Final answer:
The characteristic unlikely to change in the island lizards' descendants after moving to the mainland is a change in numbers.
Step-by-step explanation:
In this case, the characteristic that is unlikely to change in the island lizards' descendants after moving to the mainland is C. A change in numbers.
Even though the lizards may face different environments and potential predators on the mainland, the overall population size is not likely to be affected as long as there is no major change in their habitat or resources. The numbers of lizards may fluctuate due to factors like reproduction and competition, but the descendants will still belong to the same species as their ancestors.