The geology also gave support to his hunch. The Andes started forming tens of millions of years ago, but it wasn’t until 2.5 million years ago that the northern Andes rose above the elevation where trees can survive. Only then could all the diversity of the Páramos emerge.

To calculate the speed of evolution in the Páramos, Dr. Madriñán and his colleagues surveyed 13 different lineages of plants that grow there. They estimated the rate at which species had split from each other in each lineage, and then combined those estimates into a single average. The scientists then looked at data on plants that grow in other fast-evolving places, such as Hawaii and the Mediterranean coast.

The results surpassed Dr. Madriñán’s suspicions. The Páramos weren’t just home to fast evolution, it turned out. Of the eight places he and his colleagues compared, the Páramos are evolving the fastest of all.

Other experts on evolutionary rates are intrigued by the new study, which was published last month in Frontiers in Genetics. “Of course these results are still very preliminary,” said Luis Valente of the University of Potsdam, noting that scientists have only sampled a few groups of plants from each evolutionary hot spot. But Dr. Valente thought the study persuasively demonstrates that the Páramos are a special place. “This may be a region where evolution is proceeding at a very fast pace, and where many new species may still be in the process of being formed,” he said.

Michael Sanderson of the University of Arizona thinks the contest won’t be settled definitively until biologists can draw large-scale evolutionary trees. “Then we’ll finally sort out the hottest hot spots,” he said.

Dr. Madriñán suspects that the peculiar climate of the Páramos is responsible for their fast evolution. Because the grasslands are at the equator, they are bathed in sunshine year-round. But to take advantage of that ample energy, the plants also have to contend with cold temperatures and harsh ultraviolet rays, not to mention weather that can turn on a dime. “You may be in total mist and then half an hour later you are in total sunshine,” Dr. Madriñán said.

When plants began to spread into the newly formed Páramos, Dr. Madriñán suspects, they evolved many solutions to surviving there. They specialized on different niches, from damp bogs to dry hillsides and stands of shrubs and trees. Páramo plants also evolved a wide range of defenses against the elements. Espeletia uribei, the daisy tree, grows white hairs on its flowers to protect them from damaging ultraviolet rays, while covering its stem with a thick layer of dead leaves to keep it warm.

Dr. Madriñán and his colleagues are now exploring the history of the plants to see if they can explain their remarkable speed. “Páramos are the new laboratory to study evolution happening at incredible rates,” he said.