Changes in lowland dry-forest native and alien plant communities on Réunion Island (Indian Ocean) over 16 years

Abstract

Native floras of oceanic islands are among the most threatened on Earth. For example, only 1% of intact dry-forest ecosystems remain on Réunion, harbouring numerous endangered native species. Alien species invasion is one of the more important threats facing these ecosystems, as it has been hypothesized that, over time, the abundance of alien species will increase more than that of native species. To explore this, we studied floristic changes over a 16 year period (1995–2011) in six dry-forest remnants. Species richness and abundance increased for both alien and native species over this period, but at a significantly higher rate for the abundance of invasive alien plants. Despite this, Jaccard’s coefficient indicates a high level of similarity between the communities of 1995 and 2011. Also, the single site that benefited from invasive species management experienced the largest increase in native species, both in terms of specific richness and abundance. This study underlines the importance of permanent plots in studying the dynamics of invaded communities and in understanding plant succession. It also suggests a potential temporal persistence of island dry-forest communities, despite the expansion of alien species, and suggests the development of a new pathway in secondary succession where native and alien species coexist.