The capacity for sustained adaptation in a rapidly changing environment

Australia's corals are suffering, victims of 'coral bleaching' brought on by a warming ocean. When these colourful underwater animals expel their algal partners, thereby turning white, they may be sending us two messages that could define the Earth's biota in the coming years. One is that the Earth is now warming at rates faster than it has for millions of years, and the most recent report from the United Nation's climate scientists warns that some environmental changes in response to this warming could become self-sustaining, amplifying their own effects. There is now wide agreement that global warming has been brought on by anthropogenic (human-induced) increases in greenhouse gases such as carbon dioxide, but whatever the causes, the Earth is now warmer than it has been for 125,000 years. This new climate, and the many environmental changes it brings, mean that the plants and animals are going to have to adapt to survive, and do so over timescales of potentially many hundreds to thousands of years. In this context, if coral bleaching persists, the corals eventually die.

The other message from the corals is that our current views on how rapidly species can adapt might be dangerously optimistic. Studies of species adapting in the wild, or in laboratory experiments, often reveal that species can change rapidly. They can, but these studies typically take place over a handful of generations and thereby fail to answer the question of for how long such high rates of change can be sustained. Populations of any given species naturally vary in features such as height or weight (or resistance to coral bleaching), and it is this variation that natural selection acts upon, causing change by favouring some variants over others. But as this process goes on, the natural variation gets used up, and at that point adaptation slows to a crawl, or can even stop, and species can go extinct. Already, according to the United Nations' Sustainable Development report "Nature is declining globally at rates unprecedented in human history - and the rate of species extinctions is accelerating". The tiny corals might be among the first harbingers of this effect.

For how long and at what rates can species maintain sustained bouts of adaptation? The research we wish to conduct will address this question using estimates derived not from short-term studies but from the Earth's evolutionary history. Our approach will apply new statistical modelling techniques to thousands of species to estimate their past rates of change over millions of years of evolution. From this unprecedented database we will be able to develop profiles of the amounts and upper limits of change that can be sustained over millennial timescales. Then, using information on the natural variation within populations, we will be able to determine if these historical rates of change are at their evolutionary maximums, and if not, estimate how much they could be increased.

Our work will apply these methods and ideas to species from all of the Classes of vertebrates (animals with a backbone), including mammals, birds, fish, reptiles and amphibians. We will be able to identify which kinds of species are capable of the greatest adaptive change, and whether traits like flying or an aquatic existence are associated with greater or lesser amounts of change.

Our approach is easily applied to other species, and highlights the kind of information that will be needed to make predictions about how the Earth's biota might change in response to a rapidly changing world.