Describe7 marksChallenge
A group of pelagic fish species in a deep lake is thought to have evolved from a single ancestral species. DNA sequence analysis of a conserved gene shows that species A and B are 99.8% identical, while species A and C are 98.5% identical, and species B and C are 98.4% identical. The lake has several basins separated by shallow sills; during periods of low water, the basins become isolated. Additionally, within one basin, two closely related species differ in the depth at which they feed and their spawning season.
Describe how speciation can occur through allopatric and sympatric mechanisms, using the fish scenario and DNA data to support your answer.