Landscape-scale forest cover shapes the complexity of seed-dispersal networks in regenerating forest fragments

Despite the recognition of animal-mediated seed dispersal as a critical driver of forest regeneration, little remains known on plant-frugivore interaction networks in secondary forest fragments. Such knowledge is especially relevant in fragmented landscapes where regenerating forest fragments lie scattered in a human-modified, agricultural matrix, such as in the Atlantic Forest region in Brazil. There, we investigated how habitat connectivity influences the complexity of plant-frugivore interaction networks across a chronosequence of eight secondary and two old-growth forest fragments. By employing camera traps and focal observations over two years, we documented over 10,000 plant-frugivore interactions. Our findings reveal that forest age does not significantly affect animal-mediated seed-dispersal networks; instead, landscape-scale forest cover drives network interaction quantity and structure. Even a modest 5 % increase in forest cover enhances the total number of interactions by as much as 22 %, demonstrating that small gains in connectivity can yield substantial ecological benefits. With increasing forest cover, networks become more modular and specialized, favouring rarer species' interactions and enhancing seed-dispersal functions. Across all fragments, birds with high occurrence and a high degree of frugivory played a crucial role in sustaining network structure and functionality. Together with late-successional plants, these bird species are instrumental in supporting regeneration within fragmented landscapes. The limited effect of mere forest age on network development suggests that passive regeneration may not suffice for isolated regenerating forest in landscapes with low forest cover, and that assisted regeneration—or active restoration—may be required to facilitate their network recovery.