Genetic Variability and Evidence of Two Distinct Lineages of Aedes aegypti (Diptera, Culicidae) on São Luís Island in Maranhão, Brazil

Aedes aegypti is the principal vector of the yellow fever virus and the four dengue serotypes and its hemorrhag- ic fever viruses. The genetic variability and differentiation of four Aedes aegypti populations from Sao Luis Island in the Brazilian state of Maranhao was analyzed based on the sequences of a fragment of the mitochondrial ND4 gene. A total of 58 sequences of 337 bps were analyzed, revealing the existence of 10 haplotypes, of which five were considered to be unique. Haplotype diversity for the total population was 0.6273 and nucleotide diversity 0.00748. The haplotype tree pro- duced from the data indicated the presence of two mitochondrial lineages of the dengue vector, one of which was charac- terized by the H6 haplotype, found only in the population from one site (Raposa), and may represent the recent introduc- tion of this lineage to the island. The results of the AMOVA indicated that the majority of the genetic variation (74.38%) was found within populations. However, the significant Fst value of 0.2572 indicates a certain inter-population differen- tiation which may result in differences in the vectorial capacity of the insect, its susceptibility to the virus or even re- sistance to insecticides or other ecological adaptations, all of which may limit the effectiveness of programs for the control of Ae. aegypti.