Penguin evolution linked to shifting icebergs

The breakup of giant icebergs may have forced minor evolutionary changes in penguins over the past 6,000 years, a new study suggests.
The Antarctic iceberg chunks, which break off the continent now and then, are thought to have blocked the swim paths of Adelie penguins returning home to their colonies. Some of the penguins were forced to become immigrants in other colonies, where they established new homes and interbred with the locals.
As a result, genetic changes that might otherwise have remained isolated became widespread among the different colonies. The result is what scientist call microevolution.
Penguin evolution linked to shifting icebergs – LiveScience – MSNBC.com