Data from: Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands

When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence–absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore–fruit interactions.当功能群（guild）内的物种承担相似生态功能时，功能冗余（functional redundancy）可帮助生态系统抵御物种丢失带来的冲击。本研究基于鱼类与果实间的互作频率数据，对三处物种丰富的新热带湿地展开分析，探究共存食果动物（frugivore）是否能够提供冗余的种子传播（seed dispersal）服务。研究结果显示，食果鱼类的食性较为泛化；但体型较大的鱼类相比小型鱼类，拥有更广的种子传播广度，在部分情况下可提供小型鱼类无法实现的种子传播服务。由于过度捕捞（overfishing）对大型鱼类的影响更为显著，相较于小型专食性食果动物的消失，这类大型鱼类的局部灭绝可能会引发更为严重的植物次生灭绝事件。为评估食果动物特化对互作网络稳定性的影响，我们从不同生态系统的39篇已发表文献中提取了食果鸟类、哺乳类及鱼类的种子传播互作网络（本研究网络）数据。针对互作频率的分析结果显示，相较于基于二元数据（即互作有无）的分析，本研究中食果动物的特化程度更低，且互作网络的嵌套性（nestedness）也更弱。在此情形下，生态系统对任意单一食果动物的丢失可能具备恢复力。然而，食果动物灭绝的网络鲁棒性会随特化程度升高而下降，因此以专食性食果动物为主的互作网络，对泛化物种的丢失极为敏感。与二元数据的分析方法不同，近年开发的可用于建模互作强度的算法，通过纳入食果动物-果实互作的异质性，为我们深化对复杂生态网络的认知提供了可能。