Date of Award

2021

Document Type

Honors Thesis (Open Access)

Department

Colby College. Biology Dept.

Advisor(s)

David Angelini

Second Advisor

Suegene Noh

Third Advisor

Christopher Moore

Abstract

The microbiome is increasingly recognized for its complex relationship with host fitness. Akin to primates and other social animals, bumblebees harbor a specific microbiome derived from social contact. The bumblebee microbiome is characteristically species poor, with just a few “core” phylotypes accounting for the majority of total abundance. Genomic analyses reveal phylogenetic congruence and adaptation of the core endosymbionts to the bumblebee gut, indicating a shared evolutionary history. Prior investigations reveal that the relative abundance of core microbes is negatively associated with infection by a trypanosome, Crithidia bombi, and that the microbiome has a mechanistic role in immunity. As an extension of these studies, we have deeply sampled wild bumblebee populations throughout central and down east Maine in a three-year microbiome field survey. The wild bees of the field survey consistently host high abundances of the previously recognized core microbes, as well as low abundant, environmentally derived taxa. Community composition appears to be dependent on colony lifecycle but is largely robust to the horizontal exchange of microbes, supporting the narrative of a robust and coevolved bumblebee microbiome. Compositional variation additionally shows a relationship with Crithidia bombi infection severity. Bumblebees with high relative abundances of core microbes have lower infection loads. The relative abundances of two core phylotypes, Lactobacillus and Apibacter, are particularly strong indicators of host health. However, as relative abundance does not directly reflect absolute abundance, total community composition may be a better indicator of health than the relative abundance of single taxa.

Keywords

Microbiome, Dysbiosis, Bumblebee, Crithidia, Symbiosis, Metagenomics

Available for download on Saturday, June 11, 2022

Click below to download supplemental content.

Analysis_Final.zip (15243 kB)
All data and analysis files.

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