Exotic plant species can cause major damage to ecosystems that lack their natural predators and competitors. Several species produce fleshy fruits and are spread by frugivorous birds, replacing native fruit in their dispersers’ diets and forming mutualistic relationships with local frugivorous fauna. If fruit-feeders forage on multiple species then these plants may indirectly affect the dispersal of fellow fruit-producers through contagious dispersal, allowing facilitative relationships to form between various native and exotic plant species. This study aims to answer the question: How does the fruiting neighborhood surrounding a plant influence the seed rain beneath it? The study sites are located in the Grand Bay National Estuarine Research Reserve (GBNERR) in coastal Mississippi and in the Weeks Bay National Estuarine Research Reserve (WBNERR) in coastal Alabama. Seed traps were set up beneath individuals of two exotic (Cinnamomum camphora and Triadica sebifera) and three native (Morella cerifera, Ilex vomitoria, and Persea borbonia) winter fruiting species. The fruiting neighborhood surrounding each of these specimens was counted during setup and collections were taken monthly for the entirety of the fruiting season (2017-2018). The composition of each plant’s seed rain was compared to the composition of its fruiting neighborhood.
Results/Conclusions
Results indicate that these synchronously-fruiting plants are experiencing contagious dispersal. Specifically, the native species M. cerifera and I. vomitoria were found to positively affect dispersal of the invasive T. sebifera, which could be a key factor in its rapid proliferation throughout the Southeastern United States. M. cerifera and I. vomitoria, two of the most common shrub species in the region, may act as dispersal hubs for this exotic species, suggesting that these habitats are at great risk for continued invasion.