Phylogenetic study of the order Polydesmida (Myriapoda: Diplopoda)
| dc.contributor.author | Vasquez Valverde, Luisa Fernanda | en |
| dc.contributor.committeechair | Marek, Paul | en |
| dc.contributor.committeemember | Yang, Chin-Cheng Scotty | en |
| dc.contributor.committeemember | Shear, William A. | en |
| dc.contributor.committeemember | Auguste, Albert Jonathan | en |
| dc.contributor.committeemember | Andrews, Robin M. | en |
| dc.contributor.department | Entomology | en |
| dc.date.accessioned | 2025-01-08T09:00:20Z | en |
| dc.date.available | 2025-01-08T09:00:20Z | en |
| dc.date.issued | 2025-01-07 | en |
| dc.description.abstract | Academic abstract The millipede order Polydesmida, or flat-backed millipedes, is the most species rich among the class Diplopoda. At present, the order does not have a phylogenetic systematic classification, and the relationships of the 29 families are unknown. Whole genome DNA sequencing technologies and bioinformatic tools for the analysis of systematic data have improved over the last couple of decades, and have facilitated analysis of phylogenetic relationships. Here I sequenced the whole genomes of 82 species of the order Polydesmida and assembled a set of 281 orthologous genes using aTRAM. These genes were then used to estimate a maximum likelihood phylogeny. The families Paradoxosomatidae, Sphaeriodesmidae, Rhachodesmdidae, Platyrhacidae, Xystodesmidae, Polydesmidae, and Dalodesmidae were recovered as monophyletic groups. Some other families such as Trichopolydesmidae, Chelodesmidae and Macrosternodesmidae now appear to be polyphyletic groups, and a more comprehensive study of their molecular and morphological characters is needed. Phylogenetic trees can be used as maps to trace the evolution of characters in a group. Using the estimated tree for Polydesmida, I mapped morphological and molecular characters to understand their evolution. Traditional taxonomy in millipedes primarily used the morphology of the male gonopods to differentiate species. In my phylogeny, the morphological characters associated with the gonopod were less variable between specimens of the same family than non-gonopodal morphological characters, which showed a great diversity between individuals of the same family. A set of molecular characters that I studied were the gene order of the mitochondrion, as they may be a source of important evolutionary information. I found an inversion of half of the mitochondrial genome, which was consistent for the entire order Polydesmida. The majority of the changes in gene order were observed in the tRNA's, some of which can be considered synapomorphies for some families. Finally, I described three new species of millipedes in the superfamily Platyrhacoidea from southwestern Colombia: Aphelidesmus carcharodus and Pycnotropis svanae in the family Aphelidesmidae, and Barydesmus peineta in the family Platyrhacidae. I present diagnoses, descriptions, color habitus photographs and illustrations for these new species which contribute to the knowledge of millipedes of Colombia. | en |
| dc.description.abstractgeneral | Millipedes are a diverse group of soil dwelling animals that fulfill an important ecological role as decomposers. The Polydesmida, commonly known as flat-backed millipedes, is the millipede order with the greatest number of described species. Despite its richness, the evolutionary relationships of the families of the Polydesmida are not currently known. I extracted and sequenced DNA from the genomes of 82 polydesmidan species to construct an evolutionary tree. My results showed that many families, such as Paradoxosomatidae, are well defined groups. The evolutionary tree was then used as a map to determine how some morphological characters have evolved in the group through time. Traditionally in the study of millipede classification, the male sexual organs or gonopods are used to differentiate species. Here I found that the gonopod morphology is more useful to understand the relationships between families than other morphological characters as the shape of the body that is greatly variable and do not show consistent evolutionary patterns. I found that the genetic information encoded by the mitochondria of millipedes is useful to understand their evolution. Mitochondria have a single chromosome with genes that change in position during evolution, and those changes are consistent amongst individuals of the same family. Lastly, I described three new species of polydesmidan millipedes from the Private Nature Reserve "Finca Merenberg" in the southwestern of Colombia, and I named these new species: Aphelidesmus carcharodus, Pycnotropis svanae, and Barydesmus peineta. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:42270 | en |
| dc.identifier.uri | https://hdl.handle.net/10919/123916 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Polydesmida | en |
| dc.subject | phylogenomic | en |
| dc.subject | mitochondrial genome | en |
| dc.subject | taxonomy | en |
| dc.title | Phylogenetic study of the order Polydesmida (Myriapoda: Diplopoda) | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Entomology | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
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