Summary Pollination presents a risky journey for pollen grains. Pollen loss is sometimes thought to favour greater pollen investment to compensate for the inefficiency of transport. Sex allocation theory, to the contrary, has consistently concluded that postdispersal loss should have no selective effect on investment in either sex function. But the intuitively appealing compensation idea continues to be raised despite the lack of theoretical endorsement. We address the theoretical issue with a model that directly represents pollen loss (and ovule loss through floral demise or loss of receptivity) as rate‐dependent dynamical processes. These loss rates can be varied to examine the effect of pollination efficiency on optimal sex allocation. Pollen–ovule ratios follow from the sex allocation based on the resource costs of pollen and ovule production. This model confirms conventional findings that pollen loss should have essentially no effect on sexual resource allocation in large, panmictic populations. Pollen limitation of seed set does not alter this conclusion. These results force us to rethink the empirical association of pollination efficiency with low pollen–ovule ratios. This pattern could arise if efficient pollen transport commonly results in stigmatic deposition of cohorts of related pollen. Empirical evidence of correlated paternity supports this explanation.

中文翻译：

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授粉效率和花粉胚珠比


摘要 授粉对花粉粒来说是一个危险的旅程。有时认为花粉损失有利于更多的花粉投入，以弥补运输效率低下的情况。相反，性别分配理论一致得出这样的结论：分散后的损失不应对任一性别功能的投资产生选择性影响。但尽管缺乏理论支持，直观上有吸引力的补偿想法仍在继续被提出。我们用一个模型来解决这个理论问题，该模型直接将花粉损失（以及通过花死亡或接受性损失而导致的胚珠损失）表示为速率依赖的动态过程。可以改变这些损失率来检查授粉效率对最佳性别分配的影响。花粉-胚珠比率是根据花粉和胚珠生产的资源成本的性别分配得出的。该模型证实了传统的发现，即花粉损失对大规模恐慌人群的性资源分配基本上没有影响。种子集花粉的限制不会改变这一结论。这些结果迫使我们重新思考授粉效率与低花粉胚珠比率的经验关联。如果有效的花粉运输通常导致相关花粉群的柱头沉积，则可能会出现这种模式。相关亲子关系的经验证据支持了这一解释。