UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Islands have been shown to be highly vulnerable to the invasion of non-native plant species. The island of Moorea, French Polynesia, is both geographically isolated and lacks a high diversity of native plant species, factors that promote the invasion of non-native plants. Disturbed areas, such as roadsides, have also been closely associated with the colonization and spread of non-native and invasive plants. Roads are particularly important vectors of alien plant invasions, aiding in dispersal and likely serving as starting points for edge effects. The present study considers both the alien and native flora in tropical secondary forests adjacent to paved vehicle roads, dirt vehicle roads, and backcountry hiking trails on Moorea, French Polynesia. The composition of total and alien plant species, level of invasion, and significance of edge effects were analyzed between the three corridor types. Significant differences in the alien plant compositions and level of invasion were found between the corridor types. Dirt roads were found to be the most invaded, followed by paved roads and then hiking trails. Two plant species, W. trilobata and A. falcatoria, showed dramatic edge effects into the adjacent forest; however, only the spread of W. trilobata was significantly affected by corridor type, with paved roads showing the greatest effect.