This is a picture of autumn in Tierra del Fuego. On the front of the photo, we see the tree species Nothofagus antarctica, forming a little scrub.
I've read what little reaserch I could find on the ecophysiology of autumn color. I know there are two main competing hypotheses: first one, red color appears as mechanism to protect leaves from sun radiation as the leaves finish to move nutrients to the trunk; second one, leaves turn red to discourage aphids and other insects to lay eggs on those trees.
As you can clearly see in the picture, and I can attest for this, different trees of the same species exhibit different autumn coloration, from no anthocyanins (yellow leaves), going all the way through orange until red. And no, yellow trees won't produce red color later on the season.
So my question is: why, if making this pigments demands resources from the plant, does this species produce it even though yellow trees still survive as the rest. From my field trips, the proportions are roughly, 30 to 40% yellow, 30-40% orange, 30-40% red and about a 10% of deep burgundy almost "purple". And if there's an actual advantage to being red, why don't all, or almost all trees, produce it?
Do we see this behaviour in northern hemisphere species? For example, do we see all colors in red maple? In birch? Because from what I understand, a single species produces almost the same autumn hue across the vast, vast majority of its trees. There isn't a noticeable proportion of yellow red maples or red birches in the wild, or is it?
by Jolly_Atmosphere_951