Microgeographic population structuring of Aedes aegypti (Diptera: Culicidae)

Abstract

Aedes aegypti is one of the species most favored by changes in the environment caused by urbanization. Its abundance increases rapidly in the face of such changes, increasing the risk of disease transmission. Previous studies have shown that mosquito species that have adapted to anthropogenic environmental changes benefit from urbanization and undergo population expansion. In light of this, we used microsatellite markers to explore how urbanization processes may be modulating Ae. aegypti populations collected from three areas with different levels of urbanization in the city of São Paulo, Brazil. Specimens were collected at eleven sites in three areas with different degrees of urbanization in the city of São Paulo: conserved, intermediate and urbanized. Ten microsatellite loci were used to characterize the populations from these areas genetically. Our findings suggest that as urbanized areas grow and the human population density in these areas increases, Ae. aegypti populations undergo a major population expansion, which can probably be attributed to the species’ adaptability to anthropogenic environmental changes. Our findings reveal a robust association between, on the one hand, urbanization processes and densification of the human population and, on the other, Ae. aegypti population structure patterns and population expansion. This indicates that this species benefits from anthropogenic effects, which are intensified by migration of the human population from rural to urban areas, increasing the risk of epidemics and disease transmission to an ever-increasing number of people.

Fine-Scale Population Genetic Structure of Dengue Mosquito Vector, Aedes aegypti and its Association to Local Dengue Incidence

“…aegypti that consisted of a micro-geographic or fine-scale study area. In Sao Paulo, Brazil, for example, the level of genetic differentiation ranged from 0.002 to 0.094 with a maximum distance among collection sites of 30 km [14]. Cities in Southeast Asian countries also showed low levels of genetic differentiation from 0.026 - 0.032 with a spatial scale of 5 - 50 km [11].…”

“…Despite the many population genetic studies of Ae. aegypti using microsatellites worldwide, only a handful of studies have investigated the vector’s genetic structure in a fine-scale area [7,11,12,13,14,15,16]. These fine-scale studies are defined as having sampling points within city boundaries, or villages with geographic distances of less than 50 km.…”

“…For instance, spatial genetic differentiation across Ae. aegypti populations was evident in spatial scales within city boundaries [7,11,12,16], among villages [13,14] and along a street [15]. It has been claimed that genetic divergence in small spatial scales is common in Southeast Asia [11] and could also be attributed to the type of breeding sites [15].…”

“…It has been claimed that genetic divergence in small spatial scales is common in Southeast Asia [11] and could also be attributed to the type of breeding sites [15]. Furthermore, multiple inferred clusters of genetic mosquito populations (K= 3–9) were also detected within these fine-scale areas [11,14,16]. It was suggested that a single house or groups of closely situated houses may act as assembling units in forming these genetic clusters [11].…”

“…Early fine-scale population genetic studies of Ae. aegypti [7,8,11,15] had only demonstrated the degree or magnitude of genetic structuring while recent studies [12,16] concentrated on hypothesis testing such as the role urbanization in genetic divergence [14]. Although the results provided relative insights to our understanding of the mosquito vector, it lacks in demonstrating the clustering or distribution of genetically-similar mosquito populations which can reveal notable patterns for it application in vector control.…”