Data from: The timing of frugivore-mediated seed dispersal effectiveness

The seed dispersal effectiveness framework allows assessing mutualistic services from frugivorous animals in terms of quantity and quality. Quantity accounts for the number of seeds dispersed and quality for the probability of recruitment of dispersed seeds. Research on this topic has largely focused on the spatial patterns of seed deposition because seed fates often vary between microhabitats due to differences in biotic and abiotic factors. However, the temporal dimension has remained completely overlooked despite these factors – and even local disperser assemblages – can change dramatically during long fruiting periods. Here, we test timing effects on seed dispersal effectiveness, using as study case a keystone shrub species dispersed by frugivorous birds and with a fruiting period of nine months. We evaluated quantity and quality in different microhabitats of a Mediterranean forest and different periods of the fruiting phenophase. We identified the bird species responsible for seed deposition through DNA barcoding and evaluated the probability of seedling recruitment through a series of field experiments on sequential demographic processes. We found that timing matters: the disperser assemblage was temporally structured, seed viability decreased markedly during the plant’s fruiting phenophase, and germination was lower for viable seeds dispersed in the fruiting peak. We show how small contributions to seed deposition by transient migratory species can result in a relevant effectiveness if they disperse seeds in a high-quality period for seedling recruitment. This study expands our understanding of seed dispersal effectiveness, highlighting the importance of timing and infrequent interactions for population and community dynamics.

种子传播有效性（seed dispersal effectiveness）框架可用于评估食果动物提供的互利共生服务，评估维度分为数量与质量两类。其中，数量指代被传播种子的总数量，质量则指代被传播种子成功定植的概率。当前该领域的研究大多聚焦于种子沉积的空间格局，因为生物与非生物因素的差异会导致不同微生境下种子的命运存在显著区别。然而，尽管这些影响因素——乃至局域的传播者类群——在漫长的结果期内可能发生剧烈变化，时间维度却完全被忽视了。本研究以一种由食果鸟类传播、结果期长达九个月的关键灌木物种为研究对象，探究时间因素对种子传播有效性的影响。我们评估了地中海森林不同微生境以及果实物候期不同阶段下的传播数量与质量。通过DNA条形码（DNA barcoding）技术鉴定负责种子沉积的鸟类物种，并通过一系列针对连续种群统计过程的野外实验，评估幼苗定植的概率。研究结果表明时间维度至关重要：传播者类群具有时间结构特征；在植物结果物候期内，种子活力显著下降；且在结果高峰期传播的活力种子，其萌发率更低。本研究显示，若暂居性迁徙物种在对幼苗定植而言的高质量传播时期散播种子，即便其对种子沉积的贡献较小，也能产生可观的传播有效性。本研究拓展了我们对种子传播有效性的认知，强调了时间维度与非频繁互作对种群及群落动态的重要性。