A Female Fly, Full of Fertilised Eggs, Is Swept by High

question 62

Multiple Choice

A female fly, full of fertilised 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 and their balancing organs (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.
Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridise, then which of the following statements about species W and Y are true?
I. Species W and Y have genomes that are still similar enough for successful meiosis to occur in hybrid flies.
II. Species W and Y have more genetic similarity with each other than either did with the other two species.
III. Species W and Y may fuse into a single species if their hybrids remain fertile over the course of many generations.

• A) Only I is correct.
• B) Only II is correct.
• C) Only III is correct.
• D) I, II, and III are correct.

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