Format: ORAL

Ashwini V. Mohan1, Marcial Escudero2,3, Andr Marques4, Kay Lucek1

1: Biodiversity Genomics Laboratory, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland 2: Department of Plant Biology and Ecology, University of Seville, 41012 Seville, Spain 3: Department of Integrative Ecology, Doñana Biological Station, CSIC, 41092 Seville, Spain 4: Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany

Speciation is a fundamental evolutionary process that has generated and maintained biodiversity. The evolution of reproductive barriers completes speciation, and is therefore key to maintaining species boundaries. In monocentric species, where chromosomes contain a single centromere region, changes in karyotypes often promote reproductive isolation by causing constraints during cell division; however, such chromosomal rearrangements are less likely to be established first. Holocentric species that lack a single centromere but have centromere-like structures across their chromosomes have repeatedly evolved in the tree of life and often show high variation in karyotypes between closely related species. Sedges are a holocentric group with a high diversity of karyotypes between and within species. In sedges, karyotypic changes through chromosomal fusion and fission are associated with changes in transposable elements (TEs). However, the specific underlying genomic architecture is not yet fully understood. Here, we used pairs of sibling species from the genus Carex (Cyperaceae) with different or identical karyotypes to unravel the genomic architecture of chromosomal fission and fusion. For this, we (i) characterized the TEs across rearranged and non-rearranged chromosomes, (ii) measured synteny across species with different karyotypes, (iii) annotated genomes, and (iv) tested whether non-conserved genomic areas differed in gene density compared to conserved regions. We assembled 10 reference quality genomes from eight Carex species using PacBio Revio and 3D genome-wide chromatin interactions. Through this rare comparative study, we provide detailed insights into genome evolution in holocentric species and its links to speciation by tracing the evolution of changes in genomic architecture and regions associated with reproductive isolation.