It is one of the least studied penguin species and its population decreases due to the impact of global change – which includes the effects of climate change on the ecosystem – and the overexploitation of its food resources. Genetic analyzes are key to understanding the ability of these birds to adapt to environmental pressures. In addition, the studies show significant differences with penguins such as the Papua, another emblematic species of the white continent.
Chinstrap penguin with its young © Fabiola Peña
Penguins are not only a symbol of Antarctica: they are also important predators and bioindicators of the ecological changes of the marine ecosystem. Of the five species that live on the continent, the chinstrap is one of the two that has experienced a severe decline. Research conducted in 12 chinstrap reproductive sites in Western Antarctica and South Shetland Islands, and in a population – not studied before – of the subantarctic island Bouvet, revealed that this animal has a high diversity and genetic homogeneity due to the considerable dispersion between your colonies. However, climate change would force the chinstrap to move further to survive.
“The most commonly cited causes of the decline of this species, like the Adélie penguin, are related to climate change experienced by Antarctica. On the other hand, despite having a wide geographical distribution, from Antarctica to Bouvet Island, chinstrap penguins exchange enough individuals among the breeding colonies to avoid genetic differentiation among their populations. This result contrasts with the Papua penguin, whose colonies are isolated from each other for hundreds of thousands of years”, says Elie Poulin, a researcher at the Institute of Ecology and Biodiversity (IEB) and an academic at the University of Chile.
Juliana Vianna, a researcher at the Pontifical Catholic University of Chile, adds that “despite not having found genetic differentiation between the Antarctic chinstraps and the Bouvet Island, which is 3600 km away, we found a differentiation not very marked, but present between the colony of Georges Point, a town near the southern limit of the distribution of chinstraps in Antarctica. “
The study was recently published in the journal BMC Evolutionary Biology and counted with the participation of an international team of researchers from the Pontifical Catholic University of Chile, Institute of Ecology and Biodiversity (IEB), Pontificia Universidade Católica de Minas Gerais, Universidade do Vale do Rio dos Sinos, University of Concepción, National Museum of Natural Sciences of Madrid and the Norwegian Polar Institute.
The scientists analyzed the demographic history, the dispersion by sexes, the connectivity between the colonies and the genetic diversity of this species, evidencing the differences with the penguins of Adelia and Papua, the other two species of the genus Pygoscelis that are found in the area.
The research, funded by Fondecyt, detected a marked tendency for chinstrap females to abandon their native groups to move long distances, while the behavior of philopatry, which is when an animal returns to reproduce in the same colony where it was born, is more pronounced in males.
Poulin, who is also director of the Antarctic Ring Project about Antarctic Genomic Biodiversity, explains, “It is common to see in birds and mammals that the two sexes of the same species do not disperse in the same way. In this case, the greatest genetic difference detected in males from different colonies suggests that it is the females that tend to ensure the dispersal of their species. “
On the other hand, stressful environmental conditions not only cause the decline in the population of these birds: they would also force them to increase their movement. The effects of climate change modify, for example, ice cover, which could interfere with the reproductive behavior of chinstraps. Other consequences would be alterations in the marine trophic chain, such as the decrease of krill, the main food of Chinstrap and Adelia. Very different is the case of the Papuan, a species that has varied its diet to not depend exclusively on krill and that, unlike the other species of the same genus, has increased its population in Antarctica.
Chinstrap versus Papua
The results of the chinstrap contrast considerably with the papua, another of the penguins that has a wide distribution in Antarctica and Sub-antarctic Islands, according to a study published last year, led by Juliana Vianna. The team of scientists examined 12 colonies of this species found in Western Antarctica, the South Shetland Islands and the sub-Antarctic islands Malvinas, Crozet and Kerguelen.
Gentoo penguins © Diego Bravo
The result was surprising: the sub-Antarctic and Antarctic papua colonies have a high genetic differentiation, that is, they have very divergent lineages. While there is only one large population of chinstrap, distributed in the Antarctic and subtartactic zones, there are four populations – genetically – very different from Papua, each corresponding to one of the study sites. Therefore, each colony is exposed to different local environmental conditions. The IEB researcher states that “it is incredible what we found, because the genetic distance is enormous, we are talking about several million years of separation between the colonies, which at a genetic level could be equivalent to subspecies and even to different species”.
Unlike the chinstrap and its greater tendency to disperse and move away from its place of origin, the papua has a strong philopatric behavior, so it returns to its place of birth, which would limit the exchange of individuals between breeding colonies. The great geographical distance between the Antarctic and sub-Antarctic islands would restrict their connectivity.
In this way, the demographic history and the characteristics of the populations, revealed by the genetic studies, offer valuable clues about the adaptability and resilience that these seabirds would have against the current panorama.
“The Antarctic marine fauna and flora have been maintained for millions of years in thermally stable environments and have lost the mechanisms that allow facing important thermal variations. Assuming climatic scenarios, colonies of chinstrap penguins could move south of Antarctica and disappear from areas further north of its distribution”, says Poulin.