Floral trait evolution associated with shifts between insect and wind pollination in the dioecious genus Leucadendron (Proteaceae)

Transitions between animal and wind pollination have occurred in many lineages and have been linked to various floral modifications, but these have seldom been assessed in a phylogenetic framework. In the dioecious genus Leucadendron (Proteaceae), transitions from insect to wind pollination have occurred at least four times. Using analyses that controlled for relatedness among Leucadendron species, we investigated how these transitions shaped the evolution of floral structural and signaling traits, including the degree of sexual dimorphism in these traits. Pollen grains of wind-pollinated species were found to be smaller, more numerous, and dispersed more efficiently in wind than were those of insect-pollinated species. Wind-pollinated species also exhibited a reduction in spectral contrast between showy subtending leaves and background foliage, reduced volatile emissions, and a greater degree of sexual dimorphism in color and scent. Uniovulate flowers and inflorescence condensation are...

动物传粉与风媒传粉的转换事件已在多个演化支中被多次观测到，且与多种花部性状的特化修饰密切相关，但此类转换鲜有在系统发育框架下开展系统性评估。在隶属于山龙眼科（Proteaceae）的雌雄异株银叶树属（Leucadendron）中，从虫媒传粉向风媒传粉的转换至少已发生四次。本研究通过控制银叶树属物种间亲缘关系的统计分析方法，探究了此类传粉模式转换如何驱动花部结构与信号性状的演化，包括这些性状的性二态程度。研究结果显示，相较于虫媒传粉物种，风媒传粉物种的花粉粒体积更小、数量更多，且在气流中的传播效率更高。风媒传粉物种还表现出以下演化特征：其艳丽的承托苞片与背景植被间的光谱对比度显著降低，挥发性有机化合物释放量减少，且在花色与花香上的性二态程度更高。具单胚珠的花与花序紧缩为...