Examples of turtles not common at the reserve. Simón, Nicolás and Carlos photographed these Pseudemys sp. and Terri found this Graptemys sp a short time ago. All of them exotic. The genera Pseudemys and Graptemys are native to North America and belong into the family Emydidae.

Turtles of the genus Graptemys are known as map turtles for the patterns on the carapace, difficult to see in adults. They are easy to tell from Pseudemys and Trachemys because their carapace is keeled along the center.

Like too many animals turtles are subject to traffic or commerce as pets. that is why it is easy to find feral individuals spread very far from their range. Unluckily owners may lose interest in the pet and release it anywhere not being aware of the consequences: outcompeting native species for food or other resources, causing or carrying diseases, hibrization with related native species with the subsequent genetic contamination and loss of the native genotype. 
Fot this reason exotic turtles are isolated from native ones

But there is another exotic turtle much easily seen: the red-eared turtle Trachemys scripta. 

The genus Trachemys also belongs into the family Emydidae, but unlike the other two its area of distribution is along America. The problem with this turtle is that it hibridizes with our native Trachemys the painted turtle Trachemys dorbigni. At the reserve individuals with mixed characteristics (hybrids) have been found. Neither genetic nor biological studies have been carried out, so there is no evaluation on the real impact of this exotic turtle

Red-eared turtle
Trachemys scripta elegans

Until recently these two Trachemys had been considered subspecies. You may possibly find them in some texts as Trachemys scripta elegans (red-eared turtle) and Trachemys scripta dorbigni (painted turtle). Since our native turtle is widely separately from other subspecies of Trachemys scripta it has been raised to species level and today the painted turtle is Trachemys dorbigni.

Differences between these two Trachemys. The red-eared turtle Trachemys scripta elegans has a postocular red line which is interrupted, whereas our native painted turtle Trachemys dorbigni has a yellow line which continues in a narrower line. The plastron is mainly light coloured in the red-eared turtle and dark-coloured in the painted turtle.

In Argentina there is not only legal import but there are also breeding centers (of any of the above mentioned), which increases the number of individuals in the ecosystem and makes matters worse. Studies by UNC and Conicet researchers have evaluated the risk some areas like Mesopotamia are exposed to since this ecosystem provides optimal conditions for these turtles to thrive. They suggest regulatory programs should be made effective to prohibit commerce and breeding of exotic turtles and thus reduce the loss of biodiversity and the economic and ecological impact.