Distribution of mosquitoes within the varzea of the Amazon River

With the objective of using the distribution of mosquito species as an indicator of geographical differentiation of environments within the floodplain (varzea) of the Amazon River in Brazil, we used CDC traps to make 367 nocturnal collections of adult mosquitoes at 50 sites distributed inside lowland coastal floodplain forest along the Amazon river between Tabatinga and Ajurixi, from September to November 2003, resulting in the capture of over 135,000 mosquitoes. Due to the high volume of specimens, we made a subsample of the collected material, which included specimens from 74 collections distributed in 25 localities, for a total sampling effort of 888 trap hours, resulting in a total of 16,123 mosquitoes from nine genera representing 58 different taxa. The genus Uranotaenia presented the highest number of species (26%) and the second largest number of individuals (20%) followed by Culex with 24% of the species and the largest number of individuals (45%). The genus Anopheles had the third highest number of species (9 species) in spite of accounting for less than 4% of the captured specimens. The most abundant species was Culex ocossa followed by Coquillettidia venezuelensis, Uranotaenia ditaenionata, Mansonia amazonensis and Aedeomyia squamipennis. The diversity of mosquitoes per location ranged from 9 to 28 species. However, there was no significant difference in the number of species collected between the floodplain zones. Likewise, there was no significant correlation between the number of species and the longitude along the Amazon River. The mosquito species community changes gradually along the river, both in the pattern of species replacement as in the relative abundance of each species, with some species showing a uniform distribution. These results represent the largest standardized mosquito inventory of the Amazonian lowland floodplain forest ever done with the identification of 58 taxa distributed in 25 different localities.