Only time can tell: studying long-term evolutionary dynamics using biological archives

In the race between environmental change and evolutionary processes which is more likely to win in an increasingly changing world?
Rates of biodiversity loss are greater than at any other time in history. This loss has been linked to human activities such as gas emissions increasing global warming, use of pesticides and herbicides leading to eutrophication and pollution, urbanization and deforestation leading to habitat fragmentation. Because of this rapid environmental change exasperated by human activities, resilience of natural populations is at risk. Yet, we know remarkably little about the mechanisms of resilience, and how to predict when it might occur. This is because long-term studies are lacking. To circumvent the lack of long-term studies, the use of ‘space-for-time’ is often adopted, although this substitution is quite controversial.
Travelling back in time to study processes that triggered evolutionary responses and led to population persistence is impossible unless we chose the resurrection route, by which organisms from different times in the past are brought back to life and their evolutionary responses measured. This sounds like Jurassic Park but it is possible for a number of organisms, including the waterflea Daphnia. Daphnia is a keystone specie in inland water habitats and adopts an amazing life strategy which involves the production of resting eggs in times of stress. Many of these eggs become buried in the mud at the bottom of lakes before they have a chance to hatch and they remain viable for decades or centuries. The study of these eggs trapped in the mud enables us to study population persistence under pressure from past environmental changes. Capitalizing on the unique system Daphnia, we made enormous progress in understanding genetic and plastic responses of this keystone species to climatic and other anthropogenic changes. We were able, for the first time, to show that evolutionary rescue, a mechanism by which natural populations can outpace environmental change and avoid extinction, can happen in nature. Data we are generating will enable us to understand parallel evolution and the genetic basis of adaptation, as well as to predicting species survival in the face of anthropogenic changes. Time travelling using resting eggs may be the most poweful way of tracking long-term evolutionary dynamics in response to environmental change.