Saab Gabriella da Silva, Mansano Vidal de Freitas, Nogueira Anselmo, Maia Isabele Carvalho, Bergamo Pedro Joaquim, Paulino Juliana Villela
Departamento de Produtos Naturais e Alimentos, Faculdade de Farmácia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ 21941-902, Brazil.
Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, DIPEQ, Rua Pacheco Leão 915, Rio de Janeiro, RJ 22460-030, Brazil.
AoB Plants. 2021 Aug 27;13(5):plab054. doi: 10.1093/aobpla/plab054. eCollection 2021 Oct.
Buzz-pollinated pollen flowers have pollen as the primary resource for pollinators and must deal with a conflict between the exploitation of pollen grains by bees and pollination success. It has been hypothesized that heterostemony allows division of labour between stamens as a solution to the pollen dilemma. To test the division of labour hypothesis, we chose , which has a trimorphic androecium and analysed androecium development, pollen grain release mechanisms and visitor behaviour. We explored the reflectance of floral organs and carried out an exclusion experiment to test the attractiveness of each stamen morph to the bee species. Finally, we explored the structural, ultrastructural and functional variation between the pollen grains, including pollen viability across stamen morphs. The differences among the three stamen morphs, which is developed from two whorls of the stamen, are the first evidence of the division of labour in our study system. Large and bees actively and exclusively exploited the pollen grains from the central poricidal anthers generating pollen deposition on their bodies. The reflectance pattern of floral organs indicated a targeting of these large bees to the central anthers, corroborated by the anther manipulative experiment where only the exclusion of the anthers positioned in the flower centre, especially the intermediate stamens, reduced bee visits. Both results revealed a division of labour, in which the intermediate stamen morph was responsible for both floral attractiveness and pollen resources. Only the largest stamen morph produced germinable pollen grains, highlighting their role as pollinating stamens. The smallest stamen morph has a less clear function, likely representing an economy in pollen production for feeding function. Our findings suggest that the evolution of the trimorphic androecium is associated with division of labour in large pollen flowers and can represent a strong strategy for circumventing the pollen dilemma, optimizing the feeding function by reducing pollen grain investment from central anthers.
buzz传粉的花粉花以花粉作为传粉者的主要资源，必须应对蜜蜂对花粉粒的利用与授粉成功之间的冲突。据推测，异型雄蕊允许雄蕊之间进行分工，以此解决花粉困境。为了验证分工假说，我们选择了具有三型雄蕊群的[具体植物名称未给出]，并分析了雄蕊群的发育、花粉粒释放机制和访花者行为。我们探究了花器官的反射率，并进行了排除实验，以测试每种雄蕊形态对蜜蜂物种的吸引力。最后，我们探究了花粉粒之间的结构、超微结构和功能差异，包括不同雄蕊形态的花粉活力。由两轮雄蕊发育而来的三种雄蕊形态之间的差异，是我们研究系统中分工的首个证据。大型[具体蜜蜂种类未给出]和[具体蜜蜂种类未给出]蜜蜂积极且专门地利用来自中央孔裂花药的花粉粒，并将花粉沉积在它们身上。花器官的反射率模式表明这些大型蜜蜂以中央花药为目标，花药操纵实验也证实了这一点，即仅排除位于花中心的花药，尤其是中间雄蕊，会减少蜜蜂的访花次数。这两个结果都揭示了一种分工，其中中间雄蕊形态既负责花的吸引力，又负责花粉资源。只有最大的雄蕊形态产生可萌发花粉粒，突出了它们作为授粉雄蕊的作用。最小雄蕊形态的功能不太明确，可能代表了在花粉生产用于喂养功能方面一种节省策略。我们的研究结果表明，三型雄蕊群进化与大型花粉花的分工有关，并可能代表了一种规避花粉困境的有力策略，即通过减少中央花药的花粉粒投入来优化喂养功能。
