A research group led by Prof. ZHANG Guojie from Kunming Institute of Zoology of the Chinese Academy of Sciences conducted a study spanning all recent penguin taxa to understand 60 million years of penguin evolutionary history. The study, published in Nature Communications, sheds new light on the evolutionary pathways that allowed some land animals to transition back into aquatic environments, particularly extremely cold ones such as the seas around Antarctica.
Genomic signatures of population history and gene flow between closely-related penguin species reveal a pattern consistent with widespread refugia/recolonisation during recent climate oscillations in the Southern Ocean.
The full genomes of all extant penguin species and recently extinct species, combining with the fossil data, provided a unique opportunity to fully resolve the process leading to the penguin speciation and extinction events. The common ancestor of extant penguins appeared about 14 million years ago, after which changes in climate and environment drove the rapid speciation within crown penguins.
These data also help to reveal the detailed evolutionary process of individual genes and the gene flows between lineages, and provide new insights into the genetic basis for penguin evolution and adaptation. Among these were a suite of genes that likely underpin the highly specialized secondary aquatic adaptations seen in penguins today, including those related to thermoregulation, oxygenation, diving, vision, diet, immunity, and body size.
Besides, this study showed unexpected results. Penguins and their sister group (Procellariiformes) have the lowest evolutionary rates among birds, which may represent the culmination of a gradual slowdown associated with increasingly aquatic ecology. Evolutionary rates and temperature are positively correlated in penguins, suggesting that large-bodied, Antarctic species may be more equipped to adapt to new environments under future climate change scenarios.
Overall, this study helps to resolve the enigma of how penguins transitioned from being terrestrial to marine birds, and how they colonize some of the most extreme environments on Earth. It also showed that penguins have adapted to an ever-changing world during the past 60 million years and people can potentially remain optimistic about their future.
