Data from: A time-calibrated road map of Brassicaceae species radiation and evolutionary history

The Brassicaceae include several major crop plants and numerous important
model species in comparative evolutionary research such as Arabidopsis,
Brassica, Boechera, Thellungiella, and Arabis species. As any evolutionary
hypothesis needs to be placed in a temporal context, reliably dated major
splits within the evolution of Brassicaceae are essential. We present a
comprehensive time-calibrated framework with important divergence time
estimates based on whole-chloroplast sequence data for 29 Brassicaceae
species. Diversification of the Brassicaceae crown group started at the
Eocene-to-Oligocene transition. Subsequent major evolutionary splits are
dated to ∼20 million years ago, coinciding with the Oligocene-to-Miocene
transition, with increasing drought and aridity and transient glaciation
events. The age of the Arabidopsis thaliana crown group is 6 million years
ago, at the Miocene and Pliocene border. The overall species richness of
the family is well explained by high levels of neopolyploidy (43% in
total), but this trend is neither directly associated with an increase in
genome size nor is there a general lineage-specific constraint. Our
results highlight polyploidization as an important source for generating
new evolutionary lineages adapted to changing environments. We conclude
that species radiation, paralleled by high levels of neopolyploidization,
follows genome size decrease, stabilization, and genetic diploidization.