Format: ORAL

Rebekah Mohn1,2, Rosana Zenil-Ferguson3, Thilo Krueger4, Andreas Fleischmann5,6, Adam Cross4,7,Ya Yang2

1 Center for Tree Science, Morton Arboretum, Lisle, IL, United States 2 Department of Plant and Microbial Biology, University of Minnesota–Twin Cities, St. Paul, MN, United States 3 Department of Biology, University of Kentucky, Lexington, KY, United States 4 School of Molecular and Life Sciences, Curtin University, Bentley, WA, Australia 5 Botanische Staatssammlung München (SNSB-BSM), Munich, Germany 6 GeoBio-Center LMU, Ludwig-Maximilians-University, Munich, Germany 7 EcoHealth Network, Brookline, MA, United States

DroseraL. (Droseraceae, Caryophyllales) has been long thought to exhibit large amounts of chromosome evolution due to both single chromosome number change and polyploidy. We used the BiChrom model to test whether rates of single chromosome number increase and decrease, and chromosome number doubling differed between D. subg. Ergaleium and the other subgenera and between self-compatible and self-incompatible lineages. The best model for chromosome evolution among subgenera had equal rates of chromosome number doubling but higher rates of single chromosome number change in D. subg. Ergaleium than in the other subgenera. Contrary to expectation, self-incompatible lineages had a significantly higher rate of single chromosome loss than self-compatible lineages. The findings of different rates in different subgenera were further supported by phylogenomic analyses not finding evidence for any polyploid events in the D. subg. Ergaleium while finding evidence of polyploidy in the other subgenera. We found no evidence for an association between differences in single chromosome number changes and diploidization after polyploidy or centromere type. This study highlights the complexity of factors influencing rates of chromosome number evolution. Further work should explore whether meiotic and specifically holocentric drive might explain heterogeneity in chromosome number evolution in Drosera. This work is in part published in Evolution at https://doi.org/10.1093/evolut/qpad153.