Data from: Natural hybridization between genera that diverged from each other approximately 60 million years ago

A fern from the French Pyrenees—×Cystocarpium roskamianum—is a recently
formed intergeneric hybrid between parental lineages that diverged from
each other approximately 60 million years ago (mya; 95% highest posterior
density: 40.2–76.2 mya). This is an extraordinarily deep hybridization
event, roughly akin to an elephant hybridizing with a manatee or a human
with a lemur. In the context of other reported deep hybrids, this finding
suggests that populations of ferns, and other plants with abiotically
mediated fertilization, may evolve reproductive incompatibilities more
slowly, perhaps because they lack many of the premating isolation
mechanisms that characterize most other groups of organisms. This
conclusion implies that major features of Earth’s biodiversity—such as the
relatively small number of species of ferns compared to those of
angiosperms—may be, in part, an indirect by-product of this slower
“speciation clock” rather than a direct consequence of adaptive
innovations by the more diverse lineages.