We believe that the St. Kitts rodent, thanks to natural selection and several different series of mutations, were able become superior tree climbers. Our belief is that some sort of directional selection was occuring, where rodents with longer limbs were able to more easily escape predators. As a result, the average limb length of the St. Kitts population began to increase in comparison to the Nevis population.
While we have not been at St. Kitts long enough to identify a specific gene (or set of genes) that differs from the rodents on Nevis, we believe that a mutation occured in the St. Kitts population. This mutation could have allowed the St. Kitts rodent to grip and climb trees with greater dexterity. Over many generations, the rodents were able to spend significantly longer periods of time in trees. Their superior jumping abilities would have allowed them to travel quickly and also evade predators.
Come back soon to hear more about the Nevis population of rodents!