Found 2 resources for the concept: Some lineages remain relatively unchanged for long periods of time
Parsimonious explanations for punctuated patterns Punctuated equilibrium is sometimes erroneously cited as evidence that evolutionary biology still hasn't figured out how evolution works. In fact nothing could be further from the truth. Punctuated equilibrium builds on (not tears down!) established evolutionary theory. Find out how the process works. This article appears at SpringerLink.
Evo in the news: Influenza, an ever-evolving target for vaccine development Some vaccines provide lifelong protection with one or a few doses, but the flu requires a new shot every year. And in some years, the flu shot is hardly effective at all. Why is the flu vaccine different from so many other vaccines? This news brief from February 2013 provides the evolutionary explanation.