Mosquito-microbe interactions have major roles in mediating mosquito life histories and the capacity of mosquitoes to transmit pathogens to humans. While essential to better understanding mosquito life histories, our knowledge of how microbes influence oviposition behavior and development remains limited, especially in complex polymicrobial communities. This dissertation tested the relationship between aquatic microbial communities and mosquito oviposition behavior. Field studies were conducted in Michigan to investigate how different leaf-litter derived microbial communities (and modifications of the microbes present in those communities) effected mosquito oviposition and survivorship. Additionally, field (Ouidah, Benin) and laboratory assays were used to determine the effect of a bacterial toxin (mycolactone, produced by Mycobacterium ulcerans) on other aquatic microbes and the downstream impacts of those interactions on mosquito oviposition. Ae. japonicus japonicus (Theobald) mosquitoes preferred red oak (Quercus rubra) leaf-derived leachates over other leaf species tested (sycamore Platanus occidentalis, and honeysuckle Lonicera maackii). Leachates displayed distinct bacterial and fungal communities with sterilization of these communities causing a reduction in oviposition. Larval mosquito growth and survivorship were influenced by both leaf type and leachate concentration. The addition of mycolactone, hypothesized to inhibit microbial quorum sensing, to environmental water samples altered bacterial community composition and reduced Aedes egg laying. In addition to reducing oviposition of Aedes aegypti (L.) in a dose-dependent manner, mycolactone up- and down-regulated expression levels of multiple taxa (N = 13) and functional groups (N = 13), suggesting the toxin plays an important role in interactions between M. ulcerans, other environmental microbes, and mosquito behavior. These studies highlight the essential role mosquito-microbe interactions play in oviposition behavior and life history and expand our knowledge of the microbial underpinnings of mosquito oviposition behavior. Additionally, experiments testing the relationship between the microbiota of aquatic macroinvertebrates and environmental conditions were conducted in Ostana, Italy using high-throughput amplicon sequencing. While both environmental conditions and macroinvertebrate species influenced the internal microbiome, species had a larger effect than environmental conditions, suggesting that physiological conditions in macroinvertebrate guts plays a role in what microbes are able to colonize and survive.
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