Author ORCID Identifier

https://orcid.org/0000-0001-5841-0481

Semester

Spring

Date of Graduation

2025

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Craig Barrett

Committee Co-Chair

Stephen DiFazio

Committee Member

Stephen DiFazio

Committee Member

Jennifer Hawkins

Committee Member

Donna Ford-Werntz

Committee Member

Cynthia Huebner

Abstract

Zinniinae is a subtribe of plants in the daisy family (Asteraceae) and the sunflower tribe (Heliantheae). Traditionally, seven genera were included in the subtribe: Echinacea, Heliopsis, Philactis, Sanvitalia, Tehuana, Trichocoryne, and Zinnia. The subtribe is poorly understood from a phylogenetic and taxonomic standpoint, and I undertook a phylogenetic investigation of Zinniinae, using both the plastid genome (plastomes) and the nuclear genome, to learn more about the evolutionary history of this clade. Plastomes were assembled to build a phylogenetic tree, targeted sequence capture was used to compile the nuclear datasets, and a chronogram was created to estimate date ranges for major splits in Zinniinae. In chapter two, I showed that the inclusion of introns, spacers, and indels can improve node support in phylogenetic trees. The five genera of the sister subtribe Spilanthinae (Acmella, Oxycarpha, Salmea, Spilanthes, and Tetranthus) were placed into Zinniinae to preserve monophyly due to the anomalous placement of Heliopsis longipes, H. novogaliciana, and Trichocoryne connata. In chapter three, I uncovered cytonuclear discordance, the effects of paralogs on tree building, and further paraphyly in Heliopsis. Fifteen nodes deviated from the expected patterns of incomplete lineage sorting, and ancient introgression/hybridization was detected between Heliopsis and Zinnia. In chapter four, I investigated the biogeography of Zinniinae as it diversified across Mexico during climatic shifts from the Eocene through the Oligocene into the Miocene. Together, this dissertation resulted in the submission of full plastomes and nuclear datasets new to science to publicly available repositories, new taxonomic combinations, and the first detailed chronogram for the clade.

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