Only three populations of emperor penguins (Aptenodytes forsteri) survived during the last Ice Age (19,500 – 16,000 years ago), and the Ross Sea was likely the refuge for one of these populations, says a team of genetic researchers led by Jane Younger, a PhD student from the Australian Institute for Marine and Antarctic Sciences.
Emperor penguins (Aptenodytes forsteri). Image credit: Michael Van Woert / NOAA / NESDIS / ORA.
Emperor penguins are famed for their adaptations to their icy world, breeding on sea ice during the Antarctic winter when temperatures regularly drop below minus 30 degrees Celsius.
However, according to a study published in the journal Global Change Biology, conditions were probably too harsh for emperor penguins during the last Ice Age and that the population was roughly seven times smaller than today and split up into three refugial populations.
In their study, Jane Younger and her colleagues examined the genetic diversity of modern and ancient emperor penguin populations in Antarctica to estimate how they had been changing over time.
“Due to there being about twice as much sea ice during the last Ice Age, the penguins were unable to breed in more than a few locations around Antarctica. The distances from the open ocean, where the penguins feed, to the stable sea ice, where they breed, was probably too far,” said co-author Gemma Clucas, a PhD student at the University of Southampton, UK.
“The three populations that did manage to survive may have done so by breeding near to polynyas – areas of ocean that are kept free of sea ice by wind and currents.”
One of these polynyas that supported a population of emperor penguins throughout the last Ice Age was probably in the Ross Sea.
The team found that emperor penguins that breed in the Ross Sea are genetically distinct from other emperor penguins around Antarctica.
The findings suggest that the populations became isolated during the last Ice Age, pointing to the fact that the Ross Sea could have been an important refuge for emperor penguins and possibly other species too.
“It is interesting that the Ross Sea emerges as a distinct population and a refuge for the species. It adds to the argument that the Ross Sea might need special protection,” said co-author Dr Tom Hart from the University of Oxford, UK.
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Jane L. Younger et al. Too much of a good thing: sea ice extent may have forced emperor penguins into refugia during the last glacial maximum. Global Change Biology, published online March 1, 2015; doi: 10.1111/gcb.12882
