Afemale fly, full of fertilized eggs, is swept by high winds to an island far out to sea. she is the first fly to arrive on this island, and the only fly to arrive in this way. thousands of years later, her numerous offspring occupy the island, but none of them resembles her. there are, instead, several species, each of which eats only a certain type of food. none of the species can fly, for their flight wings are absent, and their balancing organs (in other words, halteres) are now used in courtship displays. the male members of each species bear modified halteres that are unique in appearance to their species. females bear vestigial halteres. the ranges of all of the daughter species overlap. if these fly species lost the ability to fly independently of each other as a result of separate mutation events in each lineage, then the flightless condition in these species could be an example of