Why do plants produce caffeine?

Question

Plants that are not even closely related produce the same chemical- why is that? And what is its adaptive significance? It's not a toxin, and it doesn't seem like other animals besides humans are drawn to it.

Answer 1

It is an alkaloid, which either paralyses or kills insects feeding off the plant. It is a natural pesticide, like tannins in trees.

Alkaloids are usually nitrogen-based chemicals. Because of their structure, they frequently interact with enzymes, giving them toxic properties. Another example is solanine found in nightshades.

I'm not certain why so many plants can form it. It's probably to do with an evolutionary cycle. A common ancestor produced it, and it was found to be efficient in protecting the plant, therefore natural selection made it prevalent. Afterwards, the plants mutated, giving rise to different genera, and creating the plants we know today.

Or it could be due to the metabolism of the species. Maybe caffeine production is quite efficient. It would explain why there are so many plant toxins; each plant would have its own type of metabolism and its own type of protection. Caffeine, solanine, atropine, tannins, they are all toxins used to protect the plant. And they would all be produced through different means.

Answer 2

For the plants, caffeine acts as a natural pesticide. It paralyzes and kills insects that attempt to feed on the plants.

Answer 3

It is an alkaloid that acts as a natural pesticide.