They Look Alike, But They're Different Species... The Secret of the "Four Siblings" of Gentoo Penguins

Genetic Changes Accumulate Due to Limited Migration and Localized Habits

Scientists have used DNA analysis techniques to reveal that a penguin species, long believed to be a single species for over a century, has actually diverged into four distinct evolutionary lineages.

Gentoo Penguin. Photo by EPA Yonhap News

On September 29 (local time), international media including the Washington Post reported that an international team of researchers, through genetic analysis, had found that the Gentoo penguin has diverged into four separate evolutionary lineages over hundreds of thousands of years. The researchers concluded that each should be considered an independent, distinct species.

Known as the "gentlemen of the penguin world," Gentoo penguins inhabit the Antarctic continent and several islands in the Indian Ocean, including King George Island where Korea’s King Sejong Station is located. They have long been classified as a single species, although debate continued for years over whether Gentoo penguins should be divided into several species or subspecies. Subspecies are defined as groups within the same species that differ slightly due to their region or environment.

The research team analyzed the genomes of 64 individuals collected from 10 breeding sites and compared their habitats. In addition to external features such as feather coloration and body size, they also examined vocalization, breeding seasons, diet, and feeding behavior.

The analysis ultimately led to the classification of Gentoo penguins into Northern, Southern, Eastern, and Southeastern Gentoo penguins. Among them, the "Southeastern Gentoo penguin" was identified for the first time through this study and confirmed as a new species. The Southeastern Gentoo penguin is physically identical to other Gentoo penguins, and was therefore discovered to be a "cryptic species" that can only be distinguished through genomic analysis.

Geographical distribution of four species of gentoo penguins inhabiting the Southern Ocean. Source=Communications Biology

The researchers explained that because Gentoo penguins feed on fish, krill, and squid that are only available in their immediate environments, and have the habit of returning to the same breeding sites each year, they do not migrate over long distances. This means that as they live isolated on their respective islands, genetic changes enabling them to adapt to local environments have accumulated over time. In addition, the research analyzed that the "Antarctic Polar Front" in the Southern Ocean has also promoted species differentiation. The Antarctic Polar Front is a boundary where warm, saline waters from lower latitudes meet cold, less saline Antarctic waters, acting as a barrier to animal migration.

Furthermore, based on a moderate climate change scenario, the researchers projected that by 2050 the environments of the islands inhabited by three of the species found outside Antarctica are likely to become unsuitable for survival. The study also found that there are very few newly suitable islands nearby for potential migration. Laurie Bowie, a professor of integrative biology at the University of California, Berkeley who led the research, emphasized, “Genome analysis greatly enhances our understanding of how organisms diversify and adapt, which is critically important from a conservation perspective. At the same time, our research highlights just how urgently these fragile ecosystems need our protection.”

This project, led by researchers from the University of California, Berkeley and the Universidad de Los Lagos in Chile, involved 22 scientists, conservation biologists, and penguin experts from five continents. The results were published in the international journal 'Communications Biology.'

Meanwhile, Gentoo penguins, known as the third largest penguin species after the emperor and king penguins, typically reach heights between 51 and 90 centimeters. Male penguins generally weigh between 4.9 kg and 8.5 kg, while females are slightly smaller, usually weighing between 4.5 kg and 8.2 kg.

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