Genome sequencing has demonstrated that besides frequent small-scale
duplications, large-scale duplication events such as whole genome duplications
(WGDs) are found on many branches of the evolutionary tree of
life. Especially in the plant lineage, there is evidence for recurrent WGDs,
and the ancestor of all angiospermswas in fact most likely a polyploid species.
The number of WGDs found in sequenced plant genomes allows us to investigate
questions about the roles of WGDs that were hitherto impossible to
address. An intriguing observation is that many plant WGDs seem associated
with periods of increased environmental stress and/or fluctuations, a trend
that is evident for both present-day polyploids and palaeopolyploids
formed around the Cretaceous–Palaeogene (K–Pg) extinction at 66 Ma.
Here, we revisit the WGDs in plants that mark the K–Pg boundary, and
discuss some specific examples of biological innovations and/or diversifications
that may be linked to these WGDs. We review evidence for the
processes that could have contributed to increased polyploid establishment
at the K–Pg boundary, and discuss the implications on subsequent plant
evolution in the Cenozoic.