T. The A+T-region is located between rrnS and trnM with a length of 331 bp. This is the fifth completely sequenced mitochondrial genome from the family Tortricidae.

The complete mitochondrial genome of the codling moth Cydia pomonella (Lepidoptera: Tortricidae) was determined. The genome is 15,253 bp long with 37 typical animal mitochondrial genes and an A+T-rich region. All genes are arranged in their conserved positions compared with the pupative ancestral arrangement of insects except for trnM, which was translocated to the upstream of the transfer RNA cluster trnI-trnQ as in all previously reported lepidopteran mitochondiral genomes. Seven portein-coding genes use ATG start codon and five use ATT. However, the cox1 gene uses the CGA start codon as it is found in all previous reported mitochondrial genomes of Lepidoptera. Nine protein-coding genes stop with termination codon TAA. Four protein-coding genes use incomplete stop codons TA or T. The A+T region is located between rrnS and trnM with a length of 331 bp.