Format: ORAL

Yanqian Ding1,2, Pete Hollingsworth2, Alex Twyford1,2

1 Institute of Ecology and Evolution, The University of Edinburgh, Edinburgh, UK 2 Royal Botanical Garden, Edinburgh, UK

The evolution of modern plant diversity is intricately linked to the dynamics of mating systems and genetic diversity. This study investigates the genus Euphrasia, known for its rapid speciation and diverse mating strategies, to understand these factors roles in shaping plant diversification. We focus on a comparative analysis of Euphrasia micrantha, a predominantly selfing species, and E. arctica, a mixed-mating species, exploring their genetic structures, diversity, and runs of homozygosity. Our results indicate that E. micrantha, despite its high inbreeding levels, maintains nucleotide diversity comparable to the genetically more diverse E. arctica. This suggests that occasional outcrossing events may play a crucial role in preserving genetic diversity within selfing species. Additionally, the pronounced genetic structure observed in E. micrantha is consistent with expectations for selfing species. The runs of homozygosity analysis in both species reveal a full spectrum of demographic history related to inbreeding, indicating complex evolutionary strategies for sustaining diversity. This study enhances our understanding of the evolutionary mechanisms that drive plant diversity, especially in lineages undergoing rapid diversification. By integrating molecular phylogenetics with population genomics, our research sheds light on the intricate interplay between mating systems, genetic drift, and hybridisation in the evolution of modern plant diversity.