July 7, 2005—This is the tale of two Himalayan snow lotuses: the heavily harvested Saussurea laniceps,left, and the seldom collected Saussurea medusa. Both are native to the eastern Himalayas where they grow in rocky habitats above 13,000 feet (4,000 meters).

S. laniceps is prized by tourists who pick the strange-looking, rare flowers for souvenirs. The flower is also in demand for making traditional Chinese and Tibetan medicines to treat headaches, high blood pressure, and menstrual problems. Because the largest flowers of S. laniceps are preferred for harvest, just before the lotus goes to seed, it is mostly the smaller specimens that are left to propagate.

Wayne Law and Jan Salick of the Missouri Botanical Garden in St. Louis studied the human impact on these plants. They compared lotuses they found in markets with museum specimens picked as long as a hundred years ago. And they looked at live plants in protected areas on a sacred mountain in Tibet.

Their conclusion, published this week in the journal Proceedings of the National Academy of Sciences, is that the heavily harvested lotus has evolved four inches (ten centimeters) shorter over the past century, threatening its fitness for survival in unprotected areas. The same trend was not seen in S. medusa, the lotus that leads a relatively unmolested existence.

The findings suggest that humans can unconsciously drive evolution, which should be considered when managing threatened species, the authors say.

—David Braun