Island biogeography of native and alien plant species: Contrasting drivers of diversity across the Lesser Antilles

Abstract

AbstractAimUnderstanding the factors driving the diversity of alien and native species on islands is crucial for predicting the spread of alien species and for proposing management practices to protect the unique native biodiversity that often occurs in insular ecosystems. The main objective of this study was to evaluate whether native and alien plant species respond similarly to natural biogeographic and human‐related drivers.LocationLesser Antilles, Caribbean.MethodsWe compiled a dataset with the verified status of native and alien plant species occurring on 15 islands across the Lesser Antilles. We assessed the relationship of native and alien plant species richness and identified the biogeographic and socio‐economic variables that best explain the diversity patterns of both alien and native species on these islands by combining correlation analysis and generalized linear models.ResultsThe final dataset comprises a total of 2,438 plant species with 1,825 native species and 613 alien species. For the 15 islands analysed, native and alien species richness is strongly and positively correlated, but different variables explained their diversity patterns. We found that biogeographic drivers such as island area, elevation and distance to the mainland best explain patterns of native species richness. On the other hand, alien species richness was well predicted by a combination of geographic and socio‐economic variables, with per capita gross domestic product (GDP) and island area having the strongest effect. Species composition of alien floras is also significantly influenced by the historical colonial identity of these islands.Main conclusionsWhile native species are clearly associated with biogeographic variables, alien species are strongly influenced by variables related to human activities and therefore anthropogenic disturbance processes. Modification of natural areas by human activities can result in high alien species richness even on islands with high native species richness.