Exotic species invasion into Mauritius wet forest remnants

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Abstract
Two stands of mature evergreen wet forest in Mauritius (Mascarene Islands) were sampled for floristic composition to assess the extent of invasion by weedy exotic phanerogams (Brise Fer, 550 m alt.; Bon Courage, 200–260 m alt.). All individuals ≥ 2.5 cm dbh were recor ded in 50×2 m transects totalling 0.1 ha at each site, and 2×2 m seedling plots totalling 40 m were also sampled at each site. Both forests showed a high degree of invasion. Although exotics constituted only 5% of woody species ≥ 2.5 cm dbh at Brise Fer and 14.5% at Bon Courage, they comprised 34.8% and 20.8% of the individuals, respectively. Seedling plots at both sites were dominated by exotics, which comprised 20.6% of the species and 97.4% of the individuals at Brise Fer, and 22.2% of the species and 73.9% of the individuals at Bon Courage. Comparisons are made with Macabé forest, sampled nearly 50 years ago. These data suggest that unless steps are taken to check the spread of exotics, floristic composition at these sites will shift towards total invasion and degradation as has occurred elsewhere on Mauritius.