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Data from: From species lists to interactions: Network structure, not richness, guides seed dispersal management in human-modified islands

Costa, Alba123; Nogales, Manuel4; Traveset, Anna1; Kaiser-Bunbury, Christopher N.5; Zora, Anna6; Berke, Gregory7; Hervías-Parejo, Sandra18

Published Apr 23, 2026 on Dryad. https://doi.org/10.5061/dryad.v15dv42bq

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Abstract

Seed dispersal by animals supports plant regeneration and ecosystem resilience, yet conservation success is still commonly evaluated using species richness rather than the organisation of ecological interactions. This is particularly problematic in human-modified ecosystems, where management interventions can increase diversity without restoring historical interaction structures or functional stability. We compared seed dispersal networks on two climatically and biogeographically similar oceanic islands in the Seychelles archipelago with contrasting management trajectories: one strictly protected and under historically oriented management, aimed at limiting introductions and maintaining historically informed community structure, and one anthropogenically diversified through long-term human occupation and species introductions. Using a multi-metric ecological network approach integrating modularity-based roles, centrality indices and motif analyses, we quantified how plants and dispersers contribute to network structure under each management context. Anthropogenic diversification increased interaction diversity and the number of dispersal events but resulted in a less cohesive network dominated by peripheral species and a narrow set of structurally central dispersers. In contrast, the historically oriented management island exhibited lower interaction diversity but greater network cohesion, with strong redundancy in plant-level dispersal pathways. Shared species occupied different structural roles across islands, indicating strong context dependence in their contribution to seed dispersal networks. Motif analyses revealed contrasting interaction niche structures across management contexts. In the anthropogenically diversified island, dispersal relied on a small set of generalist dispersers, suggesting potential vulnerability to their loss. In the historically oriented management island, dispersal was spread across more species, indicating greater redundancy. These differences imply distinct but predictable vulnerabilities arising from alternative management pathways. Our findings show that management strategies can create fundamentally different seed dispersal regimes, even under similar environmental conditions. Anthropogenic diversification reshapes network organisation into distinct structural configurations, rather than consistently enhancing overall cohesion. Incorporating interaction structure into conservation planning can help prioritise key dispersers and plants, anticipate hidden vulnerabilities, and guide management actions that better sustain seed dispersal processes in human-modified island ecosystems.