One of the most important traits of organisms is body growth and its ontogenic changes throughout thier lifes. In reptiles, body size has been correlated with survival and reproduccion success, and this in turn are vital for their fitness. In turtles for examples there are evidences in which the bigger is the female, the more eggs they lay and the bigger eggs are. Thus if a species is able to have a higher reproduccion success then their chances to live more years on earth are bigger.

It is amazing to me how organisms are born with an ability to grow more or less depending on the environment where they are, a mechanism known as body growht plasticity. Other factors may make this ability less flexible, more canalized, more fixed, such as the sexual dimorphism of the species. In some cases males are larger than females and the opposite pattern also exists. Whether this pattern is maintained under different experimental conditions is the subject of my current research.

With this question in mind, I am running two common garden experiments with 2 river turtle species with oppostie sexual dimorphism patterns, and fascinating life histories. The first one is the Common Snapping turtle, Chelydra serpentina, with males bigger than females; and the second is the Arrau or Giant Amazon rive turtle, Podocnemis expansa, with females bigger than males. The first species is a living dinosaur that resembles a war tank walking on the bottom of the rivers. The second is a younger species, skillful swimmers that inhabit the Orinoco and Amazonas rivers of South America.