The Mystery Of The Galapagos Pink IguanaThe Pink Iguana, Conolophus rosada, is a bit of a puzzle. It lives only on the slope of the Wolf Volcano on the northern part of Isabela, the largest island in the Galapagos.
This population is kept isolated from the other land iguanas on the island by large cooled lava floes that the iguanas find difficult to cross.Until recently the pink iguana has been considered a subpopulation of the common yellow land iguana that lives on many of the islands. However, genetic research on the Galapagos iguana types has shown that this species is far more distantly related to the common yellow iguana than is the other known species, the Santa Fe Iguana or Conolophus pallidus. The separation of the species occurred about 5.7 million years ago. This leaves us with two problems. 1) The Age Of IsabelaThe island of Isabela is quite young in geological terms, being no older than 1.5 million years old. It is still volcanically active, and indeed the whole mass of the island is the result of six volcanoes that have joined together.
That means that these iguanas did not evolve on the island of Isabela, but must have traveled there from another island in the Galapagos chain.2) The Age Of The Ancestral IguanaAccording to genetic studies, the common ancestor for all species of Galapagos iguanas arrived at the islands some 10 million years ago. At least, that is when the split between the land and marine iguanas occurred. Yet the oldest island in the group is between 5 and 10 million years old! What Is The Explanation?The explanation for this is found in the geology of the Galapagos Islands, which are perched atop a tectonic plate intersection that spews out great amounts of lava and is continuously building new volcanoes. As the landmasses created by the tectonic activity move away from the hotspot they erode. The seas are unforgiving and without any reefs or continental shelf to protect them, the islands are hammered by storm after massive storm. These eventually break up the islands. There are a number of islands in the chain that are now only the submerged remains of once larger landmasses. As islands shrink the inhabitants have the choice of either battling it out for the remaining space and resources, or swimming to the next available landmass. Traffic Between The IslandsSo we are left with the Pink Iguana having evolved on an island that no longer exists. It must have swum to the newly made island of Isabela from one of the now submerged islands some time in the past. Indeed, given the age of the species it may have traveled across several islands on its journey to Isabela. The other yellow iguanas it shares the island with must have arrived separately as they are not found in the area of the volcano inhabited by the pink species. One can only suppose that there is a great deal of animal traffic between the islands. We may think about reptiles surviving a sea journey as an amazing event, but the history of the Galapagos makes the waters between the landmasses look like conveyor belts! Return from the Pink Iguana to The Galapagos Islands or return to the Reptiles Home Page.
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