Seed dispersal by animals is a complex phenomenon, characterized by multiple mechanisms and variable outcomes. Most researchers approach this complexity by analysing context‐dependency in seed dispersal and investigating extrinsic factors that might influence interactions between plants and seed dispersers. Intrinsic traits of seed dispersers provide an alternative way of making sense of the enormous variation in seed fates. I review causes of intraspecific variability in frugivorous and granivorous animals, discuss their effects on seed dispersal, and outline likely consequences for plant populations and communities. Sources of individual variation in seed‐dispersing animals include sexual dimorphism, changes associated with growth and ageing, individual specialization, and animal personalities. Sexual dimorphism of seed‐dispersing animals influences seed fate through diverse mechanisms that range from effects caused by sex‐specific differences in body size, to influences of male versus female cognitive functions. These differences affect the type of seed treatment (e.g. dispersal versus predation), the number of dispersed seeds, distance of seed dispersal, and likelihood that seeds are left in favourable sites for seeds or seedlings. The best‐documented consequences of individual differences associated with growth and ageing involve quantity of dispersed seeds and the quality of seed treatment in the mouth and gut. Individual specialization on different resources affects the number of dispersed plant species, and therefore the connectivity and architecture of seed‐dispersal networks. Animal personalities might play an important role in shaping interactions between plants and dispersers of their seeds, yet their potential in this regard remains overlooked. In general, intraspecific variation in seed‐dispersing animals often influences plants through effects of these individual differences on the movement ecology of the dispersers. Two conditions are necessary for individual variation to exert a strong influence on seed dispersal. First, the individual differences in traits should translate into differences in crucial characteristics of seed dispersal. Second, individual variation is more likely to be important when the proportions of particular types of individuals fluctuate strongly in a population or vary across space; when proportions are static, it is less likely that intraspecific differences will be responsible for changes in the dynamics and outcomes of plant–animal interactions. In conclusion, focusing on variation among foraging animals rather than on species averages might bring new, mechanistic insights to the phenomenon of seed dispersal. While this shift in perspective is unlikely to replace the traditional approach (based on the assumption that all important variation occurs among species), it provides a complementary alternative to decipher the enormous variation observed in animal‐mediated seed dispersal.

中文翻译：

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种子传播动物的种内变异对植物有何影响

动物传播种子是一种复杂的现象，具有多种机制和可变结果。大多数研究人员通过分析种子传播的环境依赖性和调查可能影响植物和种子传播者之间相互作用的外在因素来解决这种复杂性。种子传播者的内在特征提供了另一种理解种子命运巨大变化的方法。我回顾了食果类和食谷类动物种内变异的原因，讨论了它们对种子传播的影响，并概述了对植物种群和群落可能产生的影响。种子传播动物个体变异的来源包括性别二态性、与生长和衰老相关的变化、个体特化和动物个性。种子传播动物的性别二态性通过多种机制影响种子命运，这些机制的范围从由性别特异性体型差异引起的影响，到男性与女性认知功能的影响。这些差异影响种子处理的类型（例如散布与捕食）、散布种子的数量、种子散布的距离以及种子留在种子或幼苗的有利地点的可能性。与生长和衰老相关的个体差异的最佳记录结果涉及分散种子的数量以及口腔和肠道中种子处理的质量。对不同资源的个体专业化会影响分散植物物种的数量，从而影响种子传播网络的连通性和结构。动物个性可能在塑造植物与其种子传播者之间的相互作用方面发挥重要作用，但它们在这方面的潜力仍然被忽视。一般来说，种子传播动物的种内变异通常通过这些个体差异对传播者运动生态学的影响来影响植物。个体变异对种子传播产生强烈影响需要两个条件。首先，性状的个体差异应转化为种子传播关键特征的差异。其次，当特定类型个体的比例在群体中剧烈波动或跨空间变化时，个体差异可能更重要；当比例是静态的时，种内差异不太可能导致动植物相互作用的动力学和结果的变化。总之，关注觅食动物之间的差异而不是物种平均值可能会为种子传播现象带来新的、机械的见解。虽然这种观点转变不太可能取代传统方法（基于所有重要变异都发生在物种之间的假设），但它提供了一种补充替代方法来破译在动物介导的种子传播中观察到的巨大变异。