Are birds, wind and gravity legitimate dispersers of fleshy-fruited invasive plants on Robinson Crusoe Island, Chile?

• Austral thrush is a legitimate disperser of three invasive plant species on Robinson Crusoe Island.
• Wind and gravity are also legitimate seed dispersers of two invasive fleshy-fruited species.
• Forest invasive plants have more seedling emergence in canopy gaps than in closed forest.

Although fleshy-fruited species are usually dispersed by animals and gravity, previous research shows that the fleshy fruits of invasive plants on Robinson Crusoe Island (RC) are also moved by wind. To determine whether a bird (Turdus falcklandii), wind, and gravity could be legitimate dispersers of fleshy fruits from the invasive plant species Aristotelia chilensis, Rubus ulmifolius and Ugni molinae, we carried out germination trials with seeds defecated by T. falcklandii and hand-cleaned in the laboratory, and added another trial in field conditions, sowing intact fruits. Whole fruits sown intact are used to represent dispersal by wind or gravity. The field trials for A. chilensis and R. ulmifolius were performed in canopy gaps and closed forests to evaluate the effect of shadow on seedling emergence. Field trials for U. molinae were only established in open shrubland, since this species does not occur in forests on RC. Laboratory trials showed gut-passed A. chilensis seeds increased the germination percentage while gut-passed seeds did not affect germination in R. ulmifolius and U. molinae. In the field, trials revealed that seeds from intact fruits germinated in a similar way to gut-passed or hand-cleaned seeds, with the exception of U. molinae, which did not germinate inside fruits. In all field treatments, the germination percentage of A. chilensis and R. ulmifolius was higher in the canopy gaps than under closed canopy. These results indicate that T. falcklandii is a legitimate disperser for the three invasive species studied on RC. Wind and gravity should also be considered legitimate dispersers of A. chilensis and R. ulmifolius. Microhabitat (i.e., canopy gaps) plays a more important role in improving the establishment of A. chilensis and R. ulmifolius than the dispersal mechanism itself.