Changes in the Italian wall lizard population.
4 05 2008On the small island of Pod Mrcaru, off the coast of Croatia, scientists have managed to conduct an accidental experiment in evolutionary biology. In 1971 they transported five adult pairs of Italian wall lizards to the island to observe their adaptation to the new environment but the outbreak of the Croatian war prevented them from returning until 2004. By this time the lizard population had grown to over five thousand in number, spanning more than thirty generations. And, during this time, they have undergone some startling physiological changes.
Pod Mrcary has abundant vegetation which was thought to be an ideal habitat for the insects that the lizards prey upon. It was thought that these insects would serve as a primary food source however, nature had other plans. The lizards instead acquired completely new biological structures that would allow them to digest the abundant plant life; they developed a set cecal valves, located between the large and small intestine, which serve to slow down food in their fermenting chambers. This allows the lizards to process the cellulose and fatty acids and gives them the ability to digest vegetation. This change has also been reflected in the lizard’s phenotype. They have developed a less defensive behaviour and social structure. For example, their populations have grown in density and they are forming social groups to allow for easier reproduction.
To the scientists, the most startling aspect of this is the time scale over which this change had occurred. The lizards developed completely new structures in approximately thirty years while the conventional evolutionary thinking is that such a significant adaptation should take millions of years. If these changes can be linked to a change at the genetic level it will mean an unprecedented rate of evolutionary change. As far as I know this is work that is still being completed.
I don’t know if this will prove to be clear example of evolution but its certainly sounds like it. The experts in this field seem to be reserving their judgment and I am inclined to let them do what they do. After all, they have far more experience in this field than I. However, one thing is clear - changes, be they genetic or otherwise, have occurred in the population. I will be following this up and I hope to report more to you in the future.
[1] http://news.nationalgeographic.com/news/2008/04/080421-lizard-evolution_2.html
Tags : Biology, Evolution, genetics, Italian wall lizard
Categories : Biology, Science