A new autumn has brought another burst of red and yellow leaves. And it has also brought an interesting new idea about why trees put on this show every year.
In recent years, scientists have been roughly divided into two camps when it comes to autumn leaves. One camp holds that autumn colors are just part of preparations for winter. The other holds that the colors are a warning to insects to stay away.
The warning hypothesis came from the late biologist William Hamilton. He pointed out that trees fight off insect larvae with toxins. A more vigorous tree could produce more toxins than a weaker one. It could also produce more vibrant colors in the fall by producing more pigment molecules. (The red in leaves is created by molecules called anthocyanins, for example). Perhaps a tree could send a message to insects looking for a place to lay their ...
