Natural selection sculpts genetic information to limit diversity

A study of butterflies suggests that when a species adapts, other parts of its genetic make-up  can be linked to that adaptation, limiting diversity in the population. While we cannot forecast the future, an emerging idea is that mutations that have no effect on survival today may be a source of beneficial variation in the future - Simon Martin A study of tropical butterflies has added to growing evidence that natural selection reduces species' diversity by moulding parts of their genetic structure, including elements that have no immediate impact on their survival. The research, by a University of Cambridge-led team of academics, focused on genetic data from South American Heliconius butterflies. It showed that when these butterflies develop a beneficial adaptation through a mutation in their DNA, other parts of the same chromosome - the long strings of DNA that make up the butterfly's genome - may end up being defined by the fact that they are "linked" to the point where the mutation took place. Natural selection ends up influencing the fate of these linked sites, even though they have no impact on the species' fitness and long-term survival prospects. As the adaptation is passed down through the generations as a result of natural selection, this collection of linked genetic sites can be passed on intact, removing genetic variation that previously existed in the population at these sites. This effectively limits the overall amount of variation in the butterfly population.