Format: ORAL

Tanja Slotte1

1 Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, SWEDEN

Distyly is a floral polymorphism governed by a supergene, that has evolved repeatedly in independent flowering plant lineages, making it a prime example of convergent evolution. Distyly promotes outcrossing and efficient pollen transfer by pollinators via the presence of two floral morphs that differ reciprocally in the positions of their anthers and stigmas, coupled with a heteromorphic self-incompatibility system that reduces self- and intra-morph fertilization. While distyly has evolved multiple times, it has been lost far more frequently, often in association with convergent evolution of floral selfing syndromes. Studying the genetic basis of convergent evolution and loss of distyly therefore offers an excellent opportunity to investigate to what extent convergent phenotypic evolution is associated with repeated evolutionary changes at the molecular level, at the level of genetic architectures, regulation of molecular pathways, or in terms of selection at particular genes. Studying repeated losses of distyly further offers an opportunity to test theoretical predictions on the genetic causes of supergene breakdown, and the population genetic consequences of selfing. Here, I will present our work on these topics in Linum, a plant system that is exceptionally well suited for this purpose. Harnessing high-quality genome assemblies, we have for the first time identified and characterized the distyly supergene in Linum at the molecular level. We have also tested theory on genetic causes of loss of distyly and documented pervasive population genomic consequences of this major evolutionary transition. Taken together, genomic studies of distyly have revealed striking similarities in hemizygous genetic architectures and molecular evolution of independently evolved distyly supergenes, contributed new insights into the genetic basis of floral morphs, and provide a foundation for further characterization of the genetic underpinnings and genomic consequences of convergent evolution and loss of distyly.