Penguins not originated in Antarctica | Polarjournal
Other than previously assumed, penguins do not originally come from Antarctica, but, starting from Australia and New Zealand, settled on the white continent a little later. Photo: Dr Michael Wenger

For a long time scientists thought that penguins originated in Antarctica and spread from there northwards, even into the tropics. An international team of researchers has now succeeded in proving, on the basis of genetic analyses, that the development of the flightless birds began in the cool coastal regions of Australia and New Zealand some 22 million years ago.

Eighteen different species of penguin now live on all continents in the southern hemisphere – from the 30-centimeter-long little penguin Eudyptula minor in New Zealand to the 120-centimeter-tall emperor penguin Aptenodytes forsteri in Antarctica. Once successful in conquering various habitats, many penguin populations are now threatened. For example, breeding colonies of emperor penguins had to relocate due to retreating sea ice and last year there was a mass death of Adélie penguin chicks on the Antarctic continent. The Galápagos penguins living at the equator suffer from El Niño events which are becoming more frequent. And in New Zealand, the little and yellow-eyed penguins must be protected with fences against feral cats, while the populations of South African penguins are declining more and more due to warming waters.

“Right now, changes in the climate and environment are going too fast for some species to respond to the climate change.”

Juliana Vianna, Professor of Ecosystems and Environment at the Pontifical Catholic University of Chile in Santiago

“We are able to show how penguins have been able to diversify to occupy the incredibly different thermal environments they live in today, going from 9 degrees Celsius in the waters around Australia and New Zealand, down to negative temperatures in Antarctica and up to 26 degrees in the Galápagos Islands,” says Rauri Bowie, professor of integrative biology at the University of California , Berkeley, and curator at the Museum of Vertebrate Zoology in Berkeley. However, these adaptations to the different habitats took place over millions of years.
“Right now, changes in the climate and environment are going too fast for some species to respond to the climate change,” says Juliana Vianna, professor of ecosystems and the environment at the Pontifical Catholic University of Chile in Santiago and lead author of the new study published this week in the journal Proceedings of the National Academy of Sciences.

Galápagos penguins have ventured farthest north and benefit from cold, nutrient-rich water that comes to the surface off the west coast of the western Galápagos Islands. However, increasingly frequent El Niño events are making life more difficult for them. Photo: Julia Hager

Where did penguins come from?

For the new study, Vianna, Bowie and their colleagues at museums and universities around the world collected blood and tissue samples from 22 penguins representing 18 species, and then sequenced and analyzed their entire genomes to record the movements and diversification of the penguins over the millennia.

With the results they answered long-standing questions: Where do penguins have their origins? And when? The first penguins were found about 22 million years ago along the coasts of Australia, New Zealand and on the nearby islands of the South Pacific. Their findings from genetic analyses suggest that the ancestors of the king and emperor penguins, the two largest species living today, split off early from the other penguins and migrated to sub-Antarctic or Antarctic waters, presumably to take advantage of the rich food resources.

Evolutionary history of the penguins: The red arrows mark the four fossil calibration points. The letters show the geographical distribution of each species, which can be read in the map on the lower right. The historical temperature of the Southern Ocean is shown as a white diagram behind the family tree. The dotted orange line marks the onset of the Antarctic Circumpolar Current. Graphic: Vianna et al. (2020),Proceedings of the National Academy of Sciences

This scenario is consistent with the controversial hypothesis that the emperor and king penguins – the only two species of the genus Aptenodytes – are the sister group of all other penguin lines.

“It was very satisfying to be able to resolve the phylogeny, which has been debated for a long time,” says Bowie. The debate was about the placement of emperor and king penguins: are they closer to other penguin lines within the family tree, or are they sisters of all other penguins? The new phylogeny confirms the latter, which Bowie says fits the penguins’ rich fossil history.

The evolution of the other penguins received a boost when 12 million years ago the Drake Passage opened completely and the swimming birds conquered the entire Southern Ocean with the help of the Antarctic Circumpolar Current, from which they colonized both the cold sub-Antarctic islands and warmer coastal areas of South America and Africa, where cold, nutrient-rich ocean currents predominate.

Distribution of penguin species living today:

Antarctica: Chinstrap, Adélie, gentoo, macaroni and emperor penguins
New Zealand: Yellow-eyed, little, Fjordland and Snares penguins
Australia: Little penguin
Macquarie Islands: Crested, Eastern rockhopper, gentoo and king penguins
Antipodes and Bounty Islands: Eastern rockhopper and erect-crested penguins
Campbell and Auckland Islands: Erect-crested, Eastern rockhopper and yellow-eyed penguins
Kerguelen, Crozet, Prince Edward Islands: Macaroni, Eastern rockhopper, gentoo and king penguins
South Sandwich Islands: Chinstrap and gentoo penguins
South Georgia: Macaroni, gentoo, chinstrap and king penguins
South Orkney Islands: Chinstrap, Adélie and gentoo penguins
Falkland Islands: Southern rockhopper, Magellanic, gentoo, macaroni and king penguins
Tristan da Cunha: Northern rockhopper penguin
Southern Chile and Argentina: Magellanic, Southern rockhopper and macaroni penguins
Northern Chile and Peru: Humboldt penguin
Galapagos Islands: Galápagos penguin

Thanks to recently developed powerful analytical techniques, researchers have been able to determine that several groups of penguins have interbred during their evolutionary history. By exchanging genetic material, penguins may have shared genetic traits that have facilitated their diversification across the strong temperature and salinity gradients found in the Southern Ocean. The most hybridized are rockhopper penguins and their close relatives, who have experienced at least four transfers of genetic information over millions of years.

In addition, the team also identified genetic adaptations that allowed the penguins to thrive in new and challenging environments. They identified changes in the genes responsible for regulating body temperature, which enabled them to adapt to Antarctic sub-freezing temperatures and tropical temperatures near the equator. Further adaptations were made in oxygen consumption, which allowed them to dive deeper, and in osmoregulation, so that they could survive in seawater without having to find fresh water.

The scientists also found that the populations of most penguin species were largest during the last ice age 40,000 to 70,000 years ago.

The largest of all penguin species, the emperor penguin, immigrated to Antarctica, probably in search of nutrient-rich waters. Photo: Heiner Kubny

DNA from the most isolated birds on Earth

For this study, lead author Juliana Vianna took blood samples from penguins in Chile and Antarctica herself and collected further samples of distant species from colleagues in France, Norway, Brazil, Australia, the United States and South Africa. Only in the case of the yellow-eyed, crested and fjordland penguins did she have to rely on material from preserved animals.

For each of the penguin species, the researchers created a reference genome as part of the study, which enabled them to date and clarify the relationships between the species. This enabled them to refute a work published last year which suggested that the closely related king and emperor penguins were a sister group to the gentoo and Adélie penguins.

Vianna and Bowie now have genome sequences from 300 individual penguins and are diving more deeply into the genetic variations within and between the different penguin populations. They recently discovered a new penguin line that is waiting for their scientific description.

“Penguins are very charismatic, certainly,” Vianna said. “But I hope these studies also lead to better conservation.”

Julia Hager, PolarJournal

More on the subject:

error: Content is protected !!
Share This