Data from: Bees learn preferences for plant species that offer only pollen as a reward

The astonishing diversity of floral form in angiosperm plants is driven in large part by preferences of pollinators for various floral traits, including learned preferences. Remarkably, almost all of a vast literature on learning and memory in pollinators relates to nectar as a reward, even though bees and many flies, beetles, and butterflies must collect pollen. In this study, we asked if bees formed preferences for plant species from which pollen had been collected successfully. Using absolute conditioning, we gave pollen foraging bees experience with plant species that offered only pollen rewards. Naive bees generally showed modest preferences, whereas experienced bees adopted strong preferences for those species over alternative species not previously experienced. Learned preferences were retained for at least 24h, consistent with preferences learned with nectar rewards. These experience-mediated changes in preference raised the possibility that bees formed associations between particular floral features and pollen rewards. We therefore asked if learned preferences required that bees successfully collect pollen. Using differential conditioning, we determined that learned preferences were strongly influenced by receipt of a pollen reward. In a final experiment, we characterized the importance of 2 floral features, the corolla and the anther, in the expression of learned preferences. Although experience altered responses to both floral parts, responses to anthers were influenced more strongly. We discuss recent evidence in the literature for associative learning with pollen rewards and propose that learned preferences in the context of pollen collection have played an important role in floral display evolution.

被子植物（angiosperm）花部形态的惊人多样性，在很大程度上由传粉者（pollinator）对各类花部性状的偏好所驱动，其中包括后天习得的偏好。值得关注的是，尽管蜂类、多数蝇类、甲虫与蝴蝶均需采集花粉，但现有关于传粉者学习与记忆的海量研究中，几乎全部都仅以花蜜作为奖赏展开探讨。本研究旨在探究蜂类是否会对成功采集过花粉的植物物种形成偏好。我们采用绝对条件化（absolute conditioning）训练，让正在进行花粉采集的蜂类接触仅提供花粉奖赏的植物物种。未接受过相关训练的蜂类通常仅表现出微弱的偏好，而经历过训练的蜂类则会对该物种产生显著强于未接触过的替代物种的偏好。习得的偏好至少可保留24小时，这与以花蜜为奖赏所习得的偏好特征一致。这类由经历介导的偏好改变，提示蜂类可能会在特定花部特征与花粉奖赏之间建立关联。为此我们进一步探究，习得偏好是否需要蜂类成功采集到花粉。通过差别条件化（differential conditioning）实验，我们证实习得偏好会显著受到花粉奖赏获取情况的影响。在最后一项实验中，我们针对花部的两个关键特征——花冠（corolla）与花药（anther）——在习得偏好表达中的重要性进行了表征。尽管经历会改变蜂类对这两种花部结构的反应，但对花药的反应受影响程度更强。我们讨论了当前文献中关于花粉奖赏关联学习的最新研究证据，并提出在花粉采集过程中形成的习得偏好，在花部形态演化中发挥了重要作用。