? PROJECT 2: JI, Matthew Medeiros The symbiotic microbiota of mosquitoes has pervasive effects on host traits, including those of vectors of important human diseases like dengue virus, chikungunya virus, and Zika virus. Coordinated interactions between mosquitoes and their microbiota shape mosquito metabolism, development, fecundity, survival, and immune systems. These effects on individual vectors may scale to influence the transmission of infectious human pathogens at the population and community levels. While the mosquito microbiota is known to modulate the capacity of vectors to sustain human pathogen transmission, the factors that contribute to variation in the composition and density of the mosquito microbiota across individual vectors and vector populations remain poorly resolved. The central hypothesis of this proposal posits that (i) environmental, ecological, and genetic forces drive the assembly of the mosquito microbiota; (ii) differences in these forces over time and space produce variation in the microbiota between individual vectors; and, (iii) this variation between individual vectors scales to impact disease transmission among hosts, including humans. To test this hypothesis, this study will employ numerous carefully designed experiments in both field and controlled laboratory settings. These experiments aim to clarify the role of environmental, ecological, and genetic factors in shaping mosquito microbiota diversity using Hawaiian populations of two medically important vectors, Culex quinquefasciatus and Aedes albopictus. In addition, it will investigate the consequences of this diversity on dengue transmission, the most relevant mosquito-borne pathogen in Hawai`i. Expected outcomes of this work include a better model for the assembly of the mosquito microbiota and its cumulative impact on pathogen transmission. Ultimately, this study is expected to have a positive translational impact by informing the development of novel, microbe-based strategies to mitigate mosquito-borne diseases of public health concern.