AEDES ALBOPICTUS INVASIONS: HOW AN INVASIVE MOSQUITO VECTOR ADAPTS AND BEHAVES IN NOVEL ENVIRONMENTS.
The mosquito Aedes albopictus is a vector of dengue, chikungunya, and Zika viruses and an extremely successful invasive species. This mosquito exhibits high plasticity and an ability for rapid local adaption, leading to demonstrated variation in behavior among different environments. Therefore, it is critical to understand how its biology varies by ecological context in order for control to be effective. To this end, I completed three studies to better understand Ae. albopictus invasion ecology in populations in New York, USA and Medellín, Colombia. For my final chapter, I applied my understanding of mosquito ecology to the downstream effects on disease, looking at the spatial structure of dengue in Medellín, Colombia. First, I conducted a series of larval surveys for Ae. albopictus across a northern boundary of its United States range in southern New York to test the degree of larval infestation and understand how larval abundance and spatial distribution varied across gradients of impervious surface and household median income. I demonstrated that in one year of our study period, Ae. albopictus abundance was greater in sites with higher impervious surface, and that in both years of our surveys, Ae. albopictus larval spatial distribution was more clustered in higher income sites. Aedes albopictus were more likely to be found in shaded containers with vegetation, but other container characteristics did not consistently predict the presence of this species, highlighting the flexibility of Ae. albopictus’ larval habitat. After studying the ecology of Ae. albopictus larvae in one invasive population, I wondered how adult mosquito attraction drives the occurrence of larvae across the landscape. This is of particular relevance in locations where Ae. albopictus encounters established populations of Ae. aegypti with whom larval competition can occur. To test how oviposition attraction might enhance or decrease larval interspecific competition, I completed a series of mark-release-recapture experiments in the field and semi-field in Medellín, Colombia in a site where Ae. aegypti has been well established and Ae. albopictus has recently invaded. I set out experimental ovitraps with either Ae. aegypti or Ae. albopictus larvae at one of two natural larval densities or, as a control, no larvae. I found that Ae. albopictus were preferentially attracted to containers with larvae over those without, and that the species and density of larvae in the containers modulated that attraction. While completing the larval survey study in New York, I saw that populations continued to be active well into the fall, beyond the predicted onset of overwintering egg diapause in this region. To better understand the timing and environmental cues driving diapause behavior, I tested diapause incidence in the field along Ae. albopictus’ invasive northern US boundary. Our field results showed that rather than the expected rapid, population-wide switch into diapause centered on a critical photoperiod in early August, diapause incidence stayed below 100% through our final collection date and was predicted by temperatures at a two-week lag. We followed up our field experiment with a laboratory test of populations from New York as well as a population from North Carolina one from Florida. We found that the New York populations’ diapause incidence responded robustly to temperature, the North Carolina populations had an inconsistent response to temperature, and the Florida population showed no response to temperature. These findings will enable more accurate models and predictions of Ae. albopictus population growth and expansion. Finally, in a departure from my previous chapters, I tested how the construction of public transit infrastructure has altered the spatial structure of dengue infection in Medellín, Colombia. The public transit system in Medellín has increased between 2008 and 2016. We show that, in that same time period, dengue incidence was higher in zones of the city that were closer to public transit and in zones that have the higher rates of metro usage. The spatial distribution of dengue cases shifted after the construction of each new transit line; zones that became closer to public transit after new lines opened had an increased density of dengue cases. Finally, lower socioeconomic status predicted higher dengue rates in the later years of our study period, after the major expansion of the transit system. We believe this study will help create improved fine-scale risk maps for dengue that can direct focal mosquito control within the space of a city.
Aedes albopictus; Ecology; Invasive species; Medical entomology; Mosquito; Vector biology
Poveda, Katja; McArt, Scott; Murdock, Courtney
Ph. D., Entomology
Doctor of Philosophy
dissertation or thesis