Persistence in a Fragmented Habitat: Genetic Diversity and Pollination Patterns in Asclepias viridiflora

Habitat fragmentation poses many risks for plant populations, including reduced biodiversity and extinction (Fahrig, 2003; Wilson et al., 2016). This process may also have population genetic consequences as populations are reduced in size and isolated for generations. These consequences include reduced genetic variability from bottlenecks and genetic drift, the formation of spatial genetic structure, and reduced seed and pollen dispersal due to spatial isolation. While there is substantial evidence for these impacts in case studies of natural plant populations (Jacquemyn et al., 2010; Herrera and Garciá, 2010; Mannouris and Byers, 2013; Walisch et al., 2022), there have been an increasing number of studies portraying resistance to genetic declines amidst extensive fragmentation (Craft and Ashley, 2007; Kramer et al., 2008; DiLeo et al., 2017; Kubota et al., 2023). Thus, widespread predictions of negative fragmentation impacts may not be applicable to all circumstances. Many factors may govern resistance and vulnerability to fragmentation, such as time since fragmentation, cloning, and pollinator identity and specialization. While fragmentation affects all terrestrial ecosystems, grasslands, particularly Midwestern prairies have nearly disappeared due to exponential crop development and other land use changes. Therefore, case studies into grassland plant populations have become increasingly valuable to conservation practices. In chapter one, I discuss the potential genetic impacts of fragmentation on plant populations and factors that may determine resistance or vulnerability to this process. I also outline the importance of population genetic investigations in grasslands. In chapter two, “Persistence in a Fragmented Habitat: Genetic Diversity and Pollination Patterns in Asclepias viridiflora”, I present an empirical investigation of population genetic parameters and pollen dispersal patterns to characterize the effects of fragmentation in a population of Asclepias viridiflora. As the conservation and restoration of grasslands gain momentum, the research presented in this thesis will hopefully lead to better-informed practices. Here, we demonstrate that small plant populations existing in fragmented conditions cannot be overlooked, as they may retain genetic variation, remain connected through extensive gene flow, and support native pollinator communities.