Dynamique des populations de l'arbre endémique Myrsine longifolia (Myrsinacées) dans les forêts de Tahiti (Polynésie Française) envahies par Miconia calvescens (Mélastomatacé es) après introduction d'un champignon pathogène de lutte biologique : Premières investigations
The invasion of the native wet forests of the tropical oceanic island of Tahiti (French Polynesia, South Pacific) by miconia, Miconia calvescens DC. (Melastomataceae), a tree introduced as an ornamental plant in 1937, has caused the decline of many endemic plant species following the drastic decrease of the light in the understory. Among them, the small dioiceous tree Myrsine longifolia Nadeaud (Myrsinaceae) which is considered as critically endangered (CR) by IUCN and is legally protected in French Polynesia. Because of the importance of the invaded areas and the steep relief of Tahiti, biological control is the only option that could reduce the impacts of this invasive alien plant, and contribute to the recovery of endangered endemic plants. A fungal pathogen, highly specific to miconia, Colletotrichum gloeosporioides forma specialis miconiae (Deuteromycotina), was successfully introduced to Tahiti in 2000. It has spread all over the island in a few years, infecting nearly all the miconia plants between 10 and 1400 m elevation, and has caused the partial defoliation of the miconia trees in the canopy. This study is an attempt to demonstrate both: (1) the impact of miconia invasion on the population structure of Myrsine longifolia which is characterized by rare isolated reproductive trees (> 2-10 m in height), a small number of individuals of intermediate height and diameter classes (between 20 cm and 2 m), and a decrease of the number of seedlings (< 20 cm) with an increasing level of miconia invasion; (2) an increasing seedling recruitment of Myrsine longifolia in highly invaded miconia forests where attack of the fungal pathogen on miconia leaves has caused higher defoliation in the canopy. The biocontrol agent introduced to control the invasive plant miconia in Tahiti has allowed the regeneration and recovery of an endemic endangered plant species.
- ISSN: 0249-7395