Date of Award
Master of Science
The North American Astereae clade (Asteraceae: Astereae) represents an ecologically important lineage whose species frequently comprise early to mid-successional ecosystems primarily throughout the United States. In the eastern U.S., most species are perennial suffrutescent herbs whereas many in the western U.S. are shrubs or subshrubs, particularly in the Solidagininae s.l. The delimitation of this subtribe, however, has remained unclear as molecular phylogenetics have not resolved whether the Solidagininae s.s. and another clade, the Gutierrezia lineage, collectively form the Solidagininae s.l. To evaluate the relationships among and within these lineages, high-throughput sequencing was employed across the North American Astereae. Highthroughput sequencing was also used to clarify relationships of one taxonomically contentious genus within the Gutierrezia lineage, Euthamia. Additional Euthamia specimens were amplified via polymerase chain reactions for sequencing two loci to increase phylogenetic sampling within the genus. Subsequent species delimitations based on molecular phylogenetics and morphological evaluations from literature were used to model species distributions through ecological niche modeling. Niche comparisons via the R package ‘Humboldt’ further assessed whether the most closely related species differed considerably in their environmental niche occupation. These collectively outlined the distributions of all nine Euthamia species and indicated that hypothetical sister taxa have diverged environmentally for both allopatric and sympatric species.
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