Unravelling the Ecological and Evolutionary Mysteries of the Rough Fescue Grasses F. Hallii and F. Campestris.

Abstract

The rough fescue grasslands of western North America are diverse, unique ecosystems that provide essential ecological and agricultural services, yet have been significantly fragmented by land conversion, urbanization, and energy infrastructure. Only around 5% of their historic 137,000km^2 extent remains unmodified, and remaining prairie fragments face ongoing threat from unsustainable grazing practices, invasive crop species, and disruption of their natural disturbance regimes. Conserving and restoring rough fescue grasslands remains challenging due to the sensitivity of their defining species, the rough fescue grasses Festuca hallii and F. campestris, and a limited understanding of how rough fescue ecology and life history affects their fitness and persistence in disturbed environments. This dissertation addresses three components of rough fescue autecology that have direct applications for conservation and restoration; Chapter 2 investigates the role of dormancy and cold exposure on rough fescue seed germination using a comparative germination assay between F. hallii and F. campestris. It finds that the temperature and duration of seed storage has significant impacts on rough fescue germination, and can greatly enhance or stifle germination in seeds of the same age and provenance. Chapter 3 examines the prevalence of Epichloë fungal endophytes in wild rough fescue populations across a mosaic of disturbance conditions at Glenbow Ranch Provincial Park near Cochrane, Alberta. Here, I found high (µ >80%) levels of endophyte infection across all sites, and confirmed, for the first time, the presence of an Epichloë symbiosis in F. hallii. My final chapter explores the taxonomic and genetic relationship between F. hallii and F. campestris through a province-wide genomic survey of both allopatric and sympatric rough fescue populations. I discovered the occurrence of extensive and ongoing hybridization between the two species in their ranges of overlap, and additionally, found evidence of F. campestris introgression into allopatric populations of F. hallii. Collectively, these findings provide actionable ecological insights into the early life stages, mutualistic interactions, and genetic structure of rough fescue grasses, offering a foundation for more targeted and effective restoration practices in this imperiled grassland ecosystem.