Hennen, Derek Alan2021-10-222021-10-222020-04-29vt_gsexam:25063http://hdl.handle.net/10919/105631Millipedes (class Diplopoda) are ubiquitous in forests worldwide, with about 12,000 described species and an estimated 30,000 undescribed species. The most species-rich order is the Polydesmida, the flat-backed millipedes, which encompasses about 3,500 species. Appalachia has an abundance of Polydesmida, and is a biodiversity hotspot for millipedes in the family Xystodesmidae. These diplopods are chemically defended with hydrogen cyanide and benzaldehyde, and sometimes form mimicry rings based on shared color. The evolutionary dynamics of model and mimic are incompletely known in these rings, so I investigated a mimicry ring in the central Appalachian Mountains to determine if the species Apheloria polychroma functions as a model for the genus Brachoria. I measured the size of the chemical gland to assess toxicity in 15 species, and reconstructed the ancestral dimensions of the gland to determine the direction of volume change over evolutionary time. Using a molecular phylogeny, I traced the miniaturization of chemical glands in the mimic genus Brachoria and found that in areas without Apheloria, Brachoria and related xystodesmids have larger chemical glands. Non-aposematic millipedes of the genus Nannaria have significantly smaller glands, and ostensibly rely on camouflage to avoid predation. This genus is known as the twisted claw millipedes and occur throughout eastern North America, but have their center of diversity in the Appalachian Mountains. About 22 species are described, but many undescribed species are known. To determine the diversity of this group, field collection and examination of museum specimens took place from 2015-2020. Examination of morphology, combined with molecular phylogenetics, revealed two distinct clades in the genus. One is distributed throughout the eastern United States, while the other is found only in the Appalachian Mountains. This Appalachian clade contains six described species, and I describe an additional 18 species, quadrupling the diversity of the group. Additionally, the phylogenetics of the polydesmid genus Pseudopolydesmus is investigated in an integrative taxonomic framework using five genes. I find that the genus is monophyletic, contains 8 species, and are related to one another in a hierarchical way according to a molecular phylogeny. I provide complete distributional records and live photographs of each species.ETDIn CopyrightDiplopodasystematicsintegrative taxonomyPseudopolydesmusNannariachemical ecologyXystodesmidaePolydesmidaeDissertation