EVOLUTION AND BIOGEOGRAPHY OF THE GENUS TRIODANIS

Author

Taylor Simmonds, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2025

Degree Name

Doctor of Philosophy

Department

Plant Biology

First Advisor

Weber, Jenn

Abstract

Campanulaceae Juss., the bellflower family, is a generally well-collected cosmopolitan group of flowering plants, offering a wealth of herbarium information. This family comprises approximately 84 genera and 2400 species within five major subfamilies. Found on six continents in diverse habitats, the group exhibits incredible morphological variation, even within populations. Several studies have made significant progress toward a robust phylogeny for Campanulaceae; however, many species-level relationships remain unresolved. Further research employing genomic methods, such as next-generation sequencing, is the logical next step in bringing phylogenetic clarity to the groups. Resolving species-level taxonomic relationships within Campanulaceae would allow for a more complete understanding of evolution within the family by adding much needed evolutionary context to ecological and life history questions.Together, widespread hybridization and phenotypic plasticity may convolute and impede attempts at bringing taxonomic clarity as well as complicate identification based strictly on morphology. This is evident in the focal study system throughout this dissertation, Triodanis, a small genus of annual bellflowers native to North- and South America. A phylogenetic perspective of this group would allow us to explore ecological, biogeographical, and phenological processes which, in turn, provide the foundation for a deeper understanding of biological processes such as predicting adaptability and habitat suitability, population dynamics, and reproductive success. Understanding drivers of population dynamics and connectivity, especially in the context of the dynamic nature of intrinsic (e.g., reproductive system, hybridization) and extrinsic factors (e.g., physical barriers to gene flow) across space and time, is central to understanding phylogeography and biogeography. These interactions generate complex biological processes that influence contemporary patterns of genetic diversity. In this context, plants offer a unique system to study these topics as herbarium records offer vast amounts of genetic, occurrence, and environmental data often spanning centuries. These data provide significant historical context and offers a ‘snapshot’ of relevant data that allows for comparisons between contemporary and historic population and landscape trends. Here I examine evolutionary processes across different taxonomic, ecological, and time scales in Triodanis with a focus on three main objectives: 1) elucidate species level relationships for this group within the context of the larger Campanulaceae; 2) complete an updated systematic treatment for the genus; 3) finally, I explore how historic patterns of biogeography influence contemporary phylogeography in one focal species, Triodanis perfoliata. To achieve my first objective, I employed a target-enrichment approach using the Angiosperms353 probe set, which alleviates issues that arise from a lack of genomic resources (e.g., reference genome) and generates data that will be useful to the broader phylogenetics research community, alongside genus-wide morphological data to bring clarity to the relationships among Triodanis and its broader relationships within the Campanulaceae. A better understanding of the evolutionary relationships within the Triodanis genus will provide an important phylogenetic framework for ongoing and future work. To achieve objective two, I synthesized morphological data for all species of Triodanis and described each as a pragmatic species. An updated taxonomic treatment is the next logical step to best share these findings and add to the ever-growing wealth of knowledge regarding the Campanulaceae family. Finally, to achieve objective three, I expand the scale of my work through time and use contemporary and historic environmental data alongside contemporary genetic data to explore how historic patterns of biogeography shaped contemporary patterns of gene flow. Further, ongoing work in this genus has yielded insight into breeding system evolution, population biology, phenological responses to climate change, biogeography, and pollinator assembly. All of these data can be used to make genetically informed models allowing exploration of historic and contemporary patterns of phylogeography and biogeography. Contemporary patterns of genetics can help inform about changes in distribution, gene flow, population and landscape dynamics and explain the processes guiding those changes over time as well as model potential changes in the future. This can aid in making informed decisions on how a changing environment may not only affect distribution, but also population dynamics and patterns of gene flow.