I wonder also if dark bark might function similar to dark fur and feathers in some animals. On turkey vultures, the dark feathers help kill parasites by heating up in the sunlight. There’s a general trend in the patterns of animal colors where species in humid, tropical climates tend to be darker than in arid climates (this is called Gloger’s Rule). As with turkey vultures, the idea is that darker colors heat up more, which can help to kill parasites, which are a bigger problem in humid, tropical areas. This might also be true for trees with darker bark, where the heating affect kills off ectoparasites. I’ve reached out to the authors of this paper on Gloger’s Rule in plants (plants in hot, dry environments, like the desert, tend to be white and downy to help reflect sunlight), and will follow up if I get a response.
In the next post, we’ll look at cases in which having cooler bark is advantageous.