Final answer:
The presence of banded snakes on Kelley's Island and the Bass islands is most plausibly due to natural selection, where banded patterns offer survival advantages. Genetic drift could also influence the prevalence of this trait in an isolated population. While introduction by migration or human action is possible, the snakes' survival suggests adaptation to the island environment.
Step-by-step explanation:
The most plausible explanation for the presence or perpetuation of banded snakes on the islands of Kelley's Island and the Bass islands in Lake Erie would likely be a result of natural selection. This process involves the differential survival and reproduction of organisms due to variations in their traits, which may provide a survival advantage in their specific environment. The banded pattern could help the snakes blend into their environment, avoiding predators and catching prey more effectively. Given that the islands are isolated environments, genetic drift could also play a role in the prominence of these traits. Genetic drift is a mechanism of evolution that refers to random changes in the frequency of alleles within a population, which can be particularly pronounced in small, isolated populations such as on islands.
While migration from the mainland or human intervention could introduce a species to an island, if the banded snakes are now a stable, reproducing population on these islands, it's more likely due to natural selection favoring their banded pattern in that environment over other patterns. One can draw comparisons to other island biogeography cases, such as the brown tree snakes in Guam or the finches on the Galápagos Islands, where introduced species become successful in new habitats due to a lack of local predators and the ability to exploit available resources efficiently.
Moreover, examples from real-world scenarios such as the brown tree snakes' invasion of Guam and the Nile perch in Lake Victoria showcase how introduced species can significantly impact local ecosystems. These cases demonstrate how species can extend their range due to human activity and have far-reaching consequences for biodiversity and the survival of endemic species.