Seals brave climate change and win
Some of Earth's creatures lost the fight against climate and habitat change thousands of years ago, but the southern elephant seals proved they had the evolutionary and demographic edge needed to survive. New international research shows these seals established a new breeding site thousands of kilometres from existing breeding grounds in order to save themselves. The findings were published in the journal Public Library of Science (PLoS) Genetics. The researchers from Italy, South Africa, the UK and the US discovered that the elephant seals, Mirounga leonina, adopted the emergent habitat and established a new population that thrived when the Antarctic ice sheets of the Ross Sea Embayment retreated in the Holocene period almost 8 000 years ago. The team collected southern elephant seal skin samples and carried out DNA (deoxyribonucleic acid) extractions and PCR (polymerase chain reaction) setup from the ancient remains of the seals at a DNA laboratory at the University of Durham in the UK. The results showed that this Antarctic colony showed high levels of genetic diversity; their extensive population size is what probably helped. By tracking the evolutionary and demographic processes of these seals, researchers can give predictive data in response to potential future impacts such as those triggered by climate change. 'In general, this approach of looking to the past to understand what might happen in the future, has good potential for predicting the impact of environmental change in both marine and terrestrial systems,' explained co-author Professor Rus Hoelzel from the University of Durham. 'We've shown how a highly mobile marine species responded to the gain and loss of new breeding habitat. The new habitat was quickly adopted, probably because seals migrate annually into Antarctic waters to feed,' he added. 'However, when the ice returned and the habitat was lost, only a small proportion returned to the original source population. The Antarctic population crashed and much diversity was lost.' According to the researchers, the use of ancient mtDNA (mitochondrial DNA) and evolutionary models helped them track the population dynamics of the colony, as well as the connectivity between this and modern breeding sites. 'Using ancient DNA, we were able to track the dynamics and diversity of a population from its foundation, through to its extinction, in the context of Holocene climate change. We learned that [a] new habitat emerging within the species' migratory range could be quickly taken advantage of, but that the reverse was not true,' Professor Hoelzel said. The study showed that the researchers discovered signs of rapid expansion in the new colony 8 000 years ago, which was then followed by directional migration and a loss of diversity 1 000 years ago. The information obtained indicates that the new colony seals were originally from Macquarie Island in the Pacific Ocean. 'The movement patterns of seals from this Antarctic breeding site would have been unlikely to take them near other potential breeding sites, and so when their breeding site was lost, their numbers crashed,' he commented. 'The seals that discovered the new breeding site had things good because food was abundant and nearby; however, when the ice returned, the new colony collapsed and only a few seals made it back to their original home,' he added. 'This illustrates the importance of understanding the behaviour and life history of a species, in order to model how it may be able to respond to rapid change.'
Countries
Italy, United Kingdom