Published online 15 April 2003 | Nature | doi:10.1038/news030414-3


Great Wall blocks gene flow

Chinese landmark has driven plants apart.

Insect pollinated plants are more likely to share genes across the wall.Insect pollinated plants are more likely to share genes across the wall.© GettyImages

The Great Wall of China, built to hinder marauding tribes, hampers the flow of plant genes too. Members of the same species growing on either side are genetically different, a new study of the Juyong Guan region has found.

Plant populations are known to diverge like this when their habitat is divided by a natural barrier, such as a mountain range or glacier. The changes in genetic make-up seen along the Great Wall are likely to have occurred over the past 600 years, since the time of the Ming Dynasty, which built this section of wall.

The differences "show how rapidly changes in [plant] populations can occur", comments Peter Raven of the Missouri Botanical Gardens in St Louis.

Hongya Gu and her team from Peking University in Bejing studied plants from three sites 70 kilometres north of Beijing. At two of the sites, the terrain is separated by the wall, which is six metres high and just as wide. At the third control site, a narrow mountain path runs through the vegetation. The team analysed 416 DNA samples from six species with different habitats, pollination styles and reproductive systems.

Plants isolated by the Great Wall are genetically more diverse than their unconfined counterparts, the team found1. The habitats on separate sides of the wall can be subtly different, so "one would presume that these differences are adaptive", says Raven.

“One would presume that these differences are adaptive”

Peter Raven
Missouri Botanical Gardens

Insects seem to do a better job of delivering pollen and shuffling genes between neighbouring plants than the wind. On the same side of the wall, insect-pollinated plants such as the woody shrub Vitex negundo are genetically more varied than wind-pollinated plants, such as the Siberian elm (Ulmus pumila) the study found.

"Honeybees can cross the wall easily," says Gu, so compared with wind-pollinated plants, insect-pollinated species are more likely to share genes across the wall.

The earliest record of the Great Wall is from 656 BC. Since then, many Emperors in successive dynasties have extended or renovated it. The Ming section of the wall was built between 1368 and 1644. It is over 5,000 kilometres long, incorporating watchtowers and cannon, and snaking across some of China's most forbidding terrain. 

Missouri Botanical Gardens

  • References

    1. Su, H et al. The Great Wall of China: a physical barrier to gene flow?. Heredity, 90, 212 - 219, (2003). | Article | ISI | ChemPort |