Rough-skinned newts produce a strong toxin called TTX as a defense mechanism against predators. Garter snakes can tolerate a very limited amount of the toxin. However, several populations of garter snakes have recently shown an increased tolerance for TTX. The different populations of snakes have independently acquired a gene variation that allows them to better block the effects of the toxin.
This increased tolerance for TTX in certain populations of garter snakes is a classic example of natural selection in action. In this case, the snakes that were able to tolerate the toxin had a survival advantage over those that could not, as they were able to safely consume the rough-skinned newts without being harmed by the toxin.
Over time, this advantageous trait spread through the population as those snakes with the gene variation reproduced and passed it on to their offspring. This is a clear demonstration of how genetic variation within a species can lead to different adaptations that allow certain individuals to thrive in specific environments.
The evolution of increased TTX tolerance in these garter snake populations is also a great example of coevolution, where two species have evolved in response to one another. As the newts evolved to produce the toxin as a defense mechanism, the garter snakes in turn evolved to tolerate higher levels of the toxin, creating a dynamic balance between predator and prey.
Overall, this example highlights the complex and fascinating ways in which organisms can adapt and evolve in response to their environment and the other species they interact with.