Data from: Toucans (Ramphastos ambiguus) facilitate resilience against seed dispersal limitation to a large-seeded tree (Virola surinamensis) in a human-modified landscape

Large-seeded plants may suffer seed dispersal limitation in human-modified landscapes if seed dispersers are absent or unable to disperse their seeds. We investigated dispersal limitation for the large-seeded tree Virola surinamensis in a human-modified landscape in southern Costa Rica. During two fruiting seasons, we monitored crop size, seed removal rates, the number of fruiting conspecifics within 100 m, and feeding visitation rates by frugivores at trees located in high and low forest disturbance conditions. Seed removal rates and the total number of seeds removed were high regardless of the disturbance level, but these parameters increased with tree crop size and decreased with the number of fruiting V. surinamensis trees within a 100 m radius. Trees at low disturbance levels were more likely to be visited by seed dispersers. Black mandibled toucans (Ramphastos ambiguus) and spider monkeys (Ateles geoffroyi) were the most important seed dispersers, based on visitation patterns and seed removal rates. Spider monkey feeding visits were more frequent at high disturbance levels, but the monkeys preferentially visited isolated trees with large yields and surrounded by a low number of fruiting Virola trees within 100 m. Toucan visitation patterns were not constrained by any of the predictors and they visited trees equally across the landscape. We suggest that isolated and highly fecund Virola trees are an important food resource for spider monkeys in human-modified landscapes and that toucans can provide resilience against seed dispersal limitations for large-seeded plants in human-modified landscapes in the absence of hunting.

在人为干扰景观中，若种子传播者缺失或无法完成种子传播，大种子植物可能面临种子传播限制问题。本研究在哥斯达黎加南部的人为改造景观中，针对大种子植物苏里南油桃木（Virola surinamensis）开展了种子传播限制相关调查。在两个果期内，我们对位于森林高、低干扰条件下的苏里南油桃木个体进行监测，记录其挂果量、种子移除率、100米范围内结果同种个体数量，以及食果动物的取食访问频率。结果显示，无论干扰水平高低，种子移除率及总移除种子量均处于较高水平；但上述参数随单株挂果量上升而升高，随100米半径内结果苏里南油桃木个体数量增加而降低。低干扰区域的树木更易被种子传播者访问。基于访问模式与种子移除率分析，黑嘴巨嘴鸟（Ramphastos ambiguus）和 Geoffroy蜘蛛猴（Ateles geoffroyi）是该区域最为关键的种子传播者。Geoffroy蜘蛛猴的取食访问在高干扰区域更为频繁，但它们优先选择100米范围内结果同种个体较少、挂果量大的孤立个体。巨嘴鸟的访问模式不受上述任一预测因子的限制，其在研究区域内的树木间访问频率均匀一致。我们认为，在人为干扰景观中，孤立且挂果量大的苏里南油桃木个体是蜘蛛猴的重要食物资源；而在未受狩猎干扰的情况下，巨嘴鸟可帮助大种子植物缓解人为干扰景观中的种子传播限制问题，提升其种群恢复力。