Evolution in the Galapagos Tortoise vs. Evolution in the St. Louis Box Turtle

The Galapagos tortoise is a model example of evolution, as noted by Charles Darwin during his journey to the Galapagos Islands. As mentioned in an earlier post, the Galapagos Islands are an archipelago, meaning that there is water separating the various land masses. As Darwin journeyed through the Galapagos, he noticed that the various tortoises had different shaped shells depending on which island they lived on. There was no mixing of genes from island to island because it was far too difficult for tortoises to migrate through the water separating the land masses. Therefore, the tortoises began to evolve into different subpopulations, and the most easily noticeable consequence of the evolution was the differences in the tortoise shells. For example, some were saddle-shaped and some were dome-shaped. An example of the evolution of the various tortoise shells can be seen in the below image.

Figure 1: Various shell shapes of the Galapagos tortoise

Just how the Galapagos Islands are an archipelago, Forest Park in St. Louis, MO can be looked at in a similar way. Land masses are separated by buildings, golf courses, and roads, which is essentially causing the turtles to migrate elsewhere. Turtles have been found in places they had never been seen before, such as the outer edges of Forest Park, and researchers in the St. Louis Box Turtle Project are wondering if this is due to loss of habitat because of human impact. Whatever the reason, though, it is important to wonder that if the turtles can no longer migrate throughout the park, will the same evolutionary phenomenon happen to the box turtles as it did to the Galapagos tortoises? It is too early to tell (because evolution is a very long process spanning over many, many generations), but maybe the box turtles of St. Louis Forest Park will begin to evolve into subpopulations with different adaptations that are better suited for the area of the park that they inhabit. If conservationists do not do anything to help the turtles migrate and continue gene flow, then eventually, we will no longer see any mixing of genes and passing down of helpful adaptations in the turtles. 

Figure 2: Box Turtle (Terrapene)

Information from: American Museum of Natural History

Images from: Google Images