Format: ORAL

Pengchuan Sun, Susanne S. Renner*, and Jianquan Liu Pengchuan Sun1, Susanne S. Renner2, and Jianquan Liu1

1 College of Life Sciences, Sichuan University, Chengdu, China 2 Department of Biology, Washington University, Saint Louis, USA

Chromosome-scale genomes provide a basis for inferringancestral linkage groups and processes of karyotype evolution. We have reconstructed the karyotypes of numerous representatives of the major groups of flowering plants, using an approachthat starts from retained intact chromosomes and syntenic blocks.The results show thatthe most recent common ancestor of the flowering plants had 16 unique protochromosomes and that nine of these protochromosomes are still retained inat least oneextant species without any fusion or fission. Other protochromosomes underwent rare and probably irreversible fusion events,detectable through repeated polyploidizations.Amborella trichopodashares a uniquenested chromosome fusion withNymphaeacolorata,Euryale feroxand otherNymphaeales.Our data also securely resolve the position of the monocots as sister to magnoliids plus eudicots. These findings reject thelow ancestral numbers for ancient angiospermsinferred with non-genomic approaches over the past 90 years and have profound implications for the early evolution and biogeography of flowering plants.