Impacts of plant invasion on species diversity in Mediterranean islands

diversity, potential impact ABSTRACT: The relationship between plant invasion and the diversity of native plant communities was investigated in six Mediterranean islands and in different habitats. Species abundances were recorded in close-paired plots. One was a control and the other was invaded by one of these three target invaders: Ailanthus altissima, Oxalis pes-caprae or Carpobrotus spp. The diversity and the intensity of the change between the control and the invaded plot were calculated. The presence of Carpobrotus spp. was clearly associated with a decrease of diversity between the control and the invaded plots on the dune, on the rocky coast and in all the islands. The intensity of the change was similar whatever the island and the habitat. For Ailanthus altissima and Oxalis pes-caprae, differences of diversity between control and invaded plots occurred only in few islands and habitats. For Oxalis pes-caprae, the intensity of change of diversity was different between the islands and the habitats.