Shifting Distributions (IMAGE) National Evolutionary Synthesis Center (NESCent) Caption This phylogenetic tree illustrates the changes in geographic range of wing-propelled diving seabirds like the modern-day puffin and auk. Modern-day puffins and auks have long been recognized as environmental indicator species for ongoing faunal shifts, and fossil records now indicate that ancient relatives were similarly informative. Researchers have found that puffins and auks may have been at their most diverse and widespread levels during a relatively warm period of Earth's history. The results also explain how past extinctions have shaped the geographic distribution and population size of existing species. Credit Adam Smith Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.