A month ago today our volcano, Tungurahua, exploded with so much energy the debris reached 47,000 ft into the sky. It was one of the most magnificent events in its recent history. And unlike the July event, which was invisible to us because of low clouds, this eruption pierced a crystal blue sky, near sunset. Everything came together to make this one of the most beautiful yet terrifying scenes imaginable.
The ash cloud from this eruption was especially thick. It fell as far away as Quito a hundred miles to the north, and Cuenca several hundred miles to the south, closing the Cuenca airport. Our reserves once again received only a light dusting of ash, as most of it flew high above our heads. I watched from my house five miles from the crater, and got no ash at all. Juan Pablo Reyes, our reserve manager, was on the next mountain to the east, Chamana, where we have a small reserve, and where he has his own property (which he also runs as a reserve). From there he witnessed the glowing mouth of the volcano as the sun set.
Spectacular though it was from the perspective of a singe human lifetime, this eruption was just a burp, from a geological perspective. At least twice in geological history this volcano has completely self-destructed: once about 3000 years ago, and once about 75000 years ago. Such massive eruptions would have destroyed all life on the upper parts of the volcano, probably down to 2500-3000m (the current volcano summit is at 5020m). Since evolution takes longer than that to make a new species, we’d expect there should not be species of plants strictly endemic to the high parts of the volcano. Nevertheless a few new species had been discovered there. One, discovered in 1984 by Alex Hirtz, was named after the volcano: Lepanthes tungurahuae. As expected, I eventually found it at high elevations on many of the surrounding mountains, and even much farther away.
Geology and history often limit the possibility of strict endemism in the high parts of these mountains. Not only volcanic eruptions but also climate change can push incipient new species off these mountains. The layered, datable pollen record at the bottom of Andean lakes (such as Laguna Yaguarcocha in northern Ecuador) shows in detail how vegetative zones moved up and down these mountains in the recent past, by as much as 500-1000 meters. Species that require high elevations would be eliminated from the peaks of the highest mountains during warm times (one such warm period occurred just 2000 years ago). On the other hand, species from slightly lower elevations would be able to spread off a single peak and reach neighboring peaks during the cold periods, as vegetation bands lowered and patches of cold-loving montane forests coalesced at less-fragmented lower elevations. All of these processes, and more, affect the distribution of endemic species in today’s forests. We are trying to sort them out by looking closely at the evolutionary radiations of species endemic to our area. I’ll write more about this in later posts.