Date of Award
8-1-2026
Degree Name
Master of Science
Department
Plant Biology
First Advisor
Neubig, Kurt
Abstract
Dichanthelium (Hitchcock & Chase) Gould is a genus in the grass family (Poaceae) with a wide range of morphological diversity, exhibiting significant ecological differences. Despite this, its evolutionary relationships are not fully understood. The ambiguity surrounding the boundaries of lineages and the relationships among species has hindered the systematics of the genus. This study aimed to reconstruct the phylogenetic relationships within Dichanthelium, verify the monophyly of species, and evaluate the strength of the inferred relationships across different analytical frameworks. Molecular sequence data of entire plastomes were examined using both maximum likelihood and Bayesian inference methods to develop phylogenetic hypotheses. Phylogenies were constructed using model-based frameworks, with node support evaluated through bootstrap resampling and posterior probability estimation. The consistency between analytical methods was assessed to determine the stability of the inferred topologies. Both maximum likelihood (ML) and bayesian inference (BI) produced highly consistent phylogenetic topologies, differing mainly in node support values rather than branching structure. While the use of a single outgroup constrained Dichanthelium as monophyletic, this analyses consistently resolved several major evolutionary lineages within the genus across different methods. Several species were not monophyletic in these analyses, including Dichanthelium oligosanthes, D. ovale, D. acuminatum, D. aciculare, D. leucothrix, and D. ensifolium. Many relationships were generally well-resolved, although some deeper backbone nodes showed reduced bootstrap support, likely due to the limited phylogenetic signal associated with early diversification events. Overall, this study established a robust and methodologically consistent phylogenetic framework for Dichanthelium. The agreement of model-based inference methods enhances confidence in the inferred relationships and offers a stable foundation for future taxonomic, evolutionary, and ecological studies of the genus.
Access
This thesis is Open Access and may be downloaded by anyone.