Effects of alien plant invasions on native vegetation remnants on La Réunion (Mascarene Islands, Indian Ocean).
In Feb. 1989, a field survey was conducted on Réunion to identify and assess the impact of introduced plant species that had become established in the remnants of native vegetation. The most successful invasion was of sites disturbed by human activities. However, alien plants were also found in primary forest, with at least 62 species penetrating into areas subjected to min. disturbance. Nevertheless, the forest remnants were still mainly dominated by indigenous or endemic plant species and maintained what was presumed to be their original vegetational structure. The most threatening plant invaders were the trees Psidium cattleyanum and Ligustrum robustum, the bramble Rubus alceifolius, the shrubs Fuchsia magellanica and Lantana camara, and the herbaceous species Hedychium gardnerianum, Boehmeria macrophylla and B. penduliflora. The early stages of primary succession on young volcanic sites were dominated by aggressively expanding populations of alien species. It appeared very unlikely that native species would replace invaders as the succession proceeds. It was concluded that the survival of many indigenous plant species in Réunion probably hinges on the active control of alien species.