Data from: Beyond pollen:ovule ratios: Evolutionary consequences of pollinator dependence and pollination efficiency for pollen and ovule production in angiosperms

Premise: The relative per‐flower production of ovules and pollen varies
broadly with angiosperm mating systems, with outcrossing types commonly
producing more pollen grains per ovule than selfing types. The
evolutionary causes of this variation are contentious, especially the
relevance of pollination risk. Resolution of this debate may have been
hampered by its focus on pollen:ovule (P:O) ratios rather than on the
evolution of pollen and ovule numbers per se. Methods: Using published
mean ovule and pollen counts, we analyzed associations with the proportion
of removed pollen that reaches stigmas (pollen‐transfer efficiency) and
differences between pollinator‐dependent and autogamous forms within and
among species. Analyses involved Bayesian methods that simultaneously
considered variation in pollen and ovule numbers and accounted for
phylogenetic relatedness. We also assessed the utility of P:O ratios as
mating‐system proxies and their association with female outcrossing rates.
Results: Median pollen number declined consistently with
pollen‐transfer efficiency among species, whereas median ovule number did
not. Similarly, in both intraspecific and interspecific analyses,
pollinator‐dependent plants produced more pollen than autogamous plants,
whereas ovule production did not differ statistically. Distributions of
P:O ratios overlapped extensively for self‐incompatible and
self‐compatible species and for different mating‐system classes, and P:O
ratios correlated weakly with outcrossing rate. Conclusions: Our findings
demonstrate that pollinator dependence and pollination efficiency commonly
influence the evolution of pollen number per flower but have more limited
effects on ovule number. P:O ratios provide ambiguous, possibly
misleading, information about mating systems, especially when compared
among clades.

前提：被子植物（angiosperm）交配系统中，每朵花的胚珠与花粉相对产量存在显著差异——异交（outcrossing）类型通常每胚珠产生的花粉粒数量多于自交（selfing）类型。这种变异的进化原因存在争议，尤其是传粉风险的相关性。该争议未能得到解决，可能是因为研究聚焦于花粉-胚珠比（pollen:ovule, P:O ratio）而非花粉与胚珠数量本身的进化。方法：利用已发表的平均胚珠与花粉计数数据，我们分析了以下关联：移除花粉中到达柱头的比例（传粉效率，pollen-transfer efficiency），以及传粉者依赖型与自花受精型（autogamous）植物在种内和种间的差异。分析采用贝叶斯方法，同时考虑花粉与胚珠数量的变异，并纳入系统发育相关性（phylogenetic relatedness）。我们还评估了P:O比作为交配系统代理指标的效用，及其与雌性异交率的关联。结果：种间分析显示，随着传粉效率的提高，花粉数量中位数呈一致性下降，而胚珠数量中位数无此趋势。同样，在种内和种间分析中，传粉者依赖型植物产生的花粉量显著多于自花受精型植物，但两者的胚珠产量无统计学差异。自交不亲和（self-incompatible）物种与自交亲和（self-compatible）物种、不同交配系统类别的P:O比分布存在广泛重叠，且P:O比与异交率的相关性较弱。结论：本研究结果表明，传粉者依赖性与传粉效率通常影响每朵花花粉数量的进化，但对胚珠数量的影响有限。P:O比提供的交配系统信息模糊，甚至可能具有误导性，尤其是在分支间比较时。