New link shown between genetics, climate change and population growth in sheep

Study investigates how genetically-controlled physical traits affect population dynamics - News Release

Imperial College London News Release

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Thursday 15 March 2007

A new way of mapping the link between genetic changes and population change in animals is published in this week's issue of Science (Friday 16 March). The study shows how the distribution of genetically-controlled traits, such as size, within a population of animals has a direct impact on the growth of that population. Additionally, it suggests that the impact of these traits could be affected by changes in climate.

The study, which provides the most detailed method of examining the complex relationship between ecology and evolution, also has significant implications for understanding the impact of environmental factors, such as climate change, on populations of animals.

Researchers at Imperial College London and the Universities of Cambridge, Edinburgh and Stanford, studied a population of Soay sheep in the Outer Hebrides, and used a combination of existing population data and field observations to track how changes in the distribution of sheep in the population influenced fluctuations in the overall size of the population. They found that in years with harsh winters that the population grew fastest when there were many large individuals within the population. However, this effect disappeared in recent years when winters were more favourable.

Dr Tim Coulson , from Imperial College London's Division of Biology, explains how this relationship between genetic traits and changes in the population could be linked to climate change: "Data shows that in the 1980s big sheep were genetically favoured in this population, as big sheep had more chance of surviving the Outer Hebrides' harsh winters.

"But as the climate changes and the Soay sheep are not subject to such tough winters, there will be reduced natural selection for larger animals. This could mean that if the climate in this region of Scotland continues to change, there will be changes in the size of sheep due to natural selection which could have a significant impact on the population dynamics of the Soay sheep overall."

The study has shown that population change is affected by body size, and that body size, in turn, is affected by a number of factors including genetics, environmental factors including climate, and the availability of food. As such, the researchers have been able to link together, for the first time, the big ecological picture with the genetic make-up of individual animals.

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Notes to editors:

1. 'The evolutionary demography of ecological change: linking trait variation and population growth', Science, Friday 16 March 2007.

Fanie Pelletier (1), Tim Clutton-Brock (2), Josephine Pemberton (3), Shripad Tuljapurkar (4), Tim Coulson (1).

(1) Division of Biology and the Natural Environment Research Council (NERC) Centre for Population Biology, Imperial College London, Silwood Park, Ascot, Berkshire, SL5 7PY, UK.
(2) Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK.
(3) Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK.
(4) Department of Biological Sciences, University of California, Stanford, CA 94305-5020, USA.

2. About Imperial College London

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