Invasional meltdown potential: Facilitation between introduced plants and mammals on French Mediterranean islands

:In the increasingly important domain of insular invasion ecology, the role of facilitation between different introduced taxa has been mentioned, but rarely studied. This paper outlines facilitation between introduced mammals and the invasive succulents Carpobrotus edulis and C.aff. acinaciformis on offshore islands in southeast France. Rats and rabbits are the primary seed dispersers of Carpobrotus sp. on the islands studied. No such dispersal activity was detected on the adjacent mainland. Seed digestion by rats and rabbits also enhanced percent seed germination and speed, in spite of an associated reduction in seed size. In return, Carpobrotus provides a water/energy-rich food source during the dry summer season, thus demonstrating a clear case of mutualism between invaders.