Theses and Dissertations

ORCID

https://orcid.org/0009-0006-2451-7196

Advisor

Folk, Ryan

Committee Member

Dapper, Amy

Committee Member

Ervin, Gary

Committee Member

Mlsna, Todd

Date of Degree

5-15-2026

Original embargo terms

Immediate Worldwide Access

Document Type

Dissertation - Open Access

Major

Biological Sciences

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Arts and Sciences

Department

Department of Biological Sciences

Abstract

Symphyotrichum, a plant genus traditionally treated within the genus Aster L., comprises >100 species of annual or perennial plants in the Compositae family Asteraceae. One of the most diverse genera in the southeastern US flora, the genus extends across the Americas, the Caribbean as well as eastern Eurasia. Despite its presence across the major American biomes and with distinctive floristic characteristics, several question regarding Symphyotrichum remains obscure. This research project focuses on exploring diverse aspects of Symphyotrichum systematics, biogeography and evolution. I tested three main hypotheses: (1a) Symphyotrichum originated ancestrally across Mexico and eastern North America in the Miocene (>5 mya), followed by vicariance and local radiation, (1b) Biogeographic movement between Mexico and eastern North America ceased by the late Miocene (~5-10 mya) due to the onset of aridification in the interior of North America around the same time, (2) Morphological variability in sympatric Symphyotrichum is shaped primarily by habitat rather than phylogeny, resulting in repeated evolution of multiple plant habits adapted to major biomes of North America, and (3) floral scent has rapidly evolved among species and populations of Symphyotrichum as a major attractant for different pollinators in sympatry. As a unifying framework for testing these hypotheses, I built a robust estimate of phylogeny and species delimitation within Symphyotrichum. Phylogenomic data and biogeographic regionalization were used to study the historical biogeography of this genus with the aim of elucidating the relationship of temperate eastern North American and Mexican floras. Then lower evolutionary levels in the genus were focused, investigating species delimitation in Symphyotrichum using the morphometric, phylogenomic and biogeographic analyses. Finally, pollinator observations, floral volatile chemical characterization, and morphometric data analysis were performed to understand the major drivers of pollination biology in this genus.

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