The Importance of Color.

Hey ya'll

I'm going to talk about evolution again today... or rather more specifically, how the evolution of certain species of lepidoptera can be used as indicators of environmental quality. Now I'm sure - and I make this reference because it is considered a textbook example of what I'm talking about here - of the peppered moth (Biston Betularia) and how it has evolved since, to cope with living through urbanization, a process that has changed drastically the habitat of which the moth is accustomed to surviving in.

Peppered Moth (Biston Betularia) typica morph.

In it's original form, the peppered moth is fairly light in color. Often white/off-white in base with a smattering of black or gray spots, the moth's coloration enabled it to blend quite efficiently among the bark of lichen covered trees in England. Indeed though it may be argued that darker individuals existed within the moth populations, the presence of light colored lichen on the trees meant that dark colored individuals were quick to be picked up by birds and a retrospective estimates reduce the presence of the dark allele in peppered moths to about 0.01%. However, at the turn of the century during the industrial revolution, many of the trees were blackened with soot. Indeed it could be said that sulfur dioxide and the emission of other forms of pollution killed of much of the light-bodied lichen that used to grow on tree bark. This in turn caused the light colored moths (which were more plentiful then) to be quickly picked off by birds. The dark colored moths, on the other hand, were able to camouflage quite efficiently against the bark of the now blackened trees.

Peppered Moth (Biston Betularia) carbonaria morph

Though the dark colored moth became the obvious survivor in post-industrial England, light colored individuals still continued to be produced as the majority of individuals in the species, but as more and more of them failed to survive due to predation, the dark colored variation of the species started to flourish. As a result, by 1895, the dark colored moth turned into the dominant color variation of the species, the frequency of the dark allele having risen to 98% (some 1000%) from it's original frequency of 0.01. Indeed, this example of evolution, involving the darkening of color as a result of increased levels of pollution and rapid changes in animal habitat have been termed "industrial melanism". Interestingly enough, I was observing two of my recently hatched chrysalids the other day. One chrysalis was taken from the infamous "weed patch" (of which I have written most fondly about on more than one occasion) located near the industrial part of Sunway, the other from the other equally famous "hutan" or "forested area" where I got most of my butterflies from. Indeed one of the interesting things I noticed when they emerged was the significant difference in coloration.

Tawny Costers (Acraea Terpsicore) *left* taken from industrial area, *left* taken from hutan.

Indeed I was so excited! Perhaps coming across an instance of industrial melanism as well... turns out though, it was simply a male and female butterfly showing characteristic sexual dimorphism. Oh well. On another note, Ray and I finally made that long awaited trip to IKEA and managed to procure for me a display case for my mounted specimens. I spent almost 4 hours last night, prepping the case and arranging the butterflies but it was most certainly worth it! More on that later though, because I want to dedicate an entire post to it. Till next time...

As an afterthought, I wonder if the diversity in human skin colors can perhaps be attributed to something akin to the situation of the moth... though not necessarily pollution, but the drive to survive. After all, if we were all descendant from Africa - assuming we possessed much darker skin tones in our primitive form - then would it not be plausible to assume that the 'white' skinned variety of human would be seen to be something more novel and/or desirable among the otherwise 'common' dark-skinned majority? But that thought leads to near to the path of racial essentialism (something we should avoid at most costs!) and that is something I shall not delve on for too long.