Quinine Tree Invasion and Control in Galapagos: A Case Study

Abstract

One of the most invasive species in Galapagos Islands is the red quinine tree, Cinchona pubescens Vahl (Rubiaceae). Though considered rare and endangered in its native range in Ecuador, quinine is being controlled as an invasive and used as a timber source in Galapagos. Introduced to Santa Cruz Island in the 1940s, it started spreading in the 1970s and now covers a vast area in the humid highlands of the island. Quinine is considered an ecosystem engineer, changing plant species diversity and abundance as well as impacting endemic birds in the invaded area. It also alters the microclimate and increases phosphorus concentrations in the soil. The production of abundant small and wind-borne seeds, paired with a vigorous vegetative reproduction, makes it a very successful invader. Quinine is manually and chemically controlled by Galapagos National Park Directorate, but this method requires constant follow-up control of seedlings germinating from the seed bank. In addition, disturbances caused by these control measures seem to facilitate the establishment of other introduced plant species, especially blackberry (Rubus niveus). The quinine invasion in Galapagos Islands provides an opportunity to help understand the ecology of plant invasions in Galapagos and in island ecosystems in general.