Format: ORAL

Campos-Dominguez L1,2,3, Thea E. Kongsted1, 4,Turnbull L1,2 , Fan C1, 2, Miller C1, 2, Cure L1, Downie M 5, Qi Y1, 2, Tseng Y-H6,7, Hu D6,8, Chung K-F6, Pellicer J8,9, Bombarely A10, Twyford AD1, Kidner CA1,2.

1. School of Biological Sciences, University of Edinburgh, Edinburgh, UK 2. Royal Botanic Garden Edinburgh, Edinburgh, UK 3. Centre for Research in Agricultural Genomics, Bellaterra, Barcelona, Spain 4. Gregor Mendel Institute of Molecular Plant Biology, Viena, Austria 5. John Innes Centre, Norwich, UK 6. Biodiversity Research Museum, Academia Sinica, Taipei, Taiwan 7. National Chung Hsing University, Taichung City, Taiwan 8. Royal Botanic Garden Kew, Richmond, London, UK 9. Institut Botanic de Barcelona, Barcelona, Spain 10. Instituto de Biologia Molecular y Celular de Plantas, Valencia, Spain

Understanding the drivers of species diversity and rapid radiations has always been a major goal in evolutionary biology research. Begonia is one of the most species-rich angiosperm genera with over 2000 pantropically distributed species currently identified. Recent work on Begonia provides a robust phylogenetic background for the analysis of evolutionary patterns across various radiations in the group, and suggests that speciation in Begonia is not only driven by adaptive processes, but rather by a random walk. This group exhibits large variation in chromosome number and genome sizes across the genus, and previous genomic studies also confirm abundant and recent transposon activity in some Begonia species. We have analysed patterns in TE content and activity of all main radiations within Begoniaceae using the five previously published Begonia genomes and seven new genome assemblies. We show that Begonia species show more complex, repetitive and dynamic genomes overall than their close relative, the monotypic Hillebrandia sandwichensis and identify repeat families recently expanded in species from two different highly speciose South-East Asian sections and in two large Neotropical radiations. We examined in detail two of these parallel radiations represented by two highly species-abundant sections, one in SE Asia and the other in the Neotropics. Results show recent LTR and wide satellite DNA expansions across very recently diverged species, in contrast with their species-poor, closely related clades. The genomic analysis of Begonia heracleifolia accessions showing variable genome sizes revealed a markedly higher satellite repeat and LTR-Gypsy content in the accessions with larger genome sizes, associated with the expansion of a few abundant repeat lineages. We finally identify an association between changes in genomic repeat content and genetic barriers to reproduction within this species, directly linking expansions of repetitive DNA to the process of genetic isolation and speciation.