Peripatric speciation (1 of 5)
Only a few fruit fly larvae survived the journey from the mainland to colonize the island.
Peripatric speciation (2 of 5)
These few survivors just by chance carry some genes that are rare in the mainland population. One of these rare genes happens to cause a slight variation in the mating dance. Another causes a slight difference in the shape of male genitalia. This is an example of the founder effect.
Peripatric speciation (4 of 5)
As the island population grows, the unique reproductive features on the island result in a cascade of changes caused by sexual selection. These changes optimize, or at least improve, the fit of male and female genitalia to one another and female sensitivity to nuances of the mating ritual. Flies also experience natural selection that favors individuals better suited to the climate and food of the island.