Suppose that a few individuals of a lizard species are transported on a log that floats from the mainland, where the lizard is abundant, to a distant island, where prior to this event no lizards (of any species) existed. the environmental conditions on the island are similar to those on the mainland. a small population of this lizard becomes established on the island; within a few years, allele frequencies in the island population differ greatly from those in mainland populations. what is the most likely cause of the genetic differences between the island and mainland populations?