Islands in the tropical sky
In the Serra da Mantiqueira mountains of southeastern Brazil, a unique ecosystem exists on granite and syenite peaks that rise above the surrounding Atlantic Forest. These are the Campos de Altitude, or high-altitude grasslands, which typically occur above 2,000 meters. Located within Itatiaia National Park, Brazil's first national park created in 1937, these grasslands represent isolated environments akin to islands. The park's highest point, Pico das Agulhas Negras, reaches an elevation of 2,791 meters (9,157 feet).
The geological foundation of these "sky islands" is the Itatiaia Alkaline Massif, an elongated igneous rock body stretching 30 kilometers. This massif, formed between 67.5 and 71.3 million years ago, is primarily composed of nepheline syenite and granite. This ancient, hard rock has resisted erosion, leaving exposed peaks that experience a harsh climate distinct from the lower forested valleys. Temperatures can be up to 10°C lower than surrounding lowlands, with frequent frosts during winter. This climatic isolation on a geologically distinct substrate allows for unique evolutionary pathways.
Laboratories of evolution
The Campos de Altitude are living laboratories for the study of island biogeography and evolution. During the Pleistocene epoch, when global temperatures were cooler, grassland vegetation was more widespread across central Brazil. As the climate warmed, forests expanded up the mountainsides, restricting the cold-adapted grassland species to the highest, coolest peaks. This process left relict populations isolated on different mountaintops, each beginning a separate evolutionary trajectory.
This isolation has led to a high degree of endemism, with many plant and animal species found only on these specific peaks. The region has many bryophytes (mosses and liverworts), with the greatest moss endemism known in Brazil. A study of endangered bryophytes in Itatiaia's Campos de Altitude found 64 distinct species, with 43 considered vulnerable and 3 critically endangered. The birdlife is also distinct, with species adapted to the high-altitude environment, such as the Itatiaia Spinetail (Asthenes moreirae). The distinct flora and fauna on each peak, despite similar environmental conditions, show allopatric speciation, where geographically isolated populations evolve into different species.