Evolution’s hotspots

Speciation occurs faster in unique Andean region

Biologists at the University of the Andes in Colombia claim to have discovered one of the fastest evolving ecosystems on the planet. This rapid diversification is taking place in the mountainous ecosystems of South America known as páramos.

A páramo is a grassy area above the tree line. They can be found in the Northern Andes of Colombia, Venezuela, Peru, and Ecuador occurring at altitudes of 9,200-14,800 feet above sea level. Santiago Madriñán, the lead author of a new paper in the journal Frontiers in Genetics on the evolution of plant species in the páramos, described them as “islands in a sea of forest.”

Páramos have also been described as the “water towers” of South America, absorbing large quantities of water through the soil during the rainy season and then releasing it during the dry season to nearby creeks. Páramos account for two per cent of Colombian landmass yet provide water to 70 per cent of the population. These unique ecosystems have 3,431 different species of vascular plants, almost all of which are exclusive to the region. According to the new paper, these species are evolving at an unprecedented rate.

Evolution can occur at various speeds. The process of “adaptive radiation” is an example of rapid evolution. Adaptive radiation occurs when an ancestral population of a species encounters a new environment, consisting of unfulfilled ecological niches, forcing the rapid evolution of many new species.

The finches found by Charles Darwin on the Galápagos Islands are a popular example of this phenomenon. A single species of South American finches, with beaks suited for consumption of seeds, began to occupy the islands and quickly—in geological terms—diversified into 14 different species with beaks suited for different needs, such as consumption of leaves, or insects.

It is important to note that the oldest of the islands in the Galápagos is 4.2 million years old, a drop in the bucket in evolutionary terms. By comparison, it was only 2.6 million years ago that the development of the páramo ecosystem became possible in the Andes, meaning the observed diversity emerged in this relatively short time period.

Madriñán and other researchers compared 13 different lineages and examined the rate at which species of plants had diverged from one another within these lineages. Using an average and then comparing to other evolutionary rates elsewhere in the world, they were led to conclude that speciation “occurred more rapidly in páramos than in any other hotspot on earth.”

The position of the Andes at the equator (which provides large amounts of sunlight for energy), as well as the cold temperatures and excess UV radiation, makes for a unique climate. Madriñán believes this climate may explain the speed of evolution in this ecosystem. Madriñán’s research on this hotspot of evolution opens the door for further research on the effects of climate change on plant populations, as well as the processes by which speciation occurs.