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, the sub-Antarctic island Bouvet), revealed that this animal has a high diversity and genetic homogeneity due to the considerable dispersion between their colonies. However, climate change would force the chinstrap to move further to survive.
THE CAUSES BEHIND THEIR DECREASE
“The mostly common 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 geographic distribution, the chinstrap penguins exchange enough individuals among the breeding colonies to avoid genetic differentiation among their populations, “says Elie Poulin, a researcher at the Institute of Ecology and Biodiversity (IEB) and academic of the University of Chile.
It is a species of penguin least studied and their population decline by the global change in the ecosystem. The overexploitation of their food resources may be also the key factor.
The specialist adds, “This result contrast with the papua penguin, whose colonies are isolated them each other from hundreds of thousands of years”.
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 in the colony of Georges Point, a locality near the southern limit of the distribution of chinstraps in Antarctica
The study was recently published in the Journal BMC Evolutionary Biology and has 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, dispersal by sex, connectivity among the colonies and the genetic diversity of this species, showing the differences with the penguins of Adelia and Papua, the other two species of the genera Pygoscelis that found in the zone.
Females abandon their natal groups
The research detected a marked tendency of the 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 Papua, 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.
“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.