In flowering communities, plant species commonly share pollinators and therefore plant individuals receive heterospecific pollen (HP). However, the patterns of HP transfers can deviate from patterns of plant-pollinator visitations. Although flower-visitor interactions are known to be mediated by floral traits, e.g. floral size or nectar tube depth, the explanatory power of these traits for HP transfer patterns remains elusive. Here, we have explored pollen transfer patterns at three sites in Southern Germany on three dates (early, mid and late summer). At the plant level, we tested whether flower abundance and floral traits are correlated with HP reception and donation. At the community level, we determined whether flower and bee diversity are correlated with network modularity and whether floral traits explain the module affiliation of plant species. We collected the stigmas of flowering plant species, analysed HP and conspecific pollen (CP) loads and measured floral traits, flower and bee diversity. Our results show that the degree and intensity of HP reception or donation at the plant level do not correlate with floral traits, whereas at the community level, the module affiliation of who is sharing pollen with whom is well-explained by floral traits. Additionally, variation in network modularity between communities is better explained by plant diversity and abundance than by bee diversity and abundance. Overall, our results indicate that floral traits that are known to mediate flower-visitor interactions can improve our understanding of qualitative HP transfer but only provide limited information about the quantity of HP transfer, which more probably depends on other floral traits, flower-visitor identity or community properties.

中文翻译：

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花性状与异质性花粉负载的质量有关，而与数量无关

在开花社区中，植物物种通常共享传粉媒介，因此植物个体会接受异种花粉（HP）。但是，HP转移的模式可能与植物授粉媒介访视的模式不同。尽管已知花-访花者之间的相互作用是由花性状（例如花大小或花蜜管深度）介导的，但这些性状对于HP转移模式的解释能力仍然难以捉摸。在这里，我们在三个日期（夏初，夏中和夏末）探索了德国南部三个地点的花粉转移方式。在植物级别，我们测试了花的丰度和花性状是否与HP的接受和捐赠相关。在社区一级，我们确定了花和蜂的多样性是否与网络模块性相关，以及花性状是否解释了植物物种的模块隶属关系。我们收集了开花植物物种的柱头，分析了HP和特定花粉（CP）的负载，并测量了花卉性状，花和蜂的多样性。我们的结果表明，在植物水平上HP接受或捐赠的程度和强度与花卉性状不相关，而在社区水平上，谁与谁共享花粉的模块隶属关系可以通过花卉性状得到很好的解释。此外，通过植物多样性和丰度比通过蜜蜂多样性和丰度更好地解释了社区之间网络模块化的变化。总体，