Estimativas de Variação Genética do Gene ND4 do DNA Mitocondrial em Aedes aegypti (Diptera: Culicidae) da Amazônia, Brasil

Abstract

Aedes (Stegomyia) aegypti (Linnaeus, 1762) is a mosquito of great epidemiological importance as the main vector of urban yellow fever and the four serotypes of the dengue virus. Today, this species is present in all States of Brazil. It has been established that genetics studies of Ae. aegypti population can contribute to the implementation of control strategies. However, in the Brazilian Amazon region little is known about the genetic variability of this mosquito. The aim of this study was to detect genetic variation in a region of the NADH dehydrogenase subunit 4 mitochocondrial gene (ND4) in natural populations of Ae. aegypti in the Brazilian Amazon. Ten populations were studied: four from different districts of the city of Manaus, and one each from the cities of Coari (Amazonas), Santarém and Belém (Pará), Boa Vista and Pacaraima (Roraima), and Rio Branco (Acre). We analyzed 380 base pairs from 123 individuals and found 13 haplotypes, of which 9 were considered unique. The levels of genetic diversity were high in nearly all populations, with the highest values from Belém (h = 0.782; = 0.0170) and the districts of Coroado (h = 0.737; = 0.0136) and Praça 14 de Janeiro (h = 0.745; = 0.0155) in Manaus. The tests of neutrality Tajima s D and Fu s Fs were not significant (P > 0.05) for all samples, indicating that the genetic polymorphism is in agreement with the neutral model of mutations. The results of the first AMOVA showed that the greater part of the variation occurred within populations (72.69 %; FST = 0.273; P < 10-5). The second AMOVA, grouping populations according to State, also indicated that most variation was within the population (70.66%; FST = 0.293; P < 10-5). The FST values for most of the comparisons between the 10 populations were not significant, indicating the existence of gene flow between them. Intense gene flow was observed among pairs of geographically distant populations such as Santarém and Boa Vista (Nm = 35.1) and Tancredo Neves (Manaus) and Belém (Nm = 9.3). The population of Pacaraima and Rio Branco were well structured in comparison with the other populations, indicating restricted gene flow in relation to the most common haplotypes (H1 and H6). Correlation between genetic and geographic distances among the ten populations was significant (r = 0.5815; P = 0.006). However, except for Rio Branco and Pacaraima, the Mantel test was not significant, indicating that genetic distance was not related to geographical distance. The dendrograms of haplotypes and populations show two groupings indicating distinct lineages. These result, together with the observed levels of genetic variability and comparison with haplotypes found in other studies, suggest that Ae. aegypti may have been introduced into Amazonia at least twice: once into Boa Vista, originating from Mexico and Venezuela; e once to Belém from the rest of the country or across the Atlantic.