Análise da variabilidade genética e a influência da temperatura e concentração de CO2 em populações de Aedes aegypti na cidade de Manaus

Abstract

Aedes aegypti is the main vector of dengue, zika, chikungunya and yellow fever viruses in tropical and subtropical regions and is an important public health problem. This species has demonstrated high adaptive capacity in the most diverse conditions, such as the development of resistance to pyrethroids and other insecticides, in response to the high adaptive capacity of these chemical compounds. This resistance is due to mutations at different sites of the sodium channel gene, including Kdr (Knockdown resistance) at site 1016, where the substitution of a Valine by an Isoleucine (Val1016Ile) occurs. It is estimated an increase of 1,4 °C a 5,8 °C in the average global temperature and of 855 to 1300 ppm in the concentration of CO2 in the atmosphere by 2100. These conditions may have influence on the genetic variability of A. aegypti, affecting its adaptive capacity, Also, a great concern as to the influence that these conditions can exert on this mutation. In this work, the genetic variability of four populations of this species in Manaus (Novo Aleixo, Morro da Liberdade, Jorge Teixeira and Lírio do Vale) and two others in simulated conditions of temperature increase and CO2 concentration: Room 03 (+2.5 °C; +400 ppm) and Room 04 (+4.5 °C; +800 ppm) using five RAPD markers and the Val1016Ile mutation of the Kdr gene. The results show that of the four natural populations, for RAPD, that of Jorge Teixeira presented the highest genetic variability (P = 82.00; Ho = 0.3245; He = 0.3297) and the Lírio do Vale, the lowest variability (P = 74.00; Ho = 0.2667; He = 0.2712). Of the populations of the Microcosmos, that of Room 03 showed greater variability (P = 86.00; Ho = 0.3293; He = 0.3336). However, considering all the analyzed populations, the latter, even under the conditions +2.5 °C and +400 ppm of CO2, continued with greater variability. This result is probably because this population originated from the mixture of three different populations and because its adaptive capacity was not affected in these conditions of CO2 temperature and pressure. The genetic structure data of the populations showed genetic differentiation (Fst = 0.1331 ± 0.1072), possibly due to the isolation of the populations of rooms 03 and 04. The greatest genetic similarity observed among the natural populations was between the Morro da Liberdade and Jorge Teixeira (D = 0.0289) and the lowest between Morro da Liberdade and Lírio do Vale (D = 0.0831). For the Kdr gene, the frequency of the 1016Ile mutant allele was lower than that of the wild-type Val1016 allele in all natural populations, ranging from 0.2069 to 0.4118, being completely absent in the Microcosm populations. These results show that the levels of genetic variability of these natural populations analyzed were high, according to other studies previously recorded in other populations of Manaus. The results may be related to factors such as natural selection, genetic drift, inbreeding and chemical control. In the populations of the Microcosmos, the lower variability of Room 04 should be related to extreme conditions of CO2 temperature and pressure, which exceed the limits tolerable by the adaptive capacity of A. aegypti. In relation to the Kdr gene, the mutant allele (1016Ile) presented low frequency in the analyzed natural populations and was absent in the Microcosmos, showing that this allele may be affected by negative sealing of the conditions in the Microcosmos. Keywords: Aedes aegypti, Variabilidade genética, RAPD, Kdr.