106 NCEA Style Question: Speciation

1. Killer whales (Orcinus orca) are found throughout the world's oceans. Researchers have identified that different killer whale populations follow different types of hunting behaviour. In the waters around Antarctica, five populations have been identified (F to J). DNA evidence indicates these populations began to diverge about 250,000 years ago.

Population F prefers to hunt seals on pack ice Population G's preferred prey is penguins Population H hunts minke whales Population I prefers to hunt Patagonian toothfish Population J hunts Antarctic toothfish.

Researchers believe that these killer whale populations are showing sympatric speciation.

Discuss sympatric speciation using the killer whales as an example. In your discussion include: • how sympatric speciation occurs • the relevant reproductive isolating mechanisms • an explanation of how sympatric speciation differs from allopatric speciation. • a justification as to whether or not sympatric speciation is indeed occurring in killer whales.

Distribution of killer whales in Antarctic waters

J F H G

Source: R. Riesch, Sci. American, Nov. 2016, pp. 54-61

I