AN EXPLORATION OF FACTORS DRIVING PATTERNS OF HYBRIDIZATION IN TRIODANIS

Author

Keegan Sean McConnell, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2024

Degree Name

Master of Science

Department

Plant Biology

First Advisor

Weber, Jennifer

Abstract

Elucidating and preserving biodiversity is an essential component of biological research, yet many natural processes impede our ability to define basic patterns of biodiversity. Hybridization is a common process in flowering plants, with a range of outcomes that influence our understanding of species ecology and evolution. In many systems, factors that facilitate or prevent successful hybridization are poorly understood. In this study, I investigate various potential mechanisms driving patterns of hybridization between Triodanis biflora and T. perfoliata. Previous research in this system has documented extensive hybridization, but some work has also alluded to the potential role of the breeding system in limiting gene flow. These patterns are particularly interesting given conflicting evidence about species delimitation of this group, with some considering T. biflora a subspecies of T. perfoliata. Here I employ a large-scale field study as well as previously collected genetic data and synthesize our overall knowledge of factors influencing patterns of hybridization in this system. Specifically, I demonstrate the first potential genetic signature for hybridization in this system, and confirm morphological differences between T. biflora, T. perfoliata, and putative hybrids across multiple hybrid zones. Across multiple field sites, I found no evidence for microhabitat (i.e., soil texture, light availability) or pollinator visitation rates for consistently limiting gene flow. Congruent with previous work, variation in the breeding system between T. biflora and T. perfoliata appears to play a major role in apparent asymmetrical patterns of hybridization across multiple hybrid zones. These species exhibit dimorphic cleistogamy, with T. biflora producing relatively fewer open flowers, and thus, less potential to contribute to hybrid gene flow. Overall, this research, combined with multiple previous studies, emphasizes the importance of natural history studies for elucidating these patterns. Despite considerable potential for gene flow between T. biflora and T. perfoliata, variation in the breeding system appears to effectively drive the magnitude, as well as overall patterns of hybridization in this study system.