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 (3 of 5)
These small differences, which are rare on the mainland, drift to fixation in the small population on the island over the course of a few generations (i.e., the entire island population ends up having these genes).