Microclimate and Larval Habitat Density Predict Adult Aedes albopictus Abundance in Urban Areas

The Asian tiger mosquito, Aedes albopictus, is an invasive mosquito that became established in the United States following its introduction in 1985.1,2 Aedes albopictus can transmit several pathogens of public health importance, including La Crosse,3 dengue,4,5 and chikungunya viruses.6 Unlike another vector of these diseases, Aedes aegypti, which originated in east Africa, Ae. albopictus originated from a temperate area of Asia and is able to survive in cooler climates than Ae. aegypti. Following initial establishment in Texas, Ae. albopictus has invaded more than 40 states,7 and models predict its range will expand as the climate warms.8,9 At present, established populations of Ae. albopictus are found in the United States as far north as Connecticut and New York,10,11 well outside the present range of Ae. aegypti. Aedes albopictus is implicated in transmission cycles of dengue and chikungunya in the Mediterranean region of Europe,12,13 which suggests that temperate regions of the United States may be similarly vulnerable. Given the potential role of Ae. albopictus in disease transmission, it is important to understand what factors influence its abundance. Ae. albopictus is sensitive to variation in temperature because of temperature-dependent life history traits, such as development rates, fecundity, and survival.14–16 Climate or meteorological predictors are widely used in mechanistic models and statistical models.17–22 Models leverage these relationships to predict mosquito presence, population growth rates, and abundances based on temperature metrics derived from weather stations or remotely sensed datasets. However, urban landscapes are composed of a variety of land classes (e.g., residential, developed, and vegetated), which vary in their microclimates at fine spatial scales less than 1 × 1 km.23–25 This difference in microclimate can alter mosquito population growth rates,26,27 leading to variation in population abundances that may be missed by models that rely on coarser spatial data. In addition, adult abundance may be determined by the abundance of larval habitat. Ae. albopictus is fairly nondiscriminate in its habitat use, and larvae are found in both natural and artificial containers.11,28,29 Several studies have found that adult abundance is positively related to the availability of larval habitats.30,31 This relationship is also the basis for larval source reduction techniques widely used in vector control.32 Urban microclimates can covary with the mosquito larval habitat density, which may differ in quality and quantity across urban land use.26,30 Thus, when studied independently, the relative roles of microclimate and larval habitat may be confounded. Here, we combine field surveys of larval habitat and adult mosquito abundances with microclimate data to investigate how microclimate and the availability of larval habitat contribute to changes in adult Ae. albopictus abundance across an urban landscape. We aim to answer the following questions: 1. Does the density of larval habitat positive for Ae. albopictus change across urban land classes? 2. Does the abundance of Ae. albopictus adults change across urban land classes? 3. What is the relationship between microclimate and adult abundance? 4. What is the relationship between larval habitat and adult abundance? By investigating these relationships, our results inform if and how predictive models should include microclimate variables and data on larval habitat from the field in their predictions of adult Ae. albopictus abundance. Furthermore, these results can help determine whether variation in land class alters the spatial distribution of Ae. albopictus and whether omitting this fine-scale variation may lead to bias in models.