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Zhang B.,Qingdao Agricultural University | Nardi F.,University of Siena | Hull-Sanders H.,Pennsylvania State University | Wan X.,Sichuan Plant Protection Station | Liu Y.,Southwest University

The complete 16,043 bp mitochondrial genome (mitogenome) of Bactrocera minax (Diptera: Tephritidae) has been sequenced. The genome encodes 37 genes usually found in insect mitogenomes. The mitogenome information for B. minax was compared to the homologous sequences of Bactrocera oleae, Bactrocera tryoni, Bactrocera philippinensis, Bactrocera carambolae, Bactrocera papayae, Bactrocera dorsalis, Bactrocera correcta, Bactrocera cucurbitae and Ceratitis capitata. The analysis indicated the structure and organization are typical of, and similar to, the nine closely related species mentioned above, although it contains the lowest genome-wide A+T content (67.3%). Four short intergenic spacers with a high degree of conservation among the nine tephritid species mentioned above and B. minax were observed, which also have clear counterparts in the control regions (CRs). Correlation analysis among these ten tephritid species revealed close positive correlation between the A+T content of zero-fold degenerate sites (P0FD), the ratio of nucleotide substitution frequency at P0FD sites to all degenerate sites (zero-fold degenerate sites, two-fold degenerate sites and four-fold degenerate sites) and amino acid sequence distance (ASD) were found. Further, significant positive correlation was observed between the A+T content of four-fold degenerate sites (P 4FD) and the ratio of nucleotide substitution frequency at P 4FD sites to all degenerate sites; however, we found significant negative correlation between ASD and the A+T content of P4FD, and the ratio of nucleotide substitution frequency at P4FD sites to all degenerate sites. A higher nucleotide substitution frequency at non-synonymous sites compared to synonymous sites was observed in nad4, the first time that has been observed in an insect mitogenome. A poly(T) stretch at the 5′ end of the CR followed by a [TA(A)]n-like stretch was also found. In addition, a highly conserved G+A-rich sequence block was observed in front of the poly(T) stretch among the ten tephritid species and two tandem repeats were present in the CR. © 2014 Zhang et al. Source

Wan X.-W.,Southwest University | Liu Y.-H.,Southwest University | Luo L.-M.,Sichuan Plant Protection Station | Feng C.-H.,Sichuan Plant Protection Station | And 2 more authors.
Journal of Integrative Agriculture

Invasion of the oriental fruit fly, Bactrocera dorsalis, into new niches containing different food sources (a process referred to as host shift), may cause population genetic differentiation and sympatric speciation. To attempt to infer that experimentally, test populations were established by transferring a subset of the original populations, which had been grown on banana for many generations, onto navel orange, and then subculturing the navel orange population and banana population for at least 20 generations. Four pairs of SSR primers with high polymorphism on laboratory strains were used to detect population genetic differentiation. All six tested populations (the 5th, 10th and 15th generations of B. dorsalis fed on banana and navel orange, respectively) were found to have low genetic diversity. Furthermore, the genetic diversity of the navel orange populations was found to decline after being crossed for several generations. Populations initially were deviated from Hardy-Weinberg equilibrium, however, equilibrium was achieved with increasing numbers of generations in both of the host populations. Limited gene flows were found among the six populations. The Nei's standard genetic distances between the two host populations of the same generation were initially low, but increased with generation number. Genetic distances between banana and navel orange populations of the same generation were lower than genetic distances between different generations grown on the same host plant. Analysis of molecular distance (AMOVA) results based on generation groups and host groups demonstrated that genetic variation among generations was greater than that between the two host populations. The results indicated that population genetic differentiation occurred after the host shift, albeit at low level. Biogeography and taxonomy of the B. dorsalis complex revealed that speciation of B. dorsalis might be tightly associated with host shift or host specialization of B. dorsalis following dispersal. © 2014 Chinese Academy of Agricultural Sciences. Source

Wan X.W.,Southwest University | Liu Y.H.,Southwest University | Luo L.M.,Sichuan Plant Protection Station | Feng C.H.,Sichuan Plant Protection Station | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Biological invasions are a worldwide challenge, inducing losses of up to more than one trillion dollars (US) per annum. Having a detailed knowledge about the invasion process by following the invasive species from their source to their incursion areas i.e., their invasion history, may reveal the biological and ecological mechanisms that result in successful invasions. This information may assist researchers in finding effective controls. Applying molecular markers to the population genetics of an invasive species provides a new approach to investigate invasion history. Molecular methods have been applied to infer the invasion history, for example identifying the invasive species, the origin and pathway of the invader, reconstructing the colonization routes, analyzing the dispersal models, inferring the changes in the invasive alien species and the ecosystem effect on the regions invaded. Although the invasion processes of many species have been reconstructed using molecular makers, the reliability of these invasion history is debatable, because the inferred invasion scenarios may be affected by factors such as sampling range, type and the number of molecular markers used. © 2015, Ecological Society of China. All rights reserved. Source

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