Europe PMC · 2026-05-13
Researchers traced the evolutionary history of a quirky reproductive strategy in the oak family (Fagaceae), where some species wait an entire extra year between pollination and fertilization. They found this "slow fruiting" evolved once in a common ancestor and has been lost multiple times independently in groups like oaks, chestnuts, and chinkapins.
The two-year fruiting strategy evolved just once in the common ancestor of most Fagaceae (excluding beech and Trigonobalanus), making it an ancient single-origin trait.
At least three lineages — Castanea (chestnuts), Quercus (oaks), and Castanopsis (chinkapins) — independently reversed back to the faster one-year fruiting cycle.
Insect pollination and evergreen leaf habit were ancestral to the subfamily Quercoideae, but neither trait statistically drove transitions in fruiting strategy, suggesting the two-year delay evolved and is maintained by other selective pressures.
