Reproductive character displacement and potential underlying drivers in a species-rich and florally diverse lineage of tropical angiosperms (Ruellia; Acanthaceae)

Reproductive character displacement is a pattern whereby sympatric lineages diverge more in reproductive character morphology than allopatric lineages. This pattern has been observed in many plant species, but comparably few have sought to disentangle underlying mechanisms. Here, in a diverse lineage of Neotropical plants (Ruellia; Acanthaceae), we present evidence of reproductive character displacement in a macroevolutionary framework (i.e., among species) and document mechanistic underpinnings. In a series of inter-specific hand pollinations in a controlled glasshouse environment, we found that crosses between species that differed more in overall flower size, particularly in style length, were significantly less likely to produce viable seeds. Further, species pairs that failed to set seed were more likely to have sympatric distributions in nature. Competition for pollinators and reinforcement to avoid costly inter-specific mating could both result in these patterns and are not mutua...生殖性状置换（Reproductive character displacement）是指同域类群在生殖性状形态上的分化程度显著高于异域类群的演化模式。该现象已在诸多植物类群中被观测到，但目前针对其潜在机制的解析研究仍相对较少。本研究以新热带区多样植物类群——芦莉草属（Ruellia）、爵床科（Acanthaceae）——为研究对象，在大进化框架（即物种间水平）下提供了生殖性状置换的相关证据，并阐明了其机制基础。通过在受控温室环境中开展一系列种间人工授粉实验，我们发现：物种间整体花部形态差异（尤其是花柱长度差异）越大，其杂交组合产生有活力种子的概率便显著越低。进一步分析显示，无法结籽的物种对在自然环境中更倾向于具有同域分布的特征。传粉者竞争与避免代价高昂的种间交配的强化选择，均可能促成此类模式的形成，且二者并非互