Lizards, Limbs, And Important Lessons
In a rare opportunity to study how a species evolves, scientists introduced pairs of anoles on islands in the Bahamas, where no lizards existed. They watched the lizard population grow and adapt. And what they found is fascinating.
Biologists at the University of Rhode Island conducted this interesting experiment over several years. They selected, at random, male and female pairs of the brown anole lizard from an island in the Bahamas called Iron Cay. Then they chose seven smaller islands whose lizard population had been completely wiped out by a hurricane. These seven islands were all similar to each other, but very different to Iron Cay (where the lizards came from). Iron cay was forested, but these islands were full of scrubs.
Now, whether the lizards came from forests or whether they live in scrubs has a very important bearing on how they look. Those from forests (like the initial population) have longer hind limbs, to help them climb over branches and so on. Those in scrubs have shorter hind limbs.
So what would happen if the forest species were introduced into scrubland? Would the length of their hind limbs change – with time and over generations? This would be an example of natural selection – where the best genes, adapted for survival would be passed on from generation to generation.
The other question that the scientists asked were around what is called the “founder effect.” The population of lizards on these test islands started from a very small number of individuals. Founder effect basically shows that if the starting (founding) population is small, there will be very little genetic variation in the lizards in following generations.
Both these hypothesis were proved right! While several generations of the lizards with longer limbs still have on average long limbs (founder effect), the hind limbs did grow shorter and shorter (natural selection).
Moreover, the number of lizards did not die off even though the genetic variation was small. Usually, a low genetic variation is of grave danger to a population since any disease can potentially wipe out the entire population.
This study has been hailed as an important one as it illustrates evolutionary concepts in real time. The fact that the lizards survived for so many generations could also mean that a good population can be produced from a small number of individuals. Of course, the subsequent generations have to be well protected and allowed to thrive.
Scientists hope that this study can guide us in preserving dwindling or near-extinct species.