Biologists from Notre Dame, Michiagan State and the University of Florida have just published an article in which they describe how the introduction of apple trees to the US 400 years ago has affected the evolution of a type of fruit fly AND the parasitic wasp that feeds on the maggots of the fly.
Prior to the presence of apple trees in the US, these flies Rhagoletis pomonella found mates, and laid eggs on the fruit of the hawthorn tree. In the 1800's some of these flies began going to apples to mate and lay their eggs instead. These flies have now become genetically different from the flies that still visit the hawthorn fruit.
This is an example of how new species can form. Over time mutations, natural selection and other mechanisms of evolution affect the two fly population in different ways, until they are so genetically different they become species.
What is really interesting to me is how fast this happens, and that the same kind of speciation is also happening to the parasitic wasps that feed on the maggots of the flies. This is an example of co-evolution. Co-evolution happens when the evolution of one species affects the evolution of another.
So you see, it is not necessary to go off to some exotic place to study evolution. The process of evolution is happening all around us. Articles like this make me wonder what kind of evolution could be going on right here at the college?
Forbes et al. Sequential Sympatric Speciation Across Trophic Levels. Science, 6 February 2009: 776-779 DOI: 10.1126/science.1166981