No mountain range is more important to the Melastomataceae than the Andes. From warm foothills to cold, windswept páramo, different melastomes occupy almost every elevation band, and the family is one of the most conspicuous groups of woody plants on the slopes.
The altitude gradient
Moving upward from the lowlands, you pass through a series of zones. In each, the melastome community changes.
Foothills and lower montane forest (up to roughly 1,500 m). Warm and humid. Tall trees and shrubs in genera such as Miconia and related berry-fruited groups are common, along with some of the epiphytic genera.
Cloud forest (roughly 1,500 to 3,000 m). Cloud and mist keep the air humid and the foliage wet. The trees are shorter and covered with mosses, orchids and bromeliads. Melastomes here include shrubs and small trees such as Axinaea, and epiphytic or hemiepiphytic genera such as Blakea.
Upper montane forest and treeline (roughly 3,000 to 3,500 m). Trees become stunted and twisted. Many melastome shrubs here have small, thick, hairy leaves.
Páramo (above the treeline). Open, cold, windy and wet. Species of Brachyotum and some others form part of the shrubland.
Why so many species?
The Andes provide a mosaic of habitats packed into a small area. Steep slopes, isolated valleys and different rainfall patterns create many separate environments. Populations isolated on different slopes or ridges can diverge over time into new species. This pattern, rapid speciation in a mountain setting, is thought to have contributed to the family's diversity.
Adaptations across the gradient
- Leaf size tends to decrease with altitude, and leaves become thicker and more leathery.
- Hairiness increases at cold, exposed sites, helping insulate and reduce water loss.
- Flower and pollinator relationships shift, with more bird and bat pollination in cool forests where bees are scarcer. Some Andean melastomes use more than one type of pollinator.
Ecological roles
Melastomes are among the most common sources of fruit for birds in Andean forests, and their flowers feed pollinators. Their root systems and rapid regrowth help stabilise slopes after landslides, and they are often among the first woody plants to colonise such disturbed ground.
Threats and climate
Andean forests have been cleared for farming and grazing, and the area of intact cloud forest has shrunk. Climate change is expected to push suitable habitat upslope, a particular problem for species that already live near the top. See conservation of melastomes.
For gardeners
Many Andean melastomes need cool nights and constant moisture, which is why few are widely grown. Plants that do adapt include certain Tibouchina-type shrubs. For the naming complexities of those, read Tibouchina and Pleroma.
Takeaways
- The Andes harbour a very large share of the family's diversity.
- Different melastomes dominate each elevation zone.
- Altitude shapes leaf traits, flowers and pollinators.
- Mountain species are especially sensitive to climate and land use.