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.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/105631 |
| Date | 29 April 2020 |
| Creators | Hennen, Derek Alan |
| Contributors | Entomology, Marek, Paul E., Opell, Brent D., Hopkins, William A., Pfeiffer, Douglas G., Shear, William A. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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