Frugivore loss may lead to seed dispersal disruption, but this issue has rarely been addressed in the context of tropical primary succession where seed dispersal is a critical step in plant recolonisation. Recent works in several tropical forests suggest that native tree diversity and dynamics are negatively impacted by the disruption of plant-frugivore interactions as a consequence of defaunation. Different limiting factors, i.e. seed predation and competition with dense low vegetation, probably act in synergy with defaunation and must be disentangled to understand biodiversity loss processes. We set up a field experiment on Reunion where most large frugivores went extinct in 1800 and where the Piton de la Fournaise provides a natural experimental design: a historical lava flow bordered on both sides by an old-growth forest. We address the following questions: (1) Is the absence or rarity of native fleshy-fruited (FF) species on the historical lava flow explained by seed dispersal disruption? (2) Are large-seeded FF plants able to grow up once experimentally dispersed from old-growth forest seed sources? We monitored the active seed rain on the historical lava flow in a landscape with a high adult-plant diversity and the growth of four large-seeded trees in a manipulative factorial experiment (seed predator exclosure and fern uprooting) on the historical lava flow where these trees were totally absent. Preliminary results show that the active seed rain was dominated by native anemochorous and alien FF plants; large-seeded FF plants were absent from the seed rain despite a nearby large availability of diaspores; large-seeded trees were able to establish on lava flows, whatever the treatment. The absence of native large-seeded trees and the high abundance of alien small-fleshy-fruited plants in the monitored seed rain demonstrates that present plant-frugivore interactions are diverted for the benefit of non-native invasive plants. The ability of large-seeded plants to establish on the historical lava flow show that dispersal disruption, more than environmental filtering or predation effects, explains the complete absence of these species. Our study emphasizes the fundamental role of seed dispersal loss in ecosystem stable-state shifts and the urgency to restore it through large frugivores rewilding actions.