Isolation and sexual adaptability contributed to the evolution of thousands of palm species.
Coupled with the negative effects of global cooling, angiosperms pushed gymnosperm extinction past the point of recovery.
Did the Cyatheaceae become such a diverse family slowly over time, or in spurts? The largest molecular sampling yet points to gradual accumulation of species.
Normally you would expect organs to change across evolutionary time. However, this is not always the case, and some clades can be species-rich, but still have very similar flowers.