Taxonomic and phylogenetic relationships between species of the genus Culex (Diptera: culicidae) from Brazil inferred from the cytochrome c oxidase I mitochondrial gene.

Species of the genus Culex Linnaeus have been incriminated as the main vectors of lymphatic filariases and are important vectors of arboviruses, including West Nile virus. Sequences corresponding to a fragment of 478 bp of the cytochrome c oxidase subunit I gene, which includes part of the barcode region, of 37 individuals of 17 species of genus Culex were generated to establish relationships among five subgenera, Culex, Phenacomyia, Melanoconion, Microculex, and Carrollia, and one species of the genus Lutzia that occurs in Brazil. Bayesian methods were employed for the phylogenetic analyses. Results of sequence comparisons showed that individuals identified as Culex dolosus, Culex mollis, and Culex imitator possess high intraspecific divergence (3.1, 2.3, and 3.5%, respectively) when using the Kimura two parameters model. These differences were associated either with distinct morphological characteristics of the male genitalia or larval and pupal stages, suggesting that these may represent species complexes. The Bayesian topology suggested that the genus and subgenus Culex are paraphyletic relative to Lutzia and Phenacomyia, respectively. The cytochrome c oxidase subunit I sequences may be a useful tool to both estimate phylogenetic relationships and identify morphologically similar species of the genus Culex.

Intragenomic variation in the second internal transcribed spacer of the ribosomal DNA of species of the genera Culex and Lutzia (Diptera: Culicidae).

Culex is the largest genus of Culicini and includes vectors of several arboviruses and filarial worms. Many species of Culex are morphologically similar, which makes their identification difficult, particularly when using female specimens. To aid evolutionary studies and species distinction, molecular techniques are often used. Sequences of the second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) from 16 species of the genus Culex and one of Lutzia were used to assess their genomic variability and to verify their applicability in the phylogenetic analysis of the group. The distance matrix (uncorrected p-distance) that was obtained revealed intragenomic and intraspecific variation. Because of the intragenomic variability, we selected ITS2 copies for use in distance analyses based on their secondary structures. Neighbour-joining topology was obtained with an uncorrected p-distance. Despite the heterogeneity observed, individuals of the same species were grouped together and correlated with the current, morphology-based classification, thereby showing that ITS2 is an appropriate marker to be used in the taxonomy of Culex.

Intragenomic variation in the second internal transcribed spacer of the ribosomal DNA of species of the genera Culex and Lutzia (Diptera: Culicidae)

Culex is the largest genus of Culicini and includes vectors of several arboviruses and filarial worms. Many species of Culex are morphologically similar, which makes their identification difficult, particularly when using female specimens. To aid evolutionary studies and species distinction, molecular techniques are often used. Sequences of the second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) from 16 species of the genus Culex and one of Lutzia were used to assess their genomic variability and to verify their applicability in the phylogenetic analysis of the group. The distance matrix (uncorrected p-distance) that was obtained revealed intragenomic and intraspecific variation. Because of the intragenomic variability, we selected ITS2 copies for use in distance analyses based on their secondary structures. Neighbour-joining topology was obtained with an uncorrected p-distance. Despite the heterogeneity observed, individuals of the same species were grouped together and correlated with the current, morphology-based classification, thereby showing that ITS2 is an appropriate marker to be used in the taxonomy of Culex.

Caracterização do segundo espaçador interno transcrito do DNA ribossômico de espécies do gênero Culex e Lutzia bigoti (Diptera, Culicidae) / Characterization of the second internal transcribed spacer ribosomal DNA of species of the genus Culex and Lutzia bigoti (Diptera, Culicidae)

Culex é o maior gênero da tribo Culicini, com 767 espécies descritas e inclui vetores de muitos arbovírus e filárias. Apesar disso, estudos sobre sua taxonomia e filogenia ainda são muito escassos. A identificação dos mosquitos, etapa fundamental para estudos epidemiológicos, ecológicos e genéticos, geralmente é feita com base nos caracteres morfológicos. Entretanto, muitas espécies de Culex são morfologicamente semelhantes, dificultando a identificação correta. Atualmente, técnicas moleculares são utilizadas em estudos de evolução e na distinção de espécies. Dessa forma, seqüências de ITS2 do DNAr de 15 espécies de gênero Culex e uma do gênero Lutzia foram clonadas e seqüenciadas, para examinar o nível de divergência genômica e verificar aplicabilidade desse marcador em análises filogenéticas no grupo estudado. Três a sete clones por indivíduo foram seqüenciados, gerando 144 seqüências com comprimentos de 199 a 339 pb. Foi gerada topologia de distância pelo método de Neighbour-joining (NJ), com p-distance não corrigido. A matriz de distância gerada evidenciou a presença de variação intragenômica e intra-específica. Dos 31 espécimes clonados e seqüenciados, apenas um de Culex (Culex) mollis apresentou todas suas seqüências idênticas (5 clones), enquanto um exemplar de Culex (Cux.) coranator apresentou diferença na composição nucleotídica entre todos os seus clones (6 clones). Devido à presença de variabilidade intragenômica, optou-se por selecionar as cópias que seriam utilizadas nas análises de distância empregando a similaridade das estruturas secundárias do ITS2. Assim, foi possível eliminar as cópias mais divergentes e que apresentavam similaridade inferior a 75 por cento. Apesar da heterogeneidade observada, as seqüências geradas de indivíduos das mesmas espécies se agrupam e foi condizente com a atual classificação baseada em morfologia. A topologia de NJ indica a possível monofilia dos subgêneros Melanoconion e Microculex. No entanto, indica também o p...