Temporal patterns of diversification in Brassicaceae demonstrate decoupling of rate shifts and mesopolyploidization events

Background and Aims Whole-genome duplication (WGD) events are considered important driving forces of diversification. At least 11 out of 52 Brassicaceae tribes had independent mesopolyploid WGDs followed by diploidization processes. However, the association between mesopolyploidy and subsequent diversification is equivocal. Herein we show the results from a family-wide diversification analysis on Brassicaceae, and elaborate on the hypothesis that polyploidization per se is a fundamental driver in Brassicaceae evolution. Methods We established a time-calibrated chronogram based on whole plastid genomes comprising representative Brassicaceae taxa and published data spanning the entire Rosidae clade. This allowed to set multiple calibration points and anchored various Brassicaceae taxa for subsequent downstream analyses. All major splits among Brassicaceae lineages were used in BEAST analyses of individually analysed 48 tribes comprising 2101 taxa in total using the internal transcribed sp...