EPOW Ecology Picture of the Week -- Mutisia of Argentina

Explanation: We are in the steppe country of southern Argentina -- the temperate Patagonian highlands, to be exact. Before us is a beautiful and interesting plant, a mutisia.

What makes this plant so interesting -- botanically, at least -- is its growth habitat and life history. It grows as an epiphyte that climbs over and eventually kills its shrub host, much as Ficus trees in the tropics start as epiphytes in other tree canopies and then grow to encase and eventually kill their hosts. This particular mutisia (in the photo at right) is growing on a native plant called an orange ball tree (Buddleja globosa).

So should mutisia be classified as a vine, a shrub, an epiphyte, or a parasite? Or all of these? Actually, the correct classification is hemiepiphyte, or a plant that is an epiphyte for only part of its life.

In the high Andes of Chile, some 10 species of the genus Mutisia exhibit a most remarkable sequence of growth habits: 4 species of Mutisia lack tendrils (twining and grasping structures) at the end of the leaves and occur as free-growing plants; 1 species has only hooks and grows either as an epiphyte or free-growing plant; and 5 species have specialized tendrils at the leaf apices and grow as epiphytes on other shrubs. Perhaps this array of growth forms also mirrors the evolution of the epiphytic forms.

The unopened flower buds and opened flowers of this particular mutisia were covered with tiny red and black ants, making me wonder what ecological role the ants may be playing with the plant ... perhaps pollinators? or defenders? Was this a commensal (one-way) benefit? Were the ants just harvesting nectar? Or perhaps a two-way mutualist relation, with the plant receiving some benefit in return, such as defense against herbivores or a pollination service?

Acknowledgment: My thanks to botanist Andy MacKinnon for identification and guiding me to this wonderful steppe location in Argentina.

EPOW - Ecology Picture of the Week