Why did kumquats evolved to handle 15F/-9C when its fruits freeze easily?

[lajos93]

To make the tree essentially tolerant to pretty deep freezes, yet its fruits to die at barely around -1C/-2C temps

Is it because normally the fruit matures before winter where the plant is originated from?

[pagnr]

Fruits are vehicles for seed, for dispersal and protection. The seed probably don't die at minus 1 inside a fruit. Maybe the shrivelling reduces moisture and increases the % of other pulp components / anti freeze protection for the seed ??

Also the Fortunella have been around a long time, so maybe the cold tolerance evolved as things changed, but the fruit was still effective in its function.
There might be competing influences or directions on how the plants foliage and fruit adapts or reacts to the environment.

[bussone]

To make the tree essentially tolerant to pretty deep freezes, yet its fruits to die at barely around -1C/-2C temps

Is it because normally the fruit matures before winter where the plant is originated from?

The plant doesn’t need every year’s seeds to succeed to propagate itself.

Many plants will abort their fruit/seeds if conditions become adverse.

[CeeJey]

Occasional bad winters over time would have winnowed out the plants that couldn't handle periodic freezes. Citrus lives for decades so one lost year at creating seeds isn't the end of that genetic line, but the plant freezing to death would be.