Pyrethroids are commonly used as mosquito adulticides and evolution of resistance to these compounds is a major threat to public health. 'Knockdown resistance' to pyrethroids (kdr) is frequently caused by nonsynonymous mutations in the voltage-gated sodium channel transmembrane protein (para) that reduce pyrethroid binding. Early detection of kdr is critical to the development of resistance management strategies in mosquitoes including Aedes aegypti, the most prevalent vector of dengue and yellow fever viruses. Brengues et al. described seven novel mutations in hydrophobic segment 6 of domain II of para in Ae. aegypti. Assays on larvae from strains bearing these mutations indicated reduced nerve sensitivity to permethrin inhibition. Two of these occurred in codons Iso1011 and Val1016 in exons 20 and 21 respectively. A transition in the third position of Iso1011 encoded a Met1011 replacement and a transversion in the second position of Val1016 encoded a Gly1016 replacement. We have screened this same region in 1318 mosquitoes in 32 additional strains; 30 from throughout Latin America. While the Gly1016 allele was never detected in Latin America, we found two new mutations in these same codons. A transition in the first position of codon 1011 encodes a Val replacement while a transition in the first position of codon 1016 encodes an Iso replacement. We developed PCR assays for these four mutations that can be read either on an agarose gel or as a melting curve. Selection experiments, one with deltamethrin on a field strain from Santiago de Cuba and another with permethrin on a strain from Isla Mujeres, Mexico rapidly increased the frequency of the Iso1016 allele. Bioassays of F(3) offspring arising from permethrin susceptible Val1016 homozygous parents and permethrin resistant Iso1016 homozygous parents show that Iso1016 segregates as a recessive allele in conferring kdr. Analysis of segregation between alleles at the 1011 and 1016 codons in the F(3) showed a high rate of recombination even though the two codons are only separated by a ~250 bp intron. The tools and information presented provide a means for early detection and characterization of kdr that is critical to the development of strategies for resistance management.
Abstract.A large-scale phylogenetic study is presented for Cucujoidea (Coleoptera), a diverse superfamily of beetles that historically has been taxonomically difficult. This study is the most comprehensive analysis of cucujoid taxa to date, with DNA sequence data sampled from eight genes (four nuclear, four mitochondrial) for 384 coleopteran taxa, including exemplars of 35 (of 37) families and 289 genera of Cucujoidea. Maximum-likelihood analyses of these data present many significant relationships, some proposed previously and some novel. Tenebrionoidea and Lymexyloidea are recovered together and Cleroidea forms the sister group to this clade. Chrysomeloidea and Curculionoidea are recovered as sister taxa and this clade (Phytophaga) forms the sister group to the core Cucujoidea (Cucujoidea s.n.). The nitidulid series is recovered as the earliest-diverging core cucujoid lineage, although the earliest divergences among core Cucujoidea are only weakly supported. The cerylonid series (CS) is recovered as monophyletic and is supported as a major Cucujiform clade, sister group to the remaining superfamilies of Cucujiformia. Currently recognized taxa that were not recovered as monophyletic include Cucujoidea, Endomychidae, Cerylonidae and Bothrideridae. Biphyllidae and Byturidae were recovered in Cleroidea. The remaining Cucujoidea were recovered in two disparate major clades: one comprising the nitidulid series + erotylid series + Boganiidae and Hobartiidae + cucujid series, and the other comprising the cerylonid series. Propalticidae are recovered within Laemophloeidae. The cerylonid series includes two major clades, the bothriderid group and the coccinellid group. Akalyptoischiidae are recovered as a separate clade from Latridiidae. Eupsilobiinae are recovered as the sister taxon to Coccinellidae. In light of these findings, many formal changes to cucujiform beetle classification are proposed. Biphyllidae and Byturidae are transferred to Cleroidea. The cerylonid series is formally recognized as a new superfamily,
DNA barcoding is a diagnostic method of species identification based on sequencing a short mitochondrial DNA fragment of cytochrome oxidase I (COI), but its ability to correctly diagnose species is limited by the presence of nuclear mitochondrial pseudogenes (numts). Numts can be coamplified with the mitochondrial orthologue when using universal primers, which can lead to incorrect species identification and an overestimation of the number of species. Some researchers have proposed that using more specific primers may help eliminate numt coamplification, but the efficacy of this method has not been thoroughly tested. In this study, we investigate the taxonomic distribution of numts in 11 lineages within the insect order Orthoptera, by analysing cloned COI sequences and further test the effects of primer specificity on eliminating numt coamplification in four lineages. We find that numts are coamplified in all 11 taxa using universal (barcoding) primers, which suggests that numts may be widespread in other taxonomic groups as well. Increased primer specificity is only effective at reducing numt coamplification in some species tested, and only eliminates it in one species tested. Furthermore, we find that a number of numts do not have stop codons or indels, making it difficult to distinguish them from mitochondrial orthologues, thus putting the efficacy of barcoding quality control measures under question. Our findings suggest that numt coamplification is a serious problem for DNA barcoding and more quality control measures should be implemented to identify and eliminate numts prior to using mitochondrial barcodes for species diagnoses.
We present a molecular phylogeny of Nitidulidae based on thirty ingroup taxa representing eight of the ten currently recognized subfamilies. Approximately 10 K base pairs from seven loci (12S, 16S, 18S, 28S, COI, COII and H3) were used for the phylogenetic reconstruction. The phylogeny supports the following main conclusions: (i) Cybocephalidae are formally recognized as a distinct family not closely related to Nitidulidae and its constituent taxa are defined; (ii) Kateretidae are sister to Nitidulidae; (iii) Cryptarchinae are monophyletic and sister to the remaining nitidulid subfamilies; (iv) subfamily Prometopinae stat. res. is reinstated and defined, to accommodate taxa allied to Axyra Erichson, Prometopia Erichson and Megauchenia MacLeay; (v) Amphicrossinae, Carpophilinae and Epuraeinae are shown to be closely related taxa within a well‐supported monophyletic clade; (vi) tribal affinities and respective monophyly within Nitidulinae are poorly resolved by our data and must be more rigorously tested as there was little or no support for prior morphologically based tribes or genus‐level complexes; (vii) Nitidulinae are found to be paraphyletic with respect to Cillaeinae and Meligethinae, suggesting that they should either be subsumed as tribes, or Nitidulinae should be divided into several subfamilies to preserve the status of Cillaeinae and Meligethinae; (viii) Teichostethus Sharp stat. res. is not a synonym of Hebascus Erichson and the former is reinstated as a valid genus. These conclusions and emendations are discussed in detail and presented within a morphological framework.
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