Author ORCID Identifier

https://orcid.org/0000-0002-2975-686X

Semester

Summer

Date of Graduation

2025

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Not Listed

Committee Chair

Matt Kasson

Committee Member

Brian Lovett

Committee Member

Ember Morrissey

Committee Member

Dan Panaccione

Abstract

Arthropods, or phylum Arthropoda, are the largest group of animals, accounting for over three quarters of all animal records on NCBI Taxonomy. And yet, only 40% of all deposited sequences on NCBI Nucleotide come from arthropods. Clearly, arthropods are an understudied group of animals: they are small, often drab, and lead lives very alien to our own. Arthropods have chitinous exoskeletons, segmented bodies, and jointed appendages, and include crabs, barnacles, insects, spiders, and millipedes. Since the era of DNA based studies took off in the 1980s, DNA and other small molecules have been integral to our understanding of the Earth and the organisms we share it with. Knowledge of evolutionary histories is driven by the number and quality of features examined, and using DNA or other molecular tools provides exponentially more information than even hundreds of physical traits. This knowledge has improved our understading of both cicadas and millipedes, the two arthropods discussed in this dissertation, but there is still much to learn about the even more neglected microbes that form relationships with them. Fungi, or mushrooms, are familiar to most people, but there is far more diversity in this kingdom of life than meets the eye. Not all fungi are saprotrophic, however: many interact with other living things as parasites, pathogens, or mutualists. In this dissertation, we examine the relationships between cicadas and their fungal pathogen Massospora, and the relationships between Colobognath millipedes and their broader community of fungal associates. In Chapter 1, we review the literature on fungi and their symbioses, and introduce cicadas, Massospora, and the Colobognatha. In Chapter 2, we examine the relationships among Massospora species, finding that of the 5 we could find, two of them were actually the same organism. We also provide detailed measurements of many features for these fungi, several of them for the first time. In Chapter 3, we explore the mycobiome of the Colobognath millipede Brachycybe lecontii, providing one of the first mycobiomes for all millipedes. This species alone associates with at least 620 genera of fungi in 9 phyla, and may have symbiotic relationships with a few of them. Their fungal diversity is only eclipsed by the diversity found in Chapter 4, where we sampled fungi from over twenty species of Colobognath millipedes from the United States. Among these millipedes, we recovered over 800 genera of fungi, and here too, we found possible evidence for fungal symbioses. These remarkable discoveries will fuel further studies that may lead to medically important chemical compounds, or even compounds that can be used to repel pests and manipulate pest behaviors. In addition, this work can fuel further studies of these organisms in their own right, which is critically important in a changing world.

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