INVESTIGATING PATTERNS AND VARIATIONS IN AEDES ALBOPICTUS (DIPTERA: CULICIDAE) AND ITS MICROBIOME IN HAWAII

Abstract

Understanding the drivers of distribution and abundance of invasive species remains a significant challenge especially on the Hawaiian Islands. Mosquitoes (Diptera: Culicidae) are non-native to Hawai’i and the diseases they vector are a contemporary threat to human and wildlife health. Despite being a well-established mosquito species, Aedes albopictus (Skuse) distribution and the factors influencing the population and its host associated microbiome in Hawaiʻi are poorly understood. In this study, I investigate how the environment influences the distribution and abundance of Ae. albopictus and the diversity and distribution of its host-associated microbiome in Hawaiʻi. In a yearlong island-wide surveillance study on Maui, the patterns of mosquito distribution were evaluated in relation to environmental factors (rainfall and temperature), elevation, space, and time using both oviposition and adult traps. Overall, four mosquito species were detected, Ae. albopictus, Ae. vexans, Culex quinquefasciatus, and Wyeomyia mitchellii. The survey determined that Aedes albopictus is abundant and widely distributed around Maui, and adult abundance and oviposition varied with site and time of collection. The oviposition of Ae. albopictus was positively associated with sites that are warm and low elevation, while the abundance of adults was not influenced by the environmental variables. The complex characteristics of each site such as vegetation, land use and host availability likely influenced the abundance of adult Ae albopictus and its ovipositional activity. However, Culex quinquefasciatus, Ae. vexans, and W. mitchellii were not frequently collected, and were not assessed in relation to space, time, or environmental variables. The trapping methods and frequency and intensity of sampling are likely to have been the main drivers behind the probability that these species and others were collected. Nonetheless, these findings can be used provide a baseline for future mosquito surveillance studies to assess new mosquito species incursions, and range expansion. Adult Ae. albopictus collected in the above survey were used to assess host associated microbiome in relation to space, time, rainfall, temperature, and host infection with a co-occurring pathosymbiont Ascogregarina taiwanensis. The microbiome of Ae. albopictus was found to vary across the island and be influenced by infection status with A. taiwanensis. The microbiome of Ae. albopictus did not shift in accordance with gradients of temperature or rainfall, suggesting that mosquitoes actively maintain their microbiome. As with the distribution of the adult mosquitoes, the complex factors associated with various sites, are diving the differences in the host-associated microbiome across geographic location. This study also highlights that inter- and intra-domain interactions may structure the Ae. albopictus microbiome. Cumulatively, understanding the explicit drivers of the mosquito microbiome assembly may have important implications in developing mosquito control strategies. I further explored how the microbiome is heterogeneous within the host and demonstrate that the environment provides the source of microbes. Results indicate that the microbiome of Ae. albopictus tissues is compositionally nested within the environmental microbiome i.e. microbes within the mosquito tissues are also found in the soil, water and on plants in the mosquito habitat. Within the mosquito, the microbiomes of the crop, midgut, Malpighian tubules, and ovaries differed in composition. The microbiomes of mosquitoes tissues formed two specialized modules, one in the crop and midgut and another in the Malpighian tubules and ovaries. The specialized modules may form based on microbe niche preferences and/or selection of mosquito tissues on specific microbes that may aid unique biological functions of the tissue types. Strong niche-driven assembly of tissue-specific microbiotas from the environmental species pool suggests that each tissue has specialized associations with microbes, which perhaps derive from host-mediated microbe selection. Overall, this study investigated the drivers of distribution, and abundance of Ae. albopictus and additionally the diversity, distribution and abundance of the host-associated microbiome present in Hawaii. These findings fill an important gap in understanding about a significant disease vector and provide information for future surveillance and studies, particularly those that lead to the development of novel methods of mosquito management.