Thinking about evolution and the features that lead to continuation of species, and wondering about the whiteness of a birch tree. I think it must confer some type of advantage to the organism or it wouldn’t have survived to this point. Is there a generally accepted explanation of this aspect of this plant? Does whiteness provide some degree of protection from predatory insects, etc.? Curious.
This question interested me, so I googled “why is birch bark white” and here is the #1 hit:
Why are Paper Birches so White? | Autumn 2010 | Articles | W.
Tl;dr: the whiteness of paper birches as an evolutionary adaptation is thought to be in order to prevent the cells of the dormant trees from suffering too much temperature fluctuations during sunny winter days. This gives birch trees an advantage in northern climates.
Seems to be because birch trees are widespread in higher latitudes (polar and subpolar), where dark bark would lead to high temperature differentials between those sides exposed to the Sun and the other sides. Why are Paper Birches so White? | Autumn 2010 | Articles | W
I suppose that’s the best of the current hypotheses. Of course, one has to wonder why other trees with darker bark that also grow quite far north and encounter wide temperature swings also don’t suffer from the same problems. Maybe it’s the combination of the lighter color and the thinness of the bark. Thanks.
Mutations that are passed on genetically don’t necessarily create an actual advantage for the species. As long as they don’t create a disadvantage that prevent individuals from reproducing, those mutations will continue to be passed along to future generations, advantageous or not. White bark on birch trees may not be particularly advantageous, but is certainly not a disadvantage to any significant degree.
I agree with Stana_Claus that not every trait has to be adaptive. For a further treatment of this idea, see ‘spandrel’: