The four-foot-tall emperor penguin of Antarctica may be the best-known member of the penguin family, but it is far from the only one. Seventeen other penguin species live throughout the Southern Hemisphere, and many inhabit isolated islands that are difficult for scientists to reach and study. That remoteness may help explain how an entire gentoo penguin species escaped recognition for so long. The birds live on the Kerguelen Islands, known in French as the Desolation Islands, nearly 2,000 miles from any permanently inhabited land mass. An international team led by researchers from Chile and the University of California at Berkeley has now identified the population as a distinct species, making it the first new penguin species named in more than 100 years. The findings were published in Communications Biology. DNA reveals four gentoo penguin species Genetic evidence shows that what scientists once treated as a single, widely distributed species of gentoo penguin is actually made up of four separate species. One of them had never been formally recognized. Aside from subtle differences in body size and vocalizations, it closely resembles other gentoos, with the familiar white belly and black back helping penguins avoid predators and hunt prey in the ocean. However, genetically it is clearly different. Scientists call this type of organism a cryptic species, meaning it closely resembles related species despite having significant genetic differences. The researchers also determined that three gentoo populations previously classified as subspecies are genetically different enough to be recognized as full species. The newly recognized southeastern gentoo penguin, Pygoscelis kerguelensis, may face an uncertain future. Two of the other newly defined species could also be vulnerable as global warming reshapes the Antarctic and sub-Antarctic regions where they live. The southern gentoo, now known as Pygoscelis ellsworthi, is the only one of the four that lives in Antarctica. Climate projections suggest that it could be relatively unaffected and could even expand its range. “In Antarctica, of course, other species, not the gentoo, are threatened by climate change,” said Juliana Vianna, one of the lead authors of the paper and a professor of ecosystems and environment at the Andrés Bello National University in Santiago, Chile. “But the gentoo is of greatest concern in the subantarctic region,” an area of widely separated islands north of Antarctica governed by numerous countries, including Chile, South Africa, France, the Netherlands, Australia and New Zealand. “It is very important that conservation institutions in all the different countries involved recognize and take appropriate measures to save these three gentoo penguin species,” he added. A century of debate over gentoo penguins To resolve long-standing disagreements over gentoo classification, Vianna joined forces with co-senior authors Rauri Bowie, a professor of integrative biology at UC Berkeley, and Elie Poulin, a professor at the University of Chile in Santiago. Together they brought together penguin specialists from around the world to conduct a broad genomic study of gentoo populations. Previous researchers had proposed up to six gentoo subspecies, but there was no universal agreement. The new work represents a consensus built from complete genome sequences of 64 penguins collected from 10 breeding colonies. For the first time, sampling covered almost the entire geographical distribution of gentoo penguins. The team also compared physical and behavioral characteristics, including coloration, calls, breeding schedules, diet and feeding behavior. “There is probably no penguin species whose taxonomy has been more debated than that of the gentoo penguin,” said Bowie, curator of the Museum of Vertebrate Zoology at the University of California, Berkeley. “For more than 100 years it has been controversial how many species or how many subspecies there are. What this paper does is try to address that question using cutting-edge integrative approaches.” How penguins spread across the Southern Hemisphere Bowie and Vianna have spent nearly a decade studying how penguins evolved and diversified. In 2019, they published research indicating that penguins originated near Australia and New Zealand approximately 22 million years ago. Emperor and king penguins subsequently split from other lineages, with emperors becoming associated with Antarctica and kings with subantarctic. About 12 million years ago, the development of the circumpolar current helped other groups of penguins spread across the subantarctic, colonizing remote islands and archipelagos and reaching as far as Africa and South America. Gentoo penguins have one important advantage over many of their relatives: they are flexible when it comes to eating. Instead of relying heavily on one type of prey, they will consume almost anything they can catch underwater. That flexibility is becoming increasingly important as krill populations decline. Penguins with more limited diets, including emperors and Adélies, are declining in numbers in some regions. In contrast, the Papuans living alongside them on the Antarctic Peninsula are increasing. Flexible Diet Helped Drive Speciation Ironically, the gentoo’s broad diet may also have