|MadSci Network: Evolution|
I always preface evolution questions with this: evolution is a theory and like all theories in science, it is inherently wrong. HOWEVER, this is also a theory's greatest strength; when proven wrong, it is retooled or even abandoned for a newer theory which more accurately describes the data. Therefore a theory of evolution can itself evolve!!!!
That being said, let's take a look at your question. The key qualifier is what you state in the first few words: genetic diversity. This in itself is a form of evolution/natural selection. If the being that prefers light is in some way more adaptable to its surroundings due to its preference for light, then it will replicate its genes and the preference could be passed on to the next generation [note the word COULD...you might want to peruse some material on gene dominance regarding passing of traits. A good place to start is here: Access Excellence: Dominant and Recessive genes
Here's another example of your proposal [aka the Peppered Moth example]: in a new city most of the buildings are white and clean. Birds who hunt moths have a difficult time catching light colored moths on these buildings due to the appearence of the city, so they tend to live longer and propagate more light colored moths. Now, if the city began to become dirtied by pollution, the buildings would become darker and the light colored moths easier to catch. When this happens, the darker colored moths would live longer because THEY would now be harder to see.
But what I think you are getting at is the creationist front that cross species breeding disproves evolution. From my understanding of natural selection and evolution, cross species breeding and/or species creation is not necessary for evolution. In my opinion, this is a interpretation difference of Darwin's work! My experience has been that evolution occurrs within a species and evolutionary changes need not create a new species to be considered evolutionary.
The fact that you were able to create your own version of Darwin's natural selection is an impressive one to say the least! For more on Darwin, start here: http://www.lucidcafe.com/library/96feb/darwin.html#booksby...
Peter 'Galapagos' Naegele
In the case of an insect, the "preference" would, no doubt, be genetic, in so far as insect nervous systems are, in general, hard wired. That being said, the scenario you give is reminiscent of reproductive isolation. That is, if the light-liking insects are more likely to mate with other light-liking insects because of frequency of encounters, it is very possible that eventually, the sexual encounters between light-liking and dark-liking insects will become statistically insignificant. The result being that the two subpopulations can become reproductively (and thus genetically) isolated. Evolution theory predicts that any time two populations become genetically isolated (for ANY reason), continuous genetic drift will, over a long time, produce two separate species. For examples of this, check out the previous answer at: 875114237.Ev
Try the links in the MadSci Library for more information on Evolution.