Graduate Thesis Or Dissertation
Mollusks, Microbes, and Museums: Characterizing a Land Snail’s Microbiome Across Ontogeny, Time, and Space Public Deposited
Research on biodiversity often concentrates on the impacts of individual species, however, important aspects of biodiversity are the complex biological interactions between species. One example of such an interaction is that between a host and its microbial symbionts. Preserved museum specimens are valuable tools for exploring host/microbe associations. Specimen-associated microbiomes may now be characterized thanks to high-throughput sequencing approaches, providing incredible opportunity to investigate aspects of microbial ecology across wide temporal and geographic gradients. This dissertation used Oreohelix strigosa, a native Coloradan land snail, to investigate how life stages, preservation time, geographic distributions, and environmental factors impact the gut microbiome.
I first reviewed the known symbiotic relationships between microbes and molluscan hosts to gain insight into the types of microbial symbiosis present in this hugely diverse phylum. I then characterized the core gut microbiome of the land snail O. strigosa and its microbiome variation across life stage and starvation status. Comparisons of gut microbiomes in adult, fetal, and starved samples provide evidence that bacteria may be transmitted vertically from parent to offspring, and that stress influences the microbiome. A core microbiome was present across varying life history metrics. To investigate the efficacy in utilizing preserved museum specimens to answer microbial ecology questions, I determined the stability of the gut microbiome in O. strigosa specimens across a 98-year time range. There were consistent patterns in the gut microbiome across this temporal range. Long-term preservation was not the greatest factor in shaping microbiome compositions; geography was a larger factor. Last, I investigated biogeographic patterns of gut microbiomes in populations originating from across O. strigosa’s native geographic range. Geography explains high levels of variation in the gut microbiome. Several small-scale environmental factors may be driving the changes in gut microbiome composition seen across large-scale geography.
Altogether, this dissertation suggests that O. strigosa contains a stable and diverse gut microbiome, which can shift in response to many factors, including life stage, starvation stress, geographic location, and components of its habitat, but is also largely stable across time in preservation. Exploration of microbiome variation is required to form a sound baseline for further experimental study.
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