helped create the distinct species recognized today. Because gentoos can feed on a wide variety of prey, including fish, krill, squid, and cuttlefish, they do not need to travel especially far from their breeding colonies in search of food. They also tend to return to the same nesting sites year after year. Over long periods, populations on isolated islands became increasingly adapted to their local environments. Those ecological and behavioral differences were gradually reinforced by natural selection on their genomes. Researchers estimate that the four gentoo species diverged over the past 300,000 to 500,000 years. Geographic isolation played a major role, along with the Antarctic Polar Front, an important boundary in the Southern Ocean where water temperature and salinity change dramatically. That limit can also restrict the movement of marine animals. North of the polar front, where the waters are warmer and saltier, lives the eastern lineage, Pygoscelis taeniata, found on Crozet, Marion and Macquarie Islands. The northern lineage, Pygoscelis papua, is restricted to the Malvinas/Falkland Islands and Martillo in South America. The recently described southeastern lineage, Pygoscelis kerguelensis, lives near the Polar Front. This relatively small population evolved on Kerguelen Island and probably on nearby Heard Island. Further south is the largest lineage, Pygoscelis ellsworthi. It inhabits the Antarctic Peninsula, coastal Antarctica and South Georgia Island. Penguin genomes reveal local adaptations The genomic analysis was led by University of Chile graduate student Daly Noll, first author of the paper. Compared to previous work, the researchers examined a much larger portion of the genome and analyzed thousands of genetic differences called single nucleotide polymorphisms (SNPs). That data revealed how each gentoo species has adapted to its particular environment. The southern gentoo, which thrives in Antarctica, carries genetic changes associated with life in extreme polar conditions. The researchers found a greater number of genes related to heat production, fat and lipid storage, and light perception. Changes related to light perception can help birds cope with dramatic seasonal changes in daylight and the intense reflection of light on ice. The East Papuan, on the other hand, has more genes associated with efficient carbohydrate metabolism and greater diving performance. These include genes involved in oxygen transport and use, blood vessel formation, mitochondrial activity and lung development. Together, those traits may allow birds to stay underwater longer while foraging in oceans with relatively low biological productivity. The northern gentoo of South America showed a different pattern. Its genome was enriched with genes involved in digestion, heart contraction and muscle arousal. The researchers say these changes may support the sustained physical activity necessary for prolonged underwater feeding. Climate change could leave island penguins stranded The team also used climate models to estimate where suitable gentoo habitat might exist in 2050. Under a moderate climate change scenario, island-dwelling subantarctic species could lose suitable habitat on all the islands where they currently live. In many cases, there would be few or no nearby islands that would offer suitable replacement habitat. The Antarctic Papua could fare very differently. Its suitable range is expected to extend further into the interior of the continent as conditions change. At the same time, emperor, Adélie and chinstrap penguins are expected to decline as sea ice disappears and krill populations growing under the ice are affected. Vianna noted that climate change is not the only danger penguins face outside of Antarctica. Warming oceans, habitat destruction, predation by rats and dogs, competition with commercial fishing, and bycatch in fishing nets also threaten many populations. “In terms of climate change, island species that have really small populations could be compared to subantarctic gentoo penguins,” he said. “The Galapagos and other island penguin species, because they are endemic to these islands, will not find a place to go after a change in their environment. Those islands are very isolated and these penguins cannot easily adapt to colonize any other region.” Genomics could help protect penguins The unusually large and diverse data set gathered for the research could prove valuable far beyond issues of penguin classification, Bowie said. Vianna is already examining penguin genomes for genetic differences associated with survival from avian influenza, a disease currently affecting penguin, bird and mammal populations around the world. Identifying genetic traits related to resistance or vulnerability could help conservationists determine which populations face the greatest danger. “Whole genome sequencing has transformed our ability to not only look at adaptation from a perspective of how things diversify, but it has really important conservation value,” Bowie said. In addition to Bowie and Vianna, the study includes biologists from Australia, Spain, Venezuela, South Africa, the United Kingdom, France, Argentina, Monaco and Brazil. Daly Noll of the University of Chile in Santiago is the first author of the paper.
