Millipedes (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. / Doctor of Philosophy / Millipedes are common animals in forests. There are about 12,000 known species in the world, with an estimated 30,000 undescribed species still awaiting discovery and description. The largest group of millipedes are the flat-backed millipedes, with about 3,500 known species. They are some of the most common millipedes in North America, and many of these species defend themselves with poisons that are harmful to predators, but smell sweet like cherries to humans. Some of these millipedes have bright red or yellow spots against dark colors to warn predators of their toxins, and look similar to other species that live near them. I wanted to know if some of these species are more or less poisonous than others, and measured how large their poison reserves were. I found that one species, called Apheloria polychroma, is more poisonous than similar-looking species called Brachoria, which are less poisonous. If Brachoria doesn't live near Apheloria though, Brachoria is more poisonous. Not all of these millipedes are brightly colored, and a group called Nannaria, or the twisted claw millipedes, are camouflaged with brown colors on the forest floor. These millipedes only live in the eastern United States, especially the Appalachians, and aren't found anywhere else in the world. We know about 20 species of them, but based on specimens stored in scientific collections in museums and through discovery from fieldwork, we knew that more species existed. Each species of twisted-claw millipede only lives in a small area, sometimes only a few miles wide, and could be threatened by habitat loss and other dangers. So, to learn more about them, we need to find them in the forest and describe what they look like and most importantly, giving them a name. I did this by collecting them, illustrating their anatomy, and sequencing their DNA. I found two groups within Nannaria, and focused on the group that only lives in Appalachia. Scientists know 6 of these species, but I found 18 more species and describe them. A related group called Pseudopolydesmus lives throughout North America, and I studied their anatomy and DNA as well, finding 8 species.

The Appalachian Mountains contain some of the highest millipede diversity on the planet, including many endemic and range-restricted species. Millipedes have extremely low dispersal capacity, strict environmental requirements for survival and, in the case of the family Xystodesmidae, are completely blind. Coupled with the complex topology of the Appalachians, xystodesmid millipedes have speciated in the eastern United States to a greater degree than in any other region. Many of the taxonomic relationships within the Xystodesmidae remain to be tested using modern molecular techniques, and numerous species await description. The subtribe Nannariina, for example, contains 3 genera and 19 species, yet evidence suggests the tribe may actually contain over 100 species. Traditional taxonomic work has been hindered by a paucity of researchers in the field, and a necessary reliance on morphological characters for species delimitation. The external male genitalia, known as gonopods, are the structures which have most often been used to define species boundaries. However, in many groups, including the Xystodesmidae, the gonopods are extremely simple, making it difficult to discern whether similarity between gonopods is a result of shared ancestry or morphological convergence. Further complicating matters, somatic characters are often uniform between species, and some obvious phenotypes, such as color pattern and hue, are shared between genera in aposematic mimicry rings. Leading to the formation of mimicry rings between distantly related genera, their bright coloration functions to advertise a cyanide-based defense. Some species have been recorded as having six color patterns, each a member of a different mimicry rings. The factors which drive some taxa to participate in mimicry rings, while others have a myriad of hues and patterns, unmatched by other species, are unknown. Here I investigate the phylogenetic relationships between the tribes and genera of the Xystodesmidae, with the aims of (1) understanding the role of homoplasy within the Xystodesmidae, (2) delineating tribal and generic boundaries within the family, (3) describing species in the genus Nannaria for the purposes of revising the subtribe Nannariina, and (4) investigating mimicry and color variability through a detailed color atlas for North American Xystodesmidae. I found that 95% of the morphological characters traditionally used in xystodesmid taxonomy are homoplasious (HI > 0.5), delineated the Apheloriini, Appalachioria and Sigmoria, described 34 new Nannaria species, and created a color and mimicry dataset of 956 Xystodesmidae for use in future studies of color variability. / PHD / Millipedes are soil dwelling animals that eat leaves, decaying wood and, sometimes, fungi. They are typically found beneath dead leaves in damp forests. The Appalachian Mountains are home to an incredible number and variety of millipede species. This is partly due to the age of the Appalachians, which are around 10 – 20 million years old, its rugged terrain, and the fact that the complexity of the terrain acted as a refuge for many different animals during the last ice age. However, millipede behavior also played a role in their diversification. Most millipedes are relatively slow moving, and many are blind. Millipedes also dry out easily, and therefore need to live in very wet habitats. All of these factors led to populations of millipedes becoming isolated in gullies and on mountains throughout the Appalachians. Over time, these populations became distinct species, many of which are still unknown to the scientific world. One group of millipedes in the family Xystodesmidae, the Nannariina, have only 19 known species; however, evidence suggests that the group may contain over 100 undescribed species. There are several reasons that groups such as the Nannariina have so many undescribed species, there are very few people studying them, they live in hard-to-reach areas, they are not pests, invasive, or have immediate economic importance. However, one of the biggest reasons is that traditional descriptions of millipede species rely on physical characters that often are not informative about relatedness (as an example stating that all green-eyed people are closest relatives). Making matters more complex, many unrelated species in the family Xystodesmidae have the same color. There are even millipede species that have six color patterns in one species. We do not know why some millipede species are a single color and others are very colorful. Here I study the evolutionary relationships between members of the Xystodesmidae, with the aims of (1) investigating anatomical convergence within the Xystodesmidae, (2) defining evolutionary groups within the family, (3) describing species in the genus Nannaria, and (4) investigating mimicry and color variability through a detailed color atlas for North American Xystodesmidae.