Predicting the potential threat of Casuarina equisetifolia to three endemic plant species on the Turks and Caicos Islands

Abstract

Invasive species are one of the main threats to the loss of global biodiversity. Controlling such species requires a high input of effort and resources and therefore it is important to focus control on areas that will maximize gains for conservation. We present a spatial modelling approach that will help target control efforts. We used presence-only data to develop habitat suitability models for the invasive tree Casuarina equisetifolia and three endemic plant species on the Turks and Caicos Islands in the Caribbean. Substantial overlap was found between suitable areas for the endemics and C. equisetifolia. Evidence for the potential harm that C. equisetifolia could cause to native vegetation was assessed using paired areas with and without invasion. Areas with C. equisetifolia present had lower native plant species richness than areas where it was absent, which suggests a negative effect of invasion on the growth of native plants. No endemic plants were found in areas where C. equisetifolia was present. Based on the data collected we recommend that the three endemic species be categorized as Endangered on the IUCN Red List. By highlighting areas where the endemic plants are found and demonstrating a potential threat to these habitats, we provide a plan for the designation of six Important Plant Areas to promote conservation of these endemic species. © 2012 Fauna & Flora International.