Complex sentence: Within 20 generations the 90% of the males on Kauai have "flatwings", it has reduced predation since the fly cannot locate the males and the males have adapted their behaviour, exploiting males that can make sound to attract mates for them.
Split into simpler sentences: Within 20 generations the 90% of the males on Kauai have "flatwings"; the mutation has reduced predation since the fly cannot locate the males. The males have also adapted their behaviour, exploiting males that can make sound to attract mates for them.