Data from: Local extinctions of obligate frugivores and patch size reduction disrupt the structure of seed dispersal networks

A central problem in ecology is to understand how human impacts affect plant-animal interactions that lead to effective seed dispersal services for plant communities. Seed dispersal services are the outcome of plant-frugivore interactions that often form local networks of interacting species. Recent work has shown that some frugivorous bird species are more critical to network organization than others. Here, we explore how patch size and the potential local extinctions of obligate frugivorous birds affect the reorganization of seed dispersal networks. We examined the structure of 20 empirical seed dispersal networks documented across tropical avian assemblages occupying widely variable habitat patch sizes, a surrogate of the amount of remaining habitat. Networks within small forest patches consistently supported both lower plant and bird species richness. Forest patch size was positively associated with nestedness, indicating that reductions in patch size disrupted the nested organization of seed dispersal networks. Obligate frugivores, especially large-bodied species, were almost entirely absent from small forest patches. Analysis at the species level showed that obligate frugivores formed the core of interacting species, connecting species within a given seed dispersal network. Our combined results revealed that patch size reduction erodes frugivorous bird diversity, thereby affecting the integrity of seed dispersal networks. We highlight the importance of conserving large forest patches to maintain tropical forest functionality.生态学的核心议题之一，在于解析人类活动干扰如何影响动植物间的互作关系，进而为植物群落维系有效的种子传播服务。种子传播服务是植物-食果动物互作（plant-frugivore interaction）的产物，这类互作通常会形成互作物种的局域网络。已有研究表明，部分食果鸟类（frugivorous bird）对种子传播网络（seed dispersal network）结构的维系作用相较于其他物种更为关键。本研究旨在探讨生境斑块面积以及专性食果鸟类（obligate frugivorous bird）的潜在局域灭绝，会如何影响种子传播网络的重组。我们对20个源自热带鸟类群落的实证种子传播网络展开分析，这些群落栖息于生境斑块面积差异悬殊的区域，而斑块面积可作为剩余生境总量的替代指标。小型林斑中的种子传播网络，其承载的植物与鸟类物种丰富度均显著更低。森林斑块面积与嵌套性（nestedness）呈正相关，这表明斑块面积缩减会破坏种子传播网络的嵌套组织结构。专性食果鸟类，尤其是体型较大的类群，几乎完全不见于小型林斑。物种水平的分析显示，专性食果鸟类构成了互作物种的核心类群，连接着给定种子传播网络内的各个物种。综合本研究的结果可见，斑块面积缩减会削弱食果鸟类的多样性，进而损害种子传播网络的完整性。本研究强调，保护大型森林斑块对于维持热带森林的生态功能具有重要意义。