Darwin Strikes Again

Integrative organismal biology (IOB). Not a term you hear everyday, but it refers to a part of biology that focuses on the ecology, behavior, and evolution of organisms. My paper for today is about the IOB of marine iguanas, a species closely related to the green iguanas I am working on (Wikelski and Romero, 2003). The study used a method of predicting evolution as the basis for its work. The idea is that if you study the performance of specific organisms you can determine which factors play a role in the selective process of evolution and then use these factors to predict how the species will evolve in the future. 

This study, "Body Size, Performance and Fitness in Galapagos Marine Iguanas," used foraging and reproductive performance as the factors to predict evolution. The reason marine iguanas were chosen as the model is because the body mass of iguanas on different islands can vary by one order of magnitude, adult iguanas really have no predators, and they don't compete with other vertebrates for food (iguanas eat the red and green algae revealed at low tide). This means that there is a ... regulated form of evolution occurring. The changes taking place are based on the iguanas alone, not on other species. 

The study found that larger marine iguanas, male or female, had better reproductive success. The females because they could produce larger babies which were more likely to survive and the males because they were able to control a larger territory and put on a better show for thefemales. However, being large comes with draw backs. The larger iguanas had far less foraging success. They had to expend more energy to move their larger masses, it takes more energy to heat a larger body (the whole cold blooded issue), and in the end, they had trouble getting enough food. When times were good, and algae abundant, the larger lizards did fine. However, when times were bad, like after a hurricane, it was the big lizards that died. 

The conclusion that was drawn from this data is that marine iguanas will continue to get bigger. Not only does reproductive success increase, but the world is getting warmer and that's good for the cold blooded species. However, their size will be regulated by the lack of foraging success. Bigger lizards need more food and sometimes it's just not there. Don't expect any giant iguanas anytime soon. 

AA

Wikelski, Martin and L. Micahael Romero. "Body Size, Performance and Fitness in Galapagos Marine Iguanas." Integrative and Comparative Biology(2003) 43.3: 376-386. Web. 4 Apr 2012.