bioRxiv preprint doi: https://doi.org/10.1101/737155; this version posted August 15, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. Ancestral reconstruction of sunflower karyotypes reveals dramatic chromosomal evolution Kate L. Ostevik1,2, Kieran Samuk1, and Loren H. Rieseberg2 1. Department of Biology, Duke University, Durham, NC, 27701 2. Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4 Correspondence to:
[email protected] 1 bioRxiv preprint doi: https://doi.org/10.1101/737155; this version posted August 15, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 1 Abstract 2 3 Mapping the chromosomal rearrangements between species can inform our understanding of genome 4 evolution, reproductive isolation, and speciation. Here we present a systematic survey of chromosomal 5 rearrangements in the annual sunflowers, which is a group known for extreme karyotypic diversity. We 6 build high-density genetic maps for two subspecies of the prairie sunflower, Helianthus petiolaris ssp. 7 petiolaris and H. petiolaris ssp. fallax. Using a novel algorithm implemented in the accompanying R 8 package syntR, we identify blocks of synteny between these two subspecies and previously published 9 high-density genetic maps. We reconstruct ancestral karyotypes for annual sunflowers using those 10 synteny blocks and conservatively estimate that there have been 9.7 chromosomal rearrangements 11 per million years – a high rate of chromosomal evolution